Types of greenhouses and frames 1

Greenhouses vary greatly in size, shape and up by paths, doors and equipment such as Shapes and styles styles have come on to the market. These type to meet the widely different demands of heaters and water tanks. The second way of Greenhouses are either free-standing or lean- usually have flat oblong wall panels but some gardeners. This wide choice is not always calculating space is to consider the growing to, that is, supported on one side by a house also are geodesic in structure, miniature helpful to the beginner, who is often thor­ area in conjunction with the height at the or other wall. Free-standing houses may have versions of the vast space-dome-like Clima- oughly confused by the variety of shapes and eaves and the height at the ridge. These two straight or inward sloping walls. Roof shapes tron greenhouse at the Missouri Botanic materials. The basic factors which must be dimensions affect first the amount of grow­ may be a simple span, hipped or double- Garden. Some of the more recent designs considered are what the greenhouse is to be ing space for tall plants, such as tomatoes, hipped curvilinear. The "mini" lean-to is a have curved glass panels and an overall shape used for, the amount of money available, and shrubs and climbers, and second ease of structure much narrower than the usual lean- that suggests the great Palm House at Kew where the greenhouse is to be erected. access and comfort in use. In general, the to greenhouse. They are useful for the small Gardens in London. Certain circular styles When buying a greenhouse, carefully larger the greenhouse the cheaper each unit garden or where wall space is at a premium. have decided aesthetic appeal and can be­ assess the amount of growing space required. of growing space becomes, though this is less The smallest ones are too narrow to enter and come a feature or focal point in the garden. There are two ways of measuring growing apparent in those models where the walls maintenance of the plants is done from the In addition they contain a surprising amount space. The first is a simple calculation of the slope inwards. All too often the beginner outside. On sunny walls overheating can be a of space, as the central path of a traditional soil or bench area available, which tells how chooses a greenhouse which in time proves problem in summer. oblong structure is done away with. At many plants may be accommodated. Simply to be too small. If cost dictates a small green­ During recent years greenhouse manufac­ present however, they are more expensive in multiply the length of the greenhouse by the house to start with, make sure it is a model to turers have been seeking more original de­ terms of growing space than structures of breadth, taking account of the space taken which extra sections can be added. signs, and as a result circular and domed traditional shape. Types of greenhouses and frames 2

Another departure from the traditional tages, and the choice must depend upon the The crucial factors in the choice of shape Mobile greenhouses greenhouse is the use of a framework of use to which the greenhouse is to be put. If are accessibility, light transmission, and sta­ Commercial growers use mobile greenhouses tubular alloy or steel supporting a cover made crops are to be grown in the border, glass to bility and durability. Commercially-available of the Dutch light type, which can be pulled of plastic sheeting. Early models, still much ground is needed for light. If most plants will greenhouses can be expected to be stable, on a system of rails over crops. These allow a used commercially, are called tunnel houses. be grown in pots, a staging is essential and the though the site must be taken into account in crop rotation program to be followed. For Smaller versions of this simple pattern are wall area beneath it can be made solid. Brick, choosing a design. Plastic-covered houses, example, salad crops can be started on one available for the amateur, and welded frame­ wood or asbestos-cement half walls provide for instance, are less durable in very windy site in spring, then left to mature in the open works in a variety of shapes are made. useful insulation, cutting the heating require­ places. Accessibility covers factors such as while the house is moved onto a new site Generally these have a traditional outline but ments of the greenhouse. A compromise is door design, which is dealt with on page 9, where tomatoes are grown. some are dome-shaped. Plastic houses are to board the north wall only, gaining some and heights at eaves and ridge pole. Low- cheaper than glass-clad ones but have draw­ insulation with little effect on light values. built houses can be raised on a home-made Frames backs in use (see pages 10 and 11). Removable wooden insulation panels are plinth of brick, wood or concrete to give It is less easy to vary the overall design of a made for some designs of greenhouse. These extra headroom. Light transmission is critical garden frame and the basic traditional shape Design can be fitted in winter and removed when only in winter and early spring, for during the is still frequently met with. This is a shallow Greenhouses can be fully glazed, or they can crops are to be grown in the bed. Kick boards summer months more light is available than oblong box with one end higher than the have one or more sides boarded or bricked should be fitted at the base of glass-to-ground is needed by the plants. Thus light is only of other and sloping sides shaped to hold a lid up to staging height. Both styles have advan­ walls to protect against accidental damage. concern when planning very early crops. or light of glass or plastic. A useful size is Types of greenhouses and frames 3

4 x 6 ft. Double and multiple frames of this Cloches design can be obtained. Variations include Until comparatively recently, cloches were double span tops and glass walls with a made as units or sections, each one like an number of different patented methods of open-ended greenhouse in miniature, fitting opening. together to cover rows of crop plants. Made Light-weight metal or plastic frames can be of sheets of glass and a variety of patented moved around the garden and placed on metal clips, they were cumbersome and ordinary beds in different positions as re­ breakable but very efficient. Rigid plastic quired. Traditional forms have permanent sheeting has largely taken over from glass for bases of brick or wood. this type of sectional cloche. The most recent Frames can be built along the sides of half- , development is the tunnel cloche made of boarded greenhouses in order to benefit from strips of flexible plastic sheeting stretched The traditional cloche (a) was made of solid anchored with wire hoops. Plastic tunnel surplus warmth from the greenhouse. over a series of wire hoops along a row and glass in a bell form. Class sheets joined cloches (e) consist of long plastic sheets The simplest form of frame is just a light, held in place with further hoops over the top. with clips can be tent-shaped (b) or barn- bent over hoops and held with more a glass or plastic panel, placed over a shallow The ends are anchored firmly by burying shaped (c). Corrugated plastic sheeting (d) hoops. Plastic sheet attached to wire pit. This allows pot or container plants to be them in the soil. Ventilation is by pushing up can be bent over rows of crops and frames forms a tent cloche (f). hardened off. the plastic on the side away from the wind. Structure materials 1

The superstructure of a greenhouse may be Unlike the wood-frame greenhouses once Metal is a good conductor of heat and cold Wood made of wood, aluminum alloy or steel. Pre- widely sold, aluminum structures do not need and for this reason, condensation drip can be However wood greenhouses are still popular stressed concrete, used for larger houses, is painting. This lack of regular maintenance is a nuisance in metal-framed houses. This heat for aesthetic reasons. The attractive colors of too thick and heavy for smaller structures. a big factor in their popularity. conduction factor also means that metal redwood, cedar and cypress fit much better Steel is also used in greenhouse construc­ houses are colder, or cool more rapidly than into the garden than the color of bright Metal tion, either totally, as in some large commer­ timber-framed ones, though the differences aluminum or steel. Most custom-built greenhouses are made of cial houses, or in conjunction with an alloy in in temperatures between the two are small. Providing a wood house is properly con­ wood or aluminum alloy. The latter is now smaller ones. The steel must of course be gal­ Unless the regular maintenance of painting structed and secured to a brick or concrete by far the most popular material, being light vanized or treated in other ways to prevent and putty renewal is considered a pleasure, base and is initially treated with a wood pre­ and strong and easily extruded into the rusting. Although generally adequate, after aluminum or steel and aluminum houses are servative (if the wood is not naturally decay- necessary shapes ready for bolting together time the galvanizing treatment breaks down much to be preferred to the various wood resistant), there is every chance it will out­ on the site. At one time, corrosion was a and rusting becomes a problem. Galvanizing houses, even those made of decay-resistant live its owner. Further painting with a wood problem, especially in areas of industrial air can also be broken down by an electrolytic redwood, red cedar or cypress, or other preservative, or better still, linseed oil about pollution and near the sea. Modern alloy is reaction when alloy and steel members woods that have been treated with wood every five years or so is a wise precaution. much more resistant so that corrosion is only touch. This factor is now well known however preservative. A metal greenhouse will allow Apart from the aesthetic considerations, likely to occur in areas of very high industrial and seldom occurs in well-designed smaller the gardener to spend more time in the wood has some advantages when it comes to pollution, which are not widespread. amateur greenhouses. greenhouse than working on it. installing extra shelving, securing wires for

Aluminum frame greenhouses are light to penetrate. The model shown has Cedar requires little maintenance and aluminum houses, but they have the maintenance-free and have narrow glazing diagonal bracing struts for stability, a sliding blends well into the garden surroundings. advantage of being easily drilled for bars, allowing the maximum amount of door and cement plinth foundations. The glazing bars are thicker than in fixings and plant supports. Structure materials 2

i climbers ,andl hooks for hanging baskets. frame on a low wall of brick or concrete. If Metal houses arcesometimes drilled for these this is not possible then redwood or metal PAINTING AND PRESERVING WOOD purposes but so often these holes seem to alloy should be chosen. The surface must first be prepared before followed by two gloss coats for maximum lx> where they are not needed and drilling it is treated. Brush down to remove dirt protection. Softwood greenhouses are extra ones is not easy without the right equip­ Cloches and grit then wash the surface and allow without question more difficult and costly ment. Extra holes also often penetrate the Class and plasticform the bulk of a cloche and to dry. Rub the wood down with a medium to maintain than the more expensive protective coatings on alloy and steel, leading are discussed on pages 10-11. Glass cloches glasspaper or wet-abrasive, which is easier hardwood greenhouses. The life of the to corrosion. are secured by various patented methods and prevents dust from flying about. When greenhouse may be doubled if the wood using stout galvanized wire or steel alloy repainting it may be necessary to strip is treated with a preservative which is Frames brackets in conjunction with wood or plastic back and reprime if the paint is blistered toxic to decay organisms. Preservatives The same considerations and comments re­ buffers. The latter method makes assembly or cracked as moisture is rapidly absorbed should be applied to the greenhouse by garding aluminum or steel and timber in the and dismantling easy but it must be used with once the skin of the paint is broken. the manufacturer before the greenhouse construction of greenhouses applies also to care when the cloche is constructed of Softwood greenhouses will need paint­ is constructed. They usually consist of frames. Since a frame is generally used in larger sheets of glass. Rigid plastic cloches are ing every other year. Use an aluminum copper or mercurial-zinc compounds, conjunction with a greenhouse it should be secured either by galvanized wire or are primer if any bare wood is to be seen after either in a water-soluble form or in a of the same materials. If wood is selected molded to shape and free-standing. Tunnel which an undercoat should be applied spirit solvent. do not sit it directly on the soil. Mount the cloches require U-shaped wires or canes.

Tubular steel frame Doors Guttering

Steel tube frames are used for film-clad and consequent repeated maintenance Sliding and hinged doors are available. Some aluminum greenhouses have built-in greenhouses. Among the cheapest frame work is to be avoided. Do not allow contact If possible, ensure that the base of the guttering, with others it is an extra. It avoids materials, steel must be galvanized if rust between steel and alloy components. doorway is flat, or provide a ramp. drips and aids water saving. Covering materials 1

Glass is the traditional glazing material for a stretched tightly over the superstructure. the type of fiberglass made specifically for Sunlight and the greenhouse greenhouse, and for a long time was the only Loosely secured material can act like a sail greenhouses should be used; the familiar Heat builds up rapidly in a greenhouse when material suitable for the job. Although plastic and, because of the movement, chafe against porch-roof material should not be used. the sun is shining and can easily reach limits sheeting has become more popular, glass is its supports during strong winds. These Perhaps the greatest advantage of fiber­ lethal to plants without ventilation and/or still the most widely used material. Most of the factors can spell disaster before the natural glass is its exceptionally high resistance to shading. Light and heat from the sun reach glass used for greenhouses is single-strength life of the sheeting is reached. breakage—a compelling reason for using it the earth as short-wave radiation, which sheet glass. However, double-strength is One advantage of polyethylene is that it is in a neighborhood of rowdy children or passes easily through glass and plastics. This preferable. From a light transmission point of so light that the greenhouse can be built frequent hailstorms. This factor, coupled with radiation warms everything it touches, such view, the larger the pane size the better. without foundations (although it must, of its good resistance to ultra-violet, means it as the floor, benches, soil, pots and even the There are also fewer heat-leaking joints with course, be anchored to keep it from being should last between 10 and 15 years. Make plants themselves, which then re-radiate large panes, although they are more expen­ blown over). Hence it can be moved around sure that it is not exposed to flame or ex­ some of this heat as long waves. It is because sive to replace if any get broken. the garden if desired. tremes of heat, because it burns readily and glass does not allow these long waves to pass A disadvantage of polyethylene is that it rapidly. through it that a build-up of heat inside the Glazing radiates heat rapidly. Because of this it is Because fiberglass is translucent, the light greenhouse results. Once shadows reach the The technique of securing the glass to the often applied in a double layer and a small admitted to the greenhouse is soft and greenhouse, or after the sun sets, heat is superstructure is known as glazing. In the fan used to blow air between the sheets in shadowless. This feature makes the panels lost via air flow through cracks and as long­ past glass was installed in overlapping sheets order to reduce heat loss. especially attractive in the West, where light wave radiation via solid walls and the basic like shingles. The side edges were slipped into Vinyl Vinyl sheet is heavier than poly­ intensity is high. framework. grooves in the mullions or were puttied, but ethylene, more durable and considerably Acrylic Semi-rigid, usually flat acrylic panels Radiation is diffused as it enters a poly­ there was no sealant along the top and more costly. If made with an ultra-violet in­ are ideal for greenhouses because of their ethylene sheeting greenhouse and the sub­ bottom edges, thus allowing a fairly free ex­ hibitor, it can last as long as five years. But it strength, light weight, resistance to sunlight sequent long-wave radiation is not trapped. change of inside and outside air. Today, the comes in narrow sheets that must be heat- and good light-transmission characteristics. For this reason, polyethylene sheeting-clad glass is used in larger pieces and is fixed into seamed, which greatly adds to the difficulty They do scratch easily, but apart from this structures, including frames and cloches, the framing members by various methods. of installation. Also, like polyethylene, it has their principal disadvantage is their very high cool down more rapidly than glass ones once In some cases putty or an equivalent material electrostatic properties that attract dust, cost. However, acrylic is worth the outlay the sun has gone, though the differences are is used. Class allows about 90 per cent of the which clouds the sheeting and therefore as it will give good service for many years. not really significant in most climates. Once sun's radiation to pass through but filters out cuts down the transmission of light. the ultra-violet part of the spectrum. Ultra­ Polyester The best known of the polyester violet light is not, however, essential to plant films is Mylar. In the 5-mm thickness used for growth and in excess it can be harmful. greenhouses, it has the advantages of being Where the sun's heat is excessive and can lightweight, it is strong enough to resist lead to scorching of plants, translucent glass damage by hail, it is unaffected by extreme can be used; but this will cut down winter temperatures and has light-transmission light penetration considerably. In temperate characteristics quite similar to glass. Mylar is, climates some form of shading is a preferable however, expensive. alternative in hot weather. Mylar should last about four years on sturdy framed greenhouse roofs and longer Plastics on the sidewalls. It will not be so effective Plastic sheets and panels perform the same when used on poorly built frames that are functions as glass in greenhouse coverings rocked by wind. and have the advantage of being cheaper and Fiberglass .Plastic panels reinforced with non-breakable. fiberglass are considerably heavier than film Polyethylene Polyethylene is applied in huge and much more durable. They retain heat sheets that make for faster glazing, but it better than other glazing materials but are has a short life span. Normally it needs to be also more expensive. replaced after one growing season. Poly­ The panels are semi-rigid and come in long ethylene with ultra-violet inhibitors lasts lengths up to 4 ft in width. The most common about twice as long. Although the material weight of fiberglass used by amateurs is 4 or does not break like glass, it is weakened by 5 oz, although heavier weights are available. ultra-violet light and often splits during gales; The panels are either flat or corrugated. The indeed on windy sites even new sheeting may latter are generally used only on greenhouse Glass should be free of flaws and bubbles, Traditional putty glazing (a). Dry methods split. It is important that the sheeting be roofs because of their greater strength. Only which act as lenses and scorch plants. (b, c) are used with metal-framed houses. Covering materials 2

the greenhouse heats up, convection cur- large, steeply inclined panes are the most rents arise and the warm air moves in a cyclic effective. fashion, varying somewhat with the shape During the winter, sunlight in northern and size of the house and the amount of regions reaches the earth at a low angle. ventilation. In theory, convection currents Therefore greenhouses with walls set at a warm the whole area, in fact there are often slight angle present a surface at right angles, small pockets of cooler and warmer air. or almost so, to the sun's rays, allowing maximum penetration. In summer the angle Light is not so crucial as the intensity of the sun­ Good glass allows about 90 per cent of total light is far greater. illumination to enter the greenhouse. This The position of the sun varies during the includes reflected light from all sources. day, moving through an arc that varies from Direct sunlight must strike the glass at a about 60 degrees during the winter months 90 degree angle for the maximum amount to 120 degrees or more in the height of the of light to enter. If the angle of the sun varies summer. Thus a flat surface receives light at from this angle some of the light will be de­ the optimum angle for only a short time. The flected. During the summer months there is round greenhouse solves this problem by more than enough light for most plants, but presenting glass surfaces at different angles during winter it is in short supply. For this so that the plants receive light of sufficient reason a fair amount of research has gone intensity throughout the year. Some green­ into finding the best greenhouse shapes for houses have been designed to rotate so that good all-year-round light transmission. As a surfaces are exposed to the sun as required. The position of the sun varies widely from rising and setting of the sun is 60°, in result round greenhouses have proved to be Round greenhouses, however, are still not winter to summer and this variation must summer 120°. In winter only the south- the best shape for this purpose. The angle at as yet readily available. Most greenhouses, be considered when planning the location facing side of this greenhouse receives which the glass is set is obviously important whether bought ready-made or built, are of and choosing the type of greenhouse. In direct sun, in summer the ends too face and among traditional greenhouse designs, the lean-to variety or tent-shaped. winter, the arc between the points of the sun at morning and evening.

Sun angles and the "greenhouse effect"

Noon, Summer. The short rays from the sun the glass. Thus the temperature rises. A Noon, Winter. In winter, the angle of the to reflect some light, which is lost. Sloped pass through the glass (a) and heat soil, plastic-clad house (b) does not get so hot glass surfaces to the sun becomes sides (b) allow light to pass through at right benches and walls. Heat is reflected as because reflected long waves can pass important as the sun angle is lower and the angles and light transmission through the long rays, which cannot pass out through through plastic, which also diffuses light. light intensity less. Vertical sides (a) tend glass is improved. Site and situation 1

All too often, the greenhouse is relegated to entrance, as is usual for sun-rooms or the Shelter Although a solid wall or a close-boarded a distant corner of the garden or to a site larger type of lean-to or conservatory. This For the free-standing greenhouse it is impor­ fence may seem the ideal, the turbulence which is far from ideal for the plants to be arrangement makes it possible to use the tant to choose a protected site or at least one factor must be taken into consideration, par­ grown. If a greenhouse is being purchased same heating system to heat both house and with some shelter from the coldest prevailing ticularly in areas frequently subjected to and particularly if the expense of heating it is greenhouse, with a saving on installation and wind. The stronger and colder the wind blow­ gales. When wind strikes a solid object such contemplated, then the best situation pos­ subsequent running costs. If the lean-to is ing across the glass, the greater the heat loss. as a wall, it swirls over the top and causes sible must be found. Failure to choose the built against a south, south-east or south­ Some estimates make the loss caused by turbulence on the other side, the distance best position could mean the disappointment west-facing wall, winter light will be good and wind as high as 50 per cent when a cold away from the wall that the turbulence ex­ of poor quality flowers, fruits and vegetables. shelter assured. winter gale is blowing. Some gardens, of tends depending on wind speed. A hedge or In many cases, space in the garden will be A greenhouse will get much more use, and course, are well sheltered by buildings and open-weave fence diffuses the wind and restricted and there will be only one possible the plants in it will get more care, if it is easy vegetation. Wind problems in such gardens breaks its main force and in this respect is site. Even so, this site can be adapted to give of access. Other considerations such as will be restricted to eddies and occasional to be preferred. Such a barrier is effective the best possible conditions. aspect and shade may take precedence, but severe storms. over a downwind distance equal to five to ten other things being equal it is best to site the Trees, even if they do not cast shadows times its height, so even if a barrier has to be Choosing a site greenhouse as close to the home as possible. over the greenhouse, can cause problems by placed to the west or south-west of the green­ Basic considerations are good light and Wherever it is placed, make sure that there rain drip onto glass, and can shed branches house to counter prevailing winds, it can be shelter from strong winds. Good light is are hard-surfaced paths leading to it. This will which can badly damage the greenhouse. sited far enough away to avoid shade especially important if plants are to be grown allow the use of a barrow to transport heavy The roots of nearby trees can also damage problems. during the winter months, and without some items such as compost and plants. foundations and intrude into planting beds. sort of wind shelter heat losses will be con­ If possible the greenhouse should be close Creating shelter If it is not possible to find a Foundation and erection siderably greater than they need be, especi­ to frames, if they are used, and the seedbed. sheltered site, a hedge can be planted, or a Once the position of the greenhouse has ally during cold spells. If the site is chosen in Often greenhouse plants will be moved to or fence erected to provide a windbreak. If this been decided upon, the terrain must be summer, and there are tall buildings or trees from the frame, and many seedlings will be is positioned at a distance of at least three examined carefully. Ideally the ground should to the south, the shadows they will cast in planted out into a frame or seedbed for times the height of the greenhouse on the be level and well drained. If the site slopes or winter must be calculated. In the latitude of growing on. Frames can be placed against north, north-east or north-west side, shading is very uneven it must be at least roughly New York City the sun at noon on the shortest the walls of a half-boarded greenhouse. will be virtually nil. leveled. When leveling the site, take care to day is poised about 28° above the horizon and all shadows are long. Winter sun angles Measuring shade areas with a sighting angle can be reproduced with the aid of a pair of calipers and a compass. A simple substitute for the calipers is two straight flat pieces of board about 1ft long, joined at one end by a single nail or screw. Open the calipers thus formed at the required angle and, keeping the lower arm horizontal, point the upper arm due south. If the part of the sky where the arm points is widely obscured by trees or buildings, then shade is likely to be a problem. To take full advantage of the light from the low winter sun, the greenhouse should be positioned with its long axis aligned east-west or as near to this ideal as possible. This posi­ tion cuts shading from roof beams and astra­ gals (glazing bars) to a minimum. An east-west position also allows the rays of the sun to penetrate at the most efficient angle (see page 11). Access There is no doubt that, to get the 1 To check if a site is likely to be shaded, 2 Place the lower arm of the sighting angle 3 The upper arm will now point to the most enjoyment out of a greenhouse, especi­ find out the lowest angle of the winter sun. on a spirit level at the planned position of lowest midday sun position. By sighting ally in winter, easy access from the house is Join two pieces of wood with a screw. Using the greenhouse. Point the sighting angle along this arm it is possible to estimate essential. The ideal is to have the greenhouse a protractor, carefully set the pieces at the south, making sure that it is exactly level. which trees and buildings will cast shadows physically attached to the house with a direct required angle. Tighten the screw. over the planned site of the greenhouse. Site and situation 2

remove and conserve the top-soil especially have been uncultivated or under grass for cement to harden before the superstructure Water supply if a glass-to-ground greenhouse with soil beds several years. For greenhouses of 10 x 8 ft or is built or glazed. The period required varies Even if it is decided to use rain water butts as is planned. Do not compact the soil when larger however a proper concrete foundation with the weather and the proportions of the a water source, these can run dry in dry spells leveling the site and erecting the greenhouse. is necessary. concrete mixture used. Allow at least 48 and there is much to be said for a per­ Undue pressure can destroy the soil struc­ Marking out the site Whether of compacted hours, more in cool weather. If glazing takes manent water supply in the greenhouse. If an ture, leading to drainage problems and loss of soil or concrete, it is most important that the place after the structure goes up this should automatic or semi-automatic watering system fertility. finished surface is level. The site should be be carried out during dry, calm weather. The or a mist propagation unit is planned, run­ If the site is wet, some sort of drainage accurately marked out using the plans sup­ same applies to the erection of sections pur­ ning water is essential. With modern plastic system should be installed. A row of tile drains plied with the greenhouse. Carefully check chased already glazed. If glazing is carried out piping and fittings the installation of a supply down the centre of the site with a sump or that the base or foundations are on the cor­ over a period of days there is much to be said is not difficult, though a professional plumber drywell at one end is usually enough, or a rect alignment, using part of a building or a for doing the roof first. This allows the wind, must be called in to make the connection concrete platform can be made with its sur­ boundary line as a fixed point. Having estab­ should it arise, to pass through the structure. to the main supply. The supply pipe is best face just above the surrounding soil. If the lished a straight line along one wall of the A half-glazed house with a strong wind blow­ laid at the same time as the foundations. If it greenhouse is to be erected on a sloping site, greenhouse, carefully measure a right angle ing on to the inside can be badly damaged. has to be added later, take care not to ensure that there is drainage to cope with for the end wall (see below right). A spirit level Class can be very slippery when wet and damage the foundations. water running down the slope from above. is an essential tool during preparation. If the ideally should be handled only in dry weather. Construct a gutter to channel water around base or foundation is not level, erection of In addition, the putty and mastic seals used Electricity the greenhouse if necessary. the superstructure may be difficult, or it will in traditional glazing do not stick satisfactorily Even if a greenhouse is not heated by it, a Bases and foundations All custom-built green­ sustain stresses and strains that later could in wet conditions. If guttering is to be fitted supply of electricity gives many advantages. houses are sold with detailed erection instruc­ lead to trouble. Most small greenhouses are to the greenhouse some thought should be It is necessary for heated propagators, mist tions. Many models have an integral or erected level, though some are provided with given to rain water disposal at this stage. Rain units, soil-warming cables and artificial illumi­ optional base, made of shaped sections of a slight fall to allow gutters to function. water butts provide a useful water reserve if nation. Lighting is a very worthwhile extra, concrete which are laid on the soil. No other Particular attention should be paid to the certain precautions are taken (see page 25). for its installation allows the greenhouse to be foundation is needed for the smaller green­ anchoring method, especially in windy sites. Alternatively, a drywell must be dug nearby used on winter evenings, adding a novel houses providing the site is firm and If sill bolts have to be cemented in place, and piping laid to it or to a nearby drainage dimension to gardening under glass. For accurately leveled. Ideally the soil should make sure enough time elapses for the ditch or watercourse. details of electricity, see page 17.

Walls, hedges and fences must be sited to winds yet casting no shadow. The fence to Mark the position of one side of the green­ square, to establish the position of one block, or preferably filter, wind, yet not cast the north can be sited closer to the house, using two pegs and a taut line. end wall. Repeat to fix the remaining shadows over the greenhouse. The 6 ft greenhouse, as it will not cast a shadow. Check that the pegs are level. Then care­ corners. Check that all eight pegs are level. hedge above is south and west of the Use hedges or openwork fences as shelter fully measure a right angle, using a T A spirit level is an essential tool. greenhouse, cutting the force of prevailing belts where possible as they filter the wind. Ventilation and shading 1

Owing to the "greenhouse effect" (see p. 11), as optional extras so it is possible to rectify when cold winds are blowing. This practice eliminate it. Before installing louvered venti­ which causes a rapid build-up of heat inside the deficiency. cuts down damaging cold drafts. All venti­ lators, check that they are reasonably draft- the greenhouse when the sun shines on it, an When warmed, it is the nature of air to lators must be easily adjustable from closed free when closed. efficient ventilation system is essential to become less dense and to rise. For this reason to wide open. This is particularly important control temperature. Ventilation is also ridge vents are all-important for releasing for the ridge ventilators which, when fully Ventilator mechanisms necessary in order to provide a supply of over-heated air. As the hot air rises up and open, should ideally continue the line of the In the small greenhouse ventilators are oper­ fresh air and to control humidity. Stale air passes out of the ventilators, fresh cool air is opposite side of the roof. This is equivalent ated by hand, being opened and secured by provides ideal conditions for the spread of sucked in through the glass overlaps, glazing to being openable to about 55 degrees. Less the same perforated bar and pin method diseases and pests. Ventilation must be con­ cracks, and around the doors. For full and than this will mean that maximum ventilation used for some factory windows. In larger sidered a factor in the maintenance of a adequate ventilation the overall area of the is not possible. However, there are practical greenhouses, particularly those with venti­ balanced greenhouse environment. It must ridge ventilators should be equal to at least difficulties to such an installation and many lators too high to reach, a variety of open­ be matched to heating, shading and the one-sixth of the floor area, more if feasible. small houses have ventilators which open ing methods are used, including cranks and control of humidity. For the smaller greenhouse alternate ventila­ less wide. A fully open ventilator at this angle gearwheels, pulleys and cords, and rack and Despite the advances made in small green­ tors either side of the ridge or at least two per is also an efficient wind trap, directing a cool­ pinion. house design few models, if any, are provided 6 ft length are usually adequate. For larger ing current downwards into the greenhouse. Automatic ventilators All the manual meth­ with enough ventilators to cope with warm structures or those used as alpine houses the This air-flow warms and rises up to exit via ods, however efficient in themselves, rely summer day temperatures without opening provision of continuous ventilators along the lee side ventilators, thus ensuring a rapid entirely on an efficient operator. Forget- the door. While using the door as an emer­ both sides is ideal. air exchange on sunny days. fulness can result in loss of or damage to gency ventilator is acceptable for some crops Air exchange and subsequent cooling is Air movement through side and ridge valuable plants. This factor, added to the and on quiet days, it should never be con­ faster if side ventilators are also fitted. These ventilators can be strong on windy days and frequent absence of the gardener during the sidered standard practice. For manufacturers, can be just above ground or at bench level. create drafts unwelcome to many tropical day, has given the impetus for the invention more ventilators means design modification Ventilators should be installed in both posi­ foliage plants and orchids. To cut down the of automatic mechanisms. Initially, and still and extra material with the inevitable in­ tions if possible. Ventilators should be posi­ force of this airflow louvered ventilators have widely used in the better-equipped nurseries creased costs. However, most greenhouse tioned on both sides of the greenhouse so been designed. However, while they can cut of commerce and public gardens, came the manufacturers can supply more ventilators that those on the lee side can be opened down the full force of a draft they cannot electric motor coupled with lifting gears and

Air flow Side ventilators

Ventilators in both roof and sides allow Ideally, roof ventilators should open to Side or wall ventilators speed air exchange closed. Louver ventilators are useful when complete air circulation within the about 55°, thus continuing the line of the and cooling. They can be conventional orchids or other tropical plants are being greenhouse. Roof vents can also act as roof when fully open. Ventilators should be (above) or louver (above right). Check that grown as they cut down, but do not wind scoops in hot weather. positioned on both sides of the roof. louver installations are draft-free when eliminate, drafts. Ventilation and shading 2

controlled by a thermostat-activated switch, Ventilator fans almost flush with the wall of the greenhouse. Plan fan installations carefully, taking more recently and now popular for the While the methods of controlling ventilation In place of glass are a series of louvers or flaps account of the capacity of the installation to smaller greenhouse, a system has been per­ described above work adequately, particu­ which hang down and cover the gap when make the necessary air changes. The placing fected which is triggered by a heat-sensitive larly in the small greenhouse, the natural air the fan is not working. Under air pressure of inlet openings is important with fan venti­ compound. The compound is contained in a currents upon which they rely are not totally from the working fan, the louvers assume a lation. Site the inlets to allow cross-drafts to strong metal cylinder, one end of which is efficient in maintaining a perfectly uniform horizontal position. The same system, but in occur, thus stimulating air movement. Damp­ closed by a plunger, the other end being climate. In larger structures in particular, reverse, can be used for the inlets at the other ing pads can be placed over inlet openings to blanked off. On heating, the compound ex­ there may be unsuspected pockets of warm end or the side opposite the fans, thus pre­ moisten incoming air in hot, dry conditions. pands, pushing the plunger forwards. This or cool air which can locally affect plant venting unwanted ventilation when the fans About 40 air changes an hour is the right rate comparatively small amount of pressure is growth. To eliminate this factor and to cut are not working. The fans are usually operated to aim for. magnified by a system of levers which open down drafts and conserve heat, ventilator automatically, being coupled to a pre-set the ventilator. Closing is gradual once the fans are used. The usual high speed fans used thermostat. Humidity compound starts to cool. Most types can be in kitchens and bathrooms are unsuitable, In general, the smaller the fan the higher it Humidistats, which work on the same prin­ adjusted to open at various temperatures. as they can create artificial drafts, and low should be set in the greenhouse wall. In the ciples as thermostats but respond to humidity The more sophisticated systems control ven­ speed fans, which can move large volumes of small amateur greenhouse, one fan installed rather than temperature, are used in com­ tilators according to a full range of weather air, have been designed. Ventilator fans are above the door is a usual recommendation, mercial greenhouses. They have the effect of conditions. Wind gauges actuate motors to also useful in plastic-clad greenhouses, where while the big 4ft fans used in commercial avoiding any excess build-ups of humidity by shut ventilators to avoid drafts. A rain water vapor condensing on the plastic may houses are set at various heights, depending turning on fans for short periods and thus gauge can be linked to ventilator controls to raise humidity unduly. A fan will prevent this upon the crop. The use of fans within the circulating the air. One effect of fans, especi­ shut down the house in the case of rain, by circulating fresh air. greenhouse, to circulate air rather than to ally in smaller greenhouses, is to dry the air. though simple temperature controls, which Installing fans Ventilator fans should be in­ ventilate, is usually coupled with heating, but If a fan is used as the main means of ventila­ will respond to increased cloud cover and stalled at one end of smaller houses or at when the artificial heat is not in use it is tion, some form of damping down or other the resulting temperature drop, produce the intervals along one side of larger structures, beneficial to leave the fan on to maintain a humidity control should be practised in warm same effect. Sunlight-operated controls are with ventilators at the opposite end or side. buoyant atmosphere which is vital for the weather. Automatic spray systems can be another refinement. Each fan is set with the blades parallel to and healthy growth of many greenhouse plants. obtained for this purpose.

Fans

Ventilators can be opened by hand (top), when heated. This expansion operates a Position a ventilator fan above the door of A louvered ventilator must be positioned at automatically (above) or by remote control plunger, which pushes the ventilator open a small greenhouse. Use only slow-running the opposite end of the greenhouse to a fan (right). Automatic systems consist of a via a system of levers. Remote systems fans designed for greenhouses. to provide a flow of air. cylinder of a compound which expands are used in large houses. Ventilation and shading 3

Shading is a greenhouse necessity that is Methods of shading warmth just when they need it most. For this Blinds Slatted blinds of wood or plastic laths easily overlooked. While in winter every effort Shading can be carried out in two basic ways, reason the use of blinds is more efficient and are best, being long lasting and rolling and is made to maximize the amount of sun re­ by painting or spraying liquid onto the glass, to be preferred. Roller blinds can be fitted unrolling easily. A certain amount of light ceived, in spring and summer too much sun­ or by blinds. Lime wash was once a standard either to the outside or inside of the green­ penetrates the blinds, but individual plants light can quickly overheat the greenhouse, liquid shading and well-diluted emulsion house, and Venetian blinds fitted to the are not harmed as the angle of the sun killing plants. Some form of shading system is paint has also been used. If applied too interior. Exterior blinds are the most effective changes slowly during the day. Also good arc- therefore essential. It must, however, be used thickly, both of these substances tend to stick as they prevent heat build-up. Blinds on the blinds made from white suffused plastic in conjunction with ventilation and watering on tight and need hard rubbing to remove at inside of the glass stop light reaching the sheeting, and Venetian blinds. Ideally, and with the aim of maintaining a balanced the end of the season. Proprietary com­ plants but the heat penetrates the glass and especially for the greenhouse owner away greenhouse environment. All too often pounds are now available which rub off easily, warms the greenhouse in the normal way. each day, the roller blinds should be auto­ shading is used simply to reduce heat and the yet are not affected by rain. All the traditional Although they can be neat and easily used, mated, the unrolling mechanism coupled to maintenance chore of watering. shading substances are likely to be thinned internal blinds can also be a nuisance where an electronic eye or thermostat. This of In greenhouses where ventilation is efficient or washed off during heavy rain and will need lots of tall plants with leaves or flowers near course adds greatly to the cost. Where auto­ there is much to be said for not shading unless replacing if hot weather continues. All liquid the glass are grown. In general, blinds fitted mation is not contemplated, the owner of the absolutely necessary. Sun-loving plants in shading should be white. Green paint—and to the outside of the house are to be pre­ smaller greenhouse can easily devise make­ particular, such as succulents, will grow more green blinds—absorb heat, while white ferred, though weather hazards must be shift shading for a few hot spells. Window­ sturdily in full light. Where a very varied col­ reflects it. taken into consideration, particularly that of like frames of strong laths or canes can be lection of plants is grown it is not difficult to The primary disadvantage of liquid shading strong wind. Exterior blinds can be rolled covered with opaque plastic sheeting or light position them so that the shade lovers are is that, during summer's inevitable dull, cool down in winter to provide a certain amount burlap and hung or clipped to the green­ behind those that need or tolerate full light. spells, plants suffer from lack of light and of protection against frost. house sides and roof, inside or out.

Methods of shading Automatic shading Improvised shading

1 Shading paint is applied 2 Exterior blinds prevent 3 Interior blinds are less Exterior blinds can be unrolled and Improvised screens can be made from to the outside of the glass heat build-up and cut down effective than exterior ones, retracted by motors triggered by light- burlap or cloth, and cloth or plastic sheet in spring. Do not apply too light. They can also be but are neat and easily sensitive devices. This is expensive, but can be pinned or stuck to the outside thickly. useful as frost protection. used. useful on greenhouses often left unattended. of greenhouses. Electricity 1

Although it is possible to run ,1 greenhouse greenhouse control panel. Choose only those without an electricity supply, lack ol power installations designed for greenhouse con­ |)uts many of the techniques of modern ditions. A control panel allows several pieces horticulture out of the gardener's reach. A of equipment to be run from one point. whole range of appliances from heaters to Fused, switched sockets are provided with an pest control equipment depends upon a independent main switch. The main power power source. Electric light also makes it cable has only to be connected, the sockets possible to use the greenhouse for more being ready wired. The equipment is then hours per day in winter. plugged in in the normal way. Always use fused plugs, if possible made of rubber Installing electricity rather than plastic. House electricity out of doors is a matter for a professional. Amateur gardeners are not Lighting recommended to attempt installation, for the Strip or bulb lighting, using heavy-duty damp- risks are great. Cables will have to be laid proof fittings, is relatively easy and cheap to outdoors unless the greenhouse is a lean-to install once a power supply is available. Light­ adjoining the home, and the environment of ing will increase the use a greenhouse gets the greenhouse itself raises dangers due to during winter, making it possible for the high humidity and damp. gardener who is away during the day to If cables have to be installed, plan the attend to the plants in comfort. route they are to take with the aid of an elec­ Lighting installations can also be used to trician. Cables can be buried or suspended speed plant growth and to modify growth Cables laid underground should be A control panel simplifies the installation of from posts. Buried cables should be sunk rates to produce special effects. Many plants protected against accidental damage while electricity in the greenhouse. All equipment in trenches at least 2\1/2 deep. Route the are very sensitive to "day length", the period digging. Cover the cable with a treated can be controlled from the panel, which has trenches where they will cause least disturb­ during which light is strong enough for growth plank or place tiles over it. fused, switched sockets. ance to garden plants, lawns and trees. When to occur. During winter in northern areas, and burying the cables, the electrician will pro­ in areas with high atmospheric pollution, this tect them from accidental damage by cover­ level is often not reached. Banks of strip ing them with a board or a row of tiles. lights are used commercially to modify the Such a protective layer will prevent damage day length and bring plants into flower out­ when digging or carrying out other cultiva­ side their normal season. Install lights about tions in the garden. Make sure that trenches 3 ft above the greenhouse bench, in banks do not interfere with drainage systems. sufficiently large to provide the light intensity Cables buried beneath paths or lawns need required. Consult specialist suppliers of green­ not be so deep, but wherever they run, a house equipment for details of light levels record should be kept of their position so and periods. Too much light, or too long a that if the layout of the garden is changed "day", is often worse than too little, as many the gardener is aware of the exact position plants have very specific requirements. Use of the cables. mercury vapor lamps, as the type of light they Cables taken overhead must be fixed to a produce is best for plant growth. Banks of stout wire supported on poles well above the fluorescent tubes can also be used, mounted ground. Keep the cable clear of trees which 2 ft above the bench. may chafe it. The gardener may be able to save on the electrician's bill by doing un­ Other electric equipment skilled preparatory work such as digging Propagating equipment, watering devices trenches or erecting poles. Consult the elec­ and ventilation equipment are described on trician and agree on exactly what is to be the appropriate pages. Equipment used in the done by whom before starting work. greenhouse must be made for the purpose. Thermostats should be set to the Fan heaters can be used to back up other Do not, for instance, use domestic cooling temperature required in the propagating heating systems or as a system on their Power points fans and fan heaters as they may be affected case or soil cable unit. Check the own. Use only those designed for Inside the greenhouse, the power cable by the damp atmosphere in the greenhouse manufacturer's literature for the greenhouses, which can withstand damp. should terminate at a purpose-designed and become dangerous. temperature range the appliance controls. Heating 1

In the cooler temperate regions where frost Thus if the likely minimum temperature of the occurs regularly in winter, sun heat alone is area is — 2°C, and a cool greenhouse is plan­ too weak and unreliable for the successful ned the temperature must be raised by 6°C growth of tender plants under glass. There­ and the heating system must be adequate. fore to get the best out of a greenhouse an Greenhouses have higher heat losses than artificial heat source must be installed if only other, more solid, structures and are more to keep the minimum temperature above the prone to drafts. Also, heat is lost quickly frost limit. An alternative is to use a heated through glass so cold spots can easily develop propagating case as a "greenhouse within a if the heating system is not carefully designed. greenhouse" to allow seeds and cuttings to be A single stove or radiator placed in the center started earlier than in the greenhouse itself. of the greenhouse will not necessarily warm It is possible to run a greenhouse without any the whole air space, which is the reason why heat—see the Cold Greenhouse section pipe systems are popular. To check for cold (page 64)—but a heat source which, com­ areas, place several maximum-minimum bined with insulation, maintains the temper­ thermometers at intervals around the green­ ature above freezing, is almost essential. house and leave them overnight. Alter­ The first question to ask when planning a natively, use a single thermometer, placing it heating system is what level of heat is needed. at different points on nights with the same or Two factors must be taken into account. They very similar air temperature. are the prevailing weather conditions in the Before calculating heat needs, check what locality and the needs of the plants to be can be done to improve the insulation of the grown. There are certain levels of tempera­ greenhouse. Double glazing is the most ture which must be maintained if various effective means of cutting heat loss. Per­ types of plants are to be grown (see Intro­ manent double glazing is heavy, costly and duction, page 2). Refer to the map, right, can interfere with light transmission, but is for the lowest likely temperature. Consider becoming a more attractive option as better the modifying effects of height, exposure and systems are designed and fuel costs continue proximity to the coast, which can raise or to climb. Alternatives to permanent double lower minimum temperatures. glazing are temporary plastic sheet double Once the minimum temperature needed glazing or the use of insulating panels on the in the greenhouse has been decided, the lower parts of the greenhouse sides. temperature increase required can be calcu­ Drafts should be stopped wherever pos­ lated. This is the number of degrees that the sible, not only because they increase heat temperature must be raised above the likely loss but because drafts can interfere with the minimum to be encountered in the locality. working of heating systems.

CALCULATING HEAT LOSS

Use the map right to establish the tem­ a heating system capable of raising the perature rise required. Then calculate the temperature by 4,000 BTU's- is needed. rate of heat loss. First measure the glass Heaters and fuels have their heat outputs area of the greenhouse in square feet. Each quoted in BTU's/hour so the size of heating square foot of glass will lose 1.13 British installation needed can be calculated. Thermal Units (BTU's) of heat per hour for Bear in mind additional heat loss from each degree F of temperature difference wind, through gaps in the structure and The map above divides North America of growing season. When calculating between inside and out. Thus if there is through necessary ventilation. Measures into ten zones of hardiness. This zone greenhouse heating needs, use the map 360 sq ft of glass and the temperature taken to reduce heat loss such as double system was devised by the Arnold Arbor­ to assess the local minimum temperature. difference between inside and out is 10°F, glazing reduce the amount of heat needed. etum at Harvard, and is widely used by The difference between the expected mini­ the heat loss is 4,068 BTU/hour (360 x 10 Heat loss varies with material: the all-glass scientists and gardeners. The zones are mum and the temperature desired in the x 1.13). Thus in order to maintain a tem­ figure quoted gives a slight over-estimate defined in terms of consistent average greenhouse is the necessary temperature perature 10°F above the likely minimum, for a part wood or brick house. annual minimum temperature and length increase the heating system must provide. Heating 2

Air circulation Supplying oxygen to heaters

Wind can lower the temperature of the Allow a gap between benches and stagings Leave a ventilator open while combustion Alternatively, install a door or wall vent exposed side of the greenhouse. Adequate and the sides of the greenhouse to permit heaters are in use. Avoid drafts over which will provide enough oxygen for air circulation helps to avoid cold spots. air to circulate. plants. combustion without creating drafts.

Checking for cold spots Insulation

Check for cold spots in the greenhouse by greenhouse or, if only one is available, vary Insulation can be applied in the form of using tacks or a staple gun. Remove using one or more maximum-minimum its position noting minimum temperatures special panels (left) or plastic sheeting, right, insulation as soon as the weather moderates thermometers. Place them around the on nights of similar outside temperature. which should be fixed in double layers for it will impede light transmission. Heating 3

Solid fuel piped hot water systems time. Large installations may have a main burning correctly, dangerous carbon mon­ Natural gas heating Heating water by burning solid fuel is a cheap constant-level system of the water tank and oxide fumes will be given off instead of carbon Natural gas burnt directly in special heaters method of heating a greenhouse. Modern ball-valve type. dioxide and water vapor which is beneficial to is very efficient. Its by-products carbon furnaces burning coal, anthracite, and other plants. Ensure that the flue fitted to the fur­ dioxide and water vapor which enhance the special fuels are designed to reduce stoking Oil-fired piped hot water systems nace is tall enough to carry fumes away from greenhouse atmosphere make the com- and the clearing of ash to a minimum. Many Solid fuel furnaces may be adapted to burn oil the greenhouse. Regular maintenance should mercial greenhouse practice of atmosphere have quite good thermostatic control but or a purpose-built system can be installed. be carried out on all furnace systems to avoid enrichment, which encourages the plants to are not so accurate as the more easily con­ Oil-fired systems can be thermostatically problems with fumes and fuel wastage. grow, available to the amateur gardener. As trolled fuels such as electricity and gas. Water controlled: an efficient thermostatic control the burner is sited inside the greenhouse, heated in a boiler within the furnace circu­ system reduces the amount of attention Linking greenhouse and domestic systems regular maintenance is necessary in order to lates through a system of pipes. The pipes, required to maintain a constant temperature. Where a lean-to greenhouse or sun room avoid possible emission of poisonous gases which must rise gently from the boiler, should Large, specially manufactured oil-fired in­ is to be heated and a hot water radiator such as carbon monoxide. The natural gas be of narrow-diameter aluminum rather than stallations are highly efficient and automatic. system is used in the home, it is sometimes systems on the market are thermostatically the large-diameter cast iron type. Furnaces possible to link the two. However, it is controlled and fully automatic, with a safety are rated in terms of heat output as BTU's/ Gas-fired piped hot water systems advisable to consult a heating engineer first, valve which prevents the main supply from hour. Choose a furnace large enough to heat Gas furnaces are easy to operate and may be and best if possible to incorporate the green­ being turned on unless the pilot flame is the greenhouse to the desired temperature fully automatic, being controlled thermo­ house heater in the home system when it is alight. It is more convenient to use a piped (see page 18). Only the fuels recommended statically. Care should be taken to site the installed rather than to add later. Problems natural gas supply in conjunction with a by the maker must be used. The pipes are furnace where its fumes will not be carried can arise with a linked system because special greenhouse heater which is portable best filled with soft water such as rainwater, into the greenhouse. Gas fumes can be greenhouses need heating at night, whereas to some extent. Bottled natural gas such as and will have to be topped up from time to dangerous to plants. If the furnace is not homes are heated during the day and evening. propane or butane tends to be expensive

Piped systems circulate hot water from a lower pipe to the furnace. This kind of The small-bore piped system uses narrow pipes and a circulating pump may be furnace through pipes laid around the system, using large-diameter cast iron pipes, aluminum piping. Because of the extra needed. A header tank (illustrated) tops up greenhouse. The hot water rises from the is less efficient than the small-bore system, friction in smaller pipes, the water does not the water in the system. Such furnaces boiler, slowly cools, and returns via the right, which has mostly superseded it. rise by convection as freely as in large can be fuelled by solid fuel, gas or oil. Heating 4

although it is convenient where piped produce water vapor as they burn which Siting a boiler supply is not available. Propane is advisable keeps the greenhouse atmosphere moist, when the storage bottle is kept outside as although ventilation is necessary at times as butane does not readily volatilize in cold the atmosphere may become excessively weather. The larger the bottles or cylinders, humid. When combustion is taking place the the more economical is this type of heating. greenhouse must be ventilated to provide an oxygen supply. Keep the heaters clean and Kerosene heaters the wick trimmed according to the maker's Kerosene is the simplest form of heating to instructions. Features to look for when buying install. Choose a heater that is designed for a kerosene heater are stainless steel lamp the greenhouse, as some household kerosene chimneys, fuel level indicators and large, heaters give off fumes deadly to plants. separate fuel tanks to make filling easier and Greenhouse heaters are specially designed to less frequent. reduce the risk of fumes and are often equipped with tubes or other devices to Electric heating systems distribute the heat evenly around the green­ Electric heating is the most efficient and house. They are, however, difficult to control effective. It is easy to control, clean and is the thermostatically. A flue is a desirable feature, safest for use with plants as there are no since some models may tend to produce fumes. It must be fitted by an electrician as harmful fumes. Some have hot water pipes the combination of electricity and damp can Fumes from a furnace can harm plants. Site downwind, so that the prevailing wind as well as hot air ducts. Kerosene heaters be lethal (see page 17). it therefore outside the greenhouse and carries smoke and fumes away.

Where pipes run across a doorway, lay Electric tubular heaters distribute warmth Natural gas heaters heat the air by the Kerosene heaters must be carefully metal grilles above them to allow heat to evenly in the same way as piped hot water burning of a gas which is harmless to plants maintained to avoid harmful fumes. rise yet protect the pipes from damage. systems. They can be mounted in banks or if the burners are correctly adjusted. Piped Choose a model with a large, easily-filled installed singly in greenhouse cold spots. or bottled gas can be used. fuel tank and a fuel level indicator. Heating 5

There are many different types of electrical Soil heating cables heating apparatus especially developed for There are many advantages to the gardener greenhouses. Tubular heaters have a similar in warming the soil from below. Crops may be capacity for even distribution as hot water raised earlier than normal and cuttings and piping systems. Position along a side wall of seed germination should be more successful. the greenhouse in a single line or group There are two good methods of warming together at points around the greenhouse to the soil using cables. The first utilizes bare give more heat to colder areas. cables buried 6-9 in below the surface of the There are compact fan-assisted heaters soil with low voltage current passed through which are easily moved and will spread the them by means of a transformer to step down heat over the whole area of the greenhouse. the primary voltage. Alternatively, insulated They may also be used to circulate cool air soil-heating cables are used in conjunction when heat is not needed. Thermostatically with the full house current buried 6-9 in controlled fan heaters will accurately control below the surface. temperatures to within one or two degrees The soil is excavated to the required depth with no waste of fuel or heat and need little and a layer of sand spread over the bottom maintenance. Fan heaters circulate air, keep­ of the trench and raked level. The required ing the atmosphere buoyant and reducing length of cable, as recommended by the the chance of fungal disease. The best type of manufacturer, is laid over the surface in fan heater has separate thermostats con­ parallel lines as evenly spaced as possible. trolling the fan and the heat, supplying heat The cable is then pegged in position using when it is needed. When the fan is switched galvanized wire pegs. off the air will remain relatively motionless There is no need for special precautions to 1 Remove the border soil to a depth of 2 Lay soil heating cables on the soil except for convection currents. The advant­ protect the wire when using a low voltage. 9 in. Pile the border soil to one side and surface. Space the cable in a series of loops age of this system is that there will be inter­ However, 115 and 230-volt cables can be rake over the base of the trench produced. 4—6 in apart. Do not let the loops touch. mittent air circulation with little heat loss. dangerous if accidentally severed. It is there- Peg the cable down with staples. The fan-heated greenhouse can be safely left closed during cold weather as there is no HEATING COSTS contamination of the air and no need for extra ventilation. At a time when the relative prices of the Convection heaters are another type of various fuels are fluctuating, it is impossible efficient electric heater. They consist of a to give a realistic indication of what it cabinet with holes at the top and bottom costs to heat a greenhouse. Two key with heating wires inside which warm the air. points emerge from any study of heating The warm air rises and flows out at the top costs. First, waste of heat, through inade­ causing cold air to be drawn in at the bottom. quate insulation, drafts and poor ad­ In this way convection currents cycle the air justment of heating systems, is a major around the greenhouse. factor in most fuel bills. Second, the effect Storage heaters can be economical using of raising the greenhouse temperature the off-peak rate for greenhouse heating. from cool to warm level is to double bills. This type of heating is, however, difficult to Therefore the decision to grow warm control thermostatically. There will some­ greenhouse plants is one that must be times be too little and sometimes too much taken with an eye on the cost. Also, heat. They are best used for background careful management and heat conserva­ warmth in conjunction with a main heat tion can make all the difference to the source keeping the maximum temperature economics of greenhouse heating. The thermostatically. An accurately controlled flexibility of the various fuels must be electric heater can be used to maintain the considered as well as cost. Electricity, maximum temperature level with a kerosene especially when used to power fan heaters, 3 Replace the border soil and rake it level. 4 Connect the soil heating cable to a heater for background warmth. The advan­ is very flexible and little energy is wasted Water the bed lightly. Damp soil conducts thermostat, if one is supplied with the cable tage of using a combination of heaters is that providing unwanted heat. heat better than dry. kit, or direct to an outlet. Carefully follow the more expensive fuels are conserved. the maker's instructions on installation. Heating 6

lore a good plan to lay ,1 length ot galvanized accurate thermostatic control is possible mesh over the cable. Spread sand over the with electric heaters, and for this reason SOLAR HEATING mesh and then replace the soil. Plug the other types of heater use electricity to All sources of heat are solar in the sense Heat storage cable into a waterproof outlet which is operate motors or electro-magnets which that their fuels are derived, however placed well above the level of the soil where regulate the flow of fuel. A thermostat usually distantly, from the power of the sun. Oil, there is no danger of it getting wet. has a graduated dial which is set to the coal, and gas, and electricity generated Soil-heating cable kits are available com­ required temperature which the thermostat from them, are fossil fuels produced by plete with thermostats, although the ther­ will then maintain, if the heating system is nature from sun power. Because these mostat is not essential. Soil-heating installa­ powerful enough. fuels are expensive, increasingly scarce tions vary in power. They usually provide a and liable to interruptions in supply, temperature of 16°C/60°F. Conserving heat in the greenhouse many attempts have been made to har­ Heat will be lost through broken and cracked ness the sun directly. Two linked problems Thermostats glass, ill-fitting doors and vents, which must immediately arise: timing and heat stor­ The various heating systems described may be repaired or improved. age. The sun tends to shine when heating all be controlled by special greenhouse Lining the greenhouse in winter with is least required, so some means of heat thermostats. A thermostat is a device that polyethylene sheet to give a "double glazing" storage is essential. None of the systems controls the temperature of the atmosphere effect will help enormously (see page 22). Use available can be said to overcome these in the greenhouse by regulating the fuel the thinnest and clearest polyethylene sheet problems so completely that they can be supply to the heater. Two strips made of available. It is the static air trapped between recommended as a sole system of heating. different metals, joined together within the the plastic and the glass that forms the insula­ Solar heating has two uses at the present thermostat, expand and contract in response tion—so do not leave gaps. So that vents can stage of development: as a back-up heat to changes in temperature. The movement be opened, line them separately. source and as an area for experiment by of this bi-metallic strip switches electrical Burlap or old blankets placed over the technically-minded gardeners. The illus­ Warm air is sucked by a fan down a duct contacts which control the flow of fuel, or the roof at night in extremely cold weather will trations on this page show the principles from the roof space, where sun heat is flow of air to solid fuel, thus regulating the conserve heat. They must, however, be behind some of the solar heat methods greatest during the day. Rocks below the speed at which the fuel is burnt. Very removed in the morning. in use. floor store heat. At night, the fan reverses.

Warm-air duct heating Water panels and heat storage Solar furnace

Polyethylene ducts, which may be greenhouse eves. First used in commercial Water is pumped up and flows over roof The sun heats air behind the glass wall, perforated, distribute heat given out by an greenhouses, they are an efficient means of panels. The sun heats the panels and the causing it to rise. Warm air flows into the electric fan heater or a gas heater fitted distributing heat in larger greenhouses. water, which is stored in an insulated tank. heat storage of rocks, which are heated. At with a fan. Such pipes can be installed At night, flaps are opened to let heat out. night warm air is pumped from the storage. either below benches or along the Water supply and watering 1

Every greenhouse should have a piped supply can be installed over the tank to replenish for watering plants on shelves and lor Automatic watering: Pipe systems these of water, unless it is very small or is close to it when rain fails. If water reserves of these measuring out liquid fertilizer, fungicides and methods of watering involve piping and the house or an outside faucet. Despite the kinds are contemplated, it must be borne in insecticides. A gallon can is the most useful. finer tubing or nozzles. Trickle systems are the contrary preferences of some gardeners, mind that mosquitoes and other pests will It should feel balanced and comfortable to the most popular. In its simplest form this is city water is perfectly acceptable for plants, breed in static water. Water from tanks can grasp. It should have a tapered extension piping perforated at intervals and so arranged and, unlike rainwater, the piped supply is also act as a distributor of fungal and bacterial spout for plants at the back of benches and that a perforation is over each pot, or by unlikely to fail. However, guttering is useful plant diseases. on shelves, and a fine rose for watering newly- each plant to be watered. Somewhat more in itself in preventing drips from the green­ If running water is installed in the green­ sown seeds or pricked-off seedlings, or for sophisticated versions have nozzles or a house and it is sensible to store the water the house, make sure the water piping is well damping down floors. If high-level shelving length of tubing from each perforation. In the gutters channel. Rainwater storage requires buried to prevent freezing. Install the pipes, or hanging baskets are fitted, obtain a so-called spaghetti system a sheaf of very careful planning and attention to hygiene if which can be of modern plastics with com­ smaller 1/2 or 3/4 gal can with a long, curved small-bore tubes runs from the end of a water butts are not to become havens for pression fittings, when the greenhouse is spout. Cans are made of galvanized or hose. Each tube is then led to a pot and waterborne pests and diseases. being built. Fit a faucet chosen to suit the enameled metal or plastic, the latter being clipped into place. These methods can be If stored rainwater is to be the only source watering equipment likely to be used. A now the most readily available. Plastic is set to trickle indefinitely, or the water supply of supply, at least two 60 gal butts will be range of modern hose couplings and connec­ cheaper than metal and lighter to handle. can be set to a solenoid valve and linked to a needed for a fully-stocked 8 x 8ft green­ tions for automatic watering devices is Automatic watering: Capillary benches time clock to run at set intervals. house, and even then the reserves will be available, allowing several watering systems Watering plants properly by hand can be a If a slow non-stop trickle is used the pots used up during a dry spell. Butts should have to be used at the same time. time-consuming job, requiring knowledge must be inspected regularly. Large, vigorous tight-fitting lids to keep out leaves and other and experience. There are several methods of plants may need more water than the trickle debris which can foul the water. Two or Watering systems watering plants automatically, whether in can deliver, and will suffer as a result. more butts can be connected by overflow Once a supply of water is assured, watering pots or beds. Where a large collection of pot Overhead sprinklers can also be used on an pipes to store surplus water. An alternative to systems can be chosen. These range from plants is maintained and especially if the automatic basis and for plants which need butts is a tank within the greenhouse or simple cans to automatic devices. owner has to be away during the day, a a high humidity they are ideal. Care must be even under the floor, with pipes leading from Cans Even if automatic watering devices are capillary bed system is a worthwhile invest­ taken, however, to see that all plants are the guttering. With this arrangement, a faucet favored, a watering can will still be necessary ment. This method works on the capillarity getting an adequate water supply. The dense of moist sand. That is, water is sucked up or broad foliage of some potted plants can through the tiny spaces between the grains effectively prevent enough water from reach­ WATERING CANS of sand through the drainage holes into the ing the rootball beneath. pot. Line a deep bench top with heavy gauge While all these self-watering methods are plastic sheeting, and fill with washed sand invaluable to the greenhouse gardener, they to a depth of 2-3 in. Special trays can also must be used intelligently. As with all forms be used. The sand is kept continually moist of automation, they are non-selective and on the surface but not waterlogged, either this is a disadvantage where living organisms with a watering can or an automatic device. are concerned. Every plant will get the same The simplest of these is the inverted demi­ amount of water whether it needs it or not. john or header bottle in a shallow reservoir, Some will respond by growing lush and out of which overflows directly onto the sand character, others may become waterlogged or into connecting guttering. A more fully and slowly die. Where a wide variety of plants automatic system uses a header tank con­ is grown, they must be inspected regularly. nected to a piped water supply and fed to Over-wet plants must be taken out of the the sand bench via a ballcock valve. The pot automatic system for a while to dry out, plants, which should not be crocked, are while dry ones must be given extra water pushed into the top inch of the sand with a by hand. screwing motion so that sand is forced into the drainage hole or holes and makes Humidity contact with the soil. Water is taken up into Although water is primarily used for keeping the soil by capillary action. the roots moist, most plants appreciate or Watering cans should be durable and shelves and hanging baskets to be easily An alternative to sand is the so-called need humidity in the air, at least when in full well-balanced. A long, possibly sectional, reached. A fine rose will be required for capillary matting which is kept wet in the growth. This too can be provided by automa­ spout is useful in a crowded greenhouse watering seeds and delicate seedlings and same way. It can however, become clogged tion, using overhead or near-ground nozzles and a small can allows plants on high rooted cuttings. with algae after a time and then needs such as those used in mist propagation careful washing or replacing. systems (see page 30). Water supply and watering 2

Storage butts Internal tanks Connecting fittings Header tanks

Water butts should have tight-fitting lids. Guttering can be led into the greenhouse Special fittings replace faucets and allow Header tanks and bottles supply water to Two or more can be connected by pipes. to fill an internal water tank. Fit a tight- several appliances, such as hoses and a capillary and trickle irrigation systems by Faucets allow cans to be filled. fitting cover to keep insect pests out. header tank, to be used at once. gravity.

Capillary bench Capillary matting

The capillary bench watering system plants take up water from the sand through An alternative to a sand bench, capillary Water can be supplied manually or by a consists of a polyethylene-lined tray filled the pots' drainage holes. Push the pots matting soaks up water which is then header tank or bottle. The matting becomes with sand. The sand is moistened and the into the sand with a screwing motion. taken up by plants by capillary action. clogged with algae after a time. Water supply and watering 3

Watering allowed almost to dry out (or dryish potting Spray lines Trickle irrigation All watering under glass requires care, espe­ mixture can be used at the outset). Each pot cially that of plants in containers. In the is then weighed in the hand, watered tho­ beginner's greenhouse at least, more plants roughly and checked again. A method are likely to suffer or die from lack of, or too formerly much used involves the use of a much, water than succumb to pests and tapper, easily made from a length of cane diseases. Watering is a skilled operation, not and a small block of wood about the size of even all professional gardeners fully master it. a cotton reel. Each pot is rapped smartly in Like so many other aspects of gardening turn and if a ringing tone is given out the root under glass, it is essential to get to know the ball is dry and watering is needed. A dull, plants well. In time, personal observation hollow noise denotes that the rootball is will provide the experience that is required to moist. This only works with clay pots. judge accurately the needs of each plant at The above methods can be used success­ any time of the year. fully on healthy actively growing plants. They are less easily applied to dormant or resting Watering containers plants which require keeping barely moist. Water plants in containers by filling the space Provided a free-draining potting medium is between the soil surface and the pot rim with used, ideally a loam-based mixture, applying water, thus ensuring that the whole of the just half the usual amount of water at each root system is moistened. Frequency of application is usually successful. All-peat pot­ watering depends on several factors, notably ting mixes shrink away from the sides of the the vigor of the plant, temperature, type of pot when kept too dry and much of the soil, and the container. A fast growing, well subsequent water applied runs down the Fine sprays of water directed by nozzles Trickle systems supply a small amount of rooted plant will probably need watering sides. To overcome this difficulty the plants onto plants are an efficient way of both water continuously to each plant. Check each day in summer, perhaps even twice should be stood in trays of water so that the watering and raising humidity. plants regularly. daily during a hot spell. In winter the same bottom half of each pot is submerged. Unless plant may need watering only once or twice a the soil is dust-dry, a few minutes in water Trickle irrigation—spaghetti week, or even less if it has a definite resting will suffice to moisten it adequately. period. If in doubt as to when a plant needs water, there are several useful observations that can Watering beds be made and points to check. Wilting or Beds and borders in the greenhouse are flagging of the plant is very obvious when in watered in much the same way as those in an advanced state but the observant gar­ the outdoor garden and it is even more dener will note the slight drooping of soft important to use a rose or sprinkler on the stem and leaf tips which precedes this, can or hose. This prevents panning of the denoting a need for water. Whatever the soil surface and unsightly soil-splash on soil mixture used it is always paler in tone lower leaves of small plants. As with pots, when dry. When this state is reached in a beds must be attended to regularly and clay pot, watering is required. In a plastic pot thoroughly. It is all too easy to think the bed however, this indication is not so reliable, as has been well watered when in effect it is containers of this sort are not porous and the still dry several inches down. Many a crop soil stays more moist below the surface layer. of grapes, peaches or tomatoes has been If the plant is not growing vigorously or the spoilt for this reason. The equivalent of at weather is cool, it is advisable to scratch into least one inch of rain should be applied each the surface of the soil with the finger tip. time. To get a rough idea of this amount, If the top 1/4 in of the soil is dry, then water­ stand a straight-sided container on the bed ing should be carried out. An estimate of during watering. When an inch is measurable the weight of a pot full of soil can also in the bottom, leave for at least an hour then be used as a guide. To enable the weight dig a small hole about 6 in deep and if dryish The so-called spaghetti system works on the coupling, deliver water to each plant. A differences to be recognized, a range of pots soil shows at the bottom of the hole, water same principle as the trickle system. header tank can be used to give a should be filled and firmed as for potting and again. Flexible tubes, attached to a central continuous supply, or a timeswitch fitted. Benches and staging 1

Kent lies and staging of some sort arc used in maintain plants at bench level—most heat, cold and sunlight, and that plants Uses for solid benches A solid top to the most greenhouses, the only exceptions being benches and stagings are 2 1/2 ft high. The placed on them will need extra care. Finally, bench or staging allows beds of soil, sand or those houses used entirely for growing crops plants are also nearer eye level, allowing ensure that there is easy access to all plants. gravel to be formed. These can range from in the border soil, those devoted to tall con­ them to be better appreciated. Benches and staging should be no more than thin layers of gravel on which containers are tainer plants and possibly those lean-tos Other kinds of structure such as shelves, 4 ft deep, and shelves, pot holders and hang­ stood, to aid drainage and increase humidity, which are primarily used for growing fruit pot holders, orchid baskets, and hanging ing baskets should be placed where they do to 4-6 in deep beds of sand or soil. Such beds against the rear wall. Benches are less per­ baskets for ferns and trailing plants can also not impede normal work in the greenhouse. are essential if mist propagation or the use of manent than stagings, a term used to refer be fitted into the greenhouse. Take care not Keep hanging baskets, for instance, above soil heating cables are to be practiced. to robust long-term constructions often to over-crowd the greenhouse, for too many normal head height unless they are sus­ Gravel trays are watered in summer with the supporting raised soil beds. structures will cut out light, impede air circu­ pended over a bench or other area away aim of increasing humidity. Solid-topped The use of benches and staging has several lation, and allow high-level plant containers from the central path. Shelves can be placed benches are also needed if trickle irrigation advantages. They multiply the amount of to drip onto those below. across the end of the greenhouse, opposite systems are contemplated. Hydroponics sys­ useful growing space available, as the area the door, it they do not obstruct side benches. tems, which rely on a flow of nutrients in underneath them can often be used. This is Positioning benches liquid form, need solid benches. Shallow especially true in glass-to-ground houses, Take account of the aspect of the greenhouse Types of bench and staging metal trays can be used to convert per­ where enough light will penetrate the area when planning the position of benches and The first choice to be made is between solid forated benches into solid ones. beneath the benches to grow crops such as staging. If the axis of the house is east-west, and perforated tops. Both have their advan­ Materials The choice is between metal lettuce and to raise seedlings in boxes and then one bench on the north side is ideal, as tages, and the choice depends to a large frames, wood frames and permanent brick pans. In half-glazed houses the area beneath it does not block light. The south soil bed can extent upon the crops to be grown and the or concrete stagings. Metal and wood frames the staging can be used for forcing crops such be used for crops, and adequate light will type of cultivation to be carried out. Air can be fitted with perforated or solid tops. as rhubarb and seakale and for storing dor­ reach plants on the bench. Place high-level circulation around benches is not so critical Some benches are removable, giving flexi­ mant plants during winter. Plants grown on shelves where they will not cast shadows over in summer, when more ventilators will be bility in the arrangement of the greenhouse. benches are likely to receive more light than other plants for an appreciable portion of the open. Then, perforated benches may be Wood will need to be thoroughly cleaned at those placed on the floor or grown in soil day. Bear in mind that shelves raised near to covered with plastic sheet or metal trays to least once a year as it can harbor pest and beds. It is also easier to water and generally the roof glass will be subject to extremes of allow solid-bench techniques to be used. disease organisms.

Types of staging

Staging can be timber or metal-framed, or and in summer can be covered with plastic maximum air circulation allowing heat to releasing at night heat absorbed during the supported on brick or concrete piers. sheet which can be spread with moisture- circulate. Metal trays can be laid on the day. Concrete is also strong, and can Slatted wood staging (a) is traditional and retaining vemiculite, gravel or peat. Net- staging and filled with gravel (c). Solid similarly support raised soil beds and heavy attractive. It allows air circulation in winter, topped stagings (b), with metal frames, give brick staging (d) acts as a heat reservoir, pots, but it retains less heat than brick. Benches and staging 2

Shelves Displaying plants

1 Metal or wood shelves can be fixed to 2 Tiered staging displays large numbers of Pot holders allow plants, especially trailers, Hanging baskets can be suspended from glazing bars on the sides and roof of the pot plants attractively. It is available in to be mounted on the greenhouse sides. brackets mounted on walls or from the greenhouse. Use special clips on aluminum wood or metal and can be placed on the They can be bought or improvised from greenhouse roof. Use those fitted with drip frames. Make shelves at least 6 in deep. ground or on staging. bent wire. trays if they are placed above other plants

Displaying orchids Shelves under staging Hardening-off shelves

1 Many orchids grow best in perforated 2 Epiphytic orchids can be grown on thick Shelves can be mounted under staging in Some greenhouses are equipped with containers or wooden baskets, which can pieces of bark. Wrap roots in compost and glass-to-ground houses, especially on the opening panes allowing flats of plants on be suspended from the greenhouse roof. wire the plant and rootball to the bark, south side. Use shelves for pots of bulbs shelves below the staging to be slid into the (See pages 84-85) which is hung from the roof. during their dormant periods. open by day and returned at night. Benches and staging 3

Solid brick and concrete stagings can he from the roof beam if there is enough head­ built as part of the structure of half-glazed room. Proprietary fastening systems have WIRING A WALL greenhouses with a brick base, lhey are very brackets which can be adjusted to the dis­ strong, and also have the advantage of in­ tances between the greenhouse frame bars. creasing the amount of heat the greenhouse Shelves should be wide enough to take the can store and release during the night. Sun pots envisaged, strong, and easy of access. shining through the glass strikes the staging Bear in mind the need to water the plants. and heat is stored in the same manner as in Tiered shelves Banks of tiered wood or metal a brick or stone wall. This heat is given off shelves can be installed in place of normal during the night, moderating the temperature benches, or can be mounted upon the bench drop in the greenhouse. Brick is a much more itself. They are of most use where large num­ efficient storer of heat than concrete, and bers of ornamental pot plants are grown, therefore brick structures should be chosen allowing the largest possible number of if heat storage is an important factor. Choose plants to be displayed. hard-faced bricks which are less porous than the normal sort. These are easier to scrub Hanging baskets down and less likely to harbor pest and Hanging containers may be essential if many disease organisms. trailing ornamentals are grown, and in any case such containers are attractive. Baskets Bench-top beds are made of metal, or preferably plastic- Soil beds at bench level are described on covered metal. They are filled with soil mix page 46. They need strong brick or concrete and lined with moss (see page 54). Place them staging and by their nature are permanent. carefully where drips will not be a problem, Rear walls of lean-to greenhouses can be wall and make maintenance and repair Less permanent beds can be formed by add­ and ensure that fastenings are strong enough used to grow fruits and ornamental to the framework difficult. ing raised edges to solid-based benches. Such to support the combined weights of con­ plants. Careful preparation pays dividends First scrub down the wall with water and benches can be covered with soil, sand or tainer, plants and wet soil. later on, when the plant will cover the a dilute horticultural disinfectant to kill gravel. The use of soil heating cables re­ Pots can be suspended in wire or cord quires a bed of sand or soil 4 in deep, in which "cradles", or in the decorative purpose-made the cables are buried. Power cables of special holders designed primarily for house plants. type are used to raise the sand temperature Drill plastic pots to take the wire; clay pots to 43°C/110°F, and the sand transmits the can be fitted into a sling. heat to pots and flats of plants and seeds Pot holders Simple metal rings attached to placed upon it. Soil-heating systems are fre­ brackets can be used to support pots. Fix the quently used with mist propagation. rings to greenhouse frame uprights. Alpine houses frequently have stagings topped with a tray containing 4-6 in of Permanent supports gravel, into which the pots containing the Plant support systems are discussed on page plants are plunged. Again, a strong per­ 50. Permanent supports, such as the system manent structure is essential. Alpines can of wires illustrated right, must be planned also be grown in bench-top beds. Often two when other fittings such as benches, staging beds are constructed: one filled with stony, and shelves are being considered. In a lean- acid soil, the other with a free-draining to house the rear wall can be wired for the alkaline soil. growing of espalier or cordon fruit trees or climbers. Walls should be scrubbed down, Shelves preferably with a fungicide, rendered if The use of narrow shelves above the main necessary and then painted or whitewashed bench or staging maximizes growing space before the wires are fitted. Trellising can be and allows pot plants to be placed where they fitted to battens and hinged at the bottom to pest and disease organisms. If the wall is Fix 2 in square wood battens vertically are attractive yet not in the way of propaga­ allow the wall behind to be painted. This is of brick, repoint and render if possible. at either end of the wall. Using straining tion and other bench-top activities. Shelves only necessary for very long-lived plants such Then whitewash or paint the wall to bolts at one end, stretch wires horizontally may be fixed to the glazing bars or suspended as vines. Full details can be found in Gardening provide a light-reflecting surface. between the posts, 15-18 in apart. from them. Shelves can also be suspended Techniques in this series. Propagating aids 1

All gardeners like to propagate their own humidity, temperature, gas content and light propagated successfully without protection able cost, they are much to be preferred to plants, at least by the two basic means of transmission; and the environment of the For these reasons a properly-constructed inexpertly-made or put together do-it-your­ sowing seeds and taking cuttings. The prin­ medium (soil or compost), which covers tem­ heated propagating frame or case is highly self frames. The cheaper custom-built cases ciples and methods of propagation are dealt perature, moisture, aeration and chemical desirable. In addition, the larger propagating have cable heating which maintains a tem­ with on pages 55-63, the equipment used, on reaction (acidity/alkalinity). The job of propa­ cases can be used to house a small collection perature around 65"F/18"C. If outside con­ the next two pages. gation equipment is to modify these factors of tropical plants in a cold or cool greenhouse. ditions are cold, however, the temperature Most tender plant seeds germinate more to provide the optimum conditions. can drop much lower and for this reason ,a readily if kept at a temperature a little warmer The ideal environment An ideal environ­ Propagating cases more efficient heating unit coupled with a than is required by the growing plant. Seeds ment is one that allows minimum water loss Basically, the propagating frame or case is a thermostat is desirable. If tropical plants are of hardy and half-hardy vegetables and from the plant, cool air temperatures, smaller version of a garden frame. It provides being propagated, it must be possible to flowers are often sown under glass in late adequate light penetration, a normal atmo­ a closed high-humidity environment and can maintain a minimum temperature of about winter or early spring before the weather is spheric balance between soil and air, good be used either in the greenhouse or indoors if 75°F/24°C. Sophisticated units have both warm enough outside. The main problem in drainage and warm soil temperatures. The light is adequate. The case can be of wood or bottom heat to warm the soil and cables propagation is to ensure survival of the acidity/alkalinity reaction should be neutral. aluminum, with a cover of glass or plastic around the sides to warm the air. propagated material (be it seed, cutting or The degree to which a particular system of sheeting. Bottom heat can be supplied elec­ Unheated propagators If most of the propa­ graft) until it forms a new young plant. If the environmental control operates will limit the trically by soil heating cables (see page 22) gation is done from late spring to late sum­ correct material has been used at the start, propagation techniques that can be used or custom-made units with built-in heating mer, bottom heat is not so important and a and properly prepared, then success is successfully within it. In general, the "softer" elements can be purchased. Small units are wide variety of custom-made propagators directly related to the control of the environ­ or less hardy the plant material the greater heated by light-bulbs fitted to the end walls, without heat are available. Like the heated ment by the gardener. will be the degree of environmental control or by fluorescent lighting tubes. For the ones, they are largely of plastic, the bottom Environmental factors In plant propagation needed to achieve success. The vagaries of amateur there is now a wide range of easily- being like a seed flat, the top an angular there are two environments: the aerial en­ the normal outdoor climate are too great portable propagating cases with a heating dome of clear rigid plastic. Home-made vironment, which can be broken down into for all but the easiest and hardiest plants to be unit as an integral part. Generally of reason­ frames of wood and glass or plastic sheeting

A mist unit provides fine sprays of water in trols the soil heat, and a cut-off switch, the air above the plants, which are thus responsive to light, moisture or time, the constantly covered by a fine film of water. water supply. Sunlight is uninterrupted as Such a unit is used in conjunction with there is no need for a glass or plastic cover. An ordinary seed flat, pan or pot can be Purpose-made propagators have a domed soil-heating cables. A thermostat con­ Mist units can cover entire benches. converted into a propagator if polyethylene plastic top over an ordinary seed flat. sheeting is spread over hoops and sealed. Ventilators are usually fitted. Propagating aids 2

CAN be just as effective and for small-scale way. As a result, a high level of photosynthesis will raise the temperature excessively , in Heated propagators propagation some of the rigid plastic boxes tan continue from the moment of insertion closed cases, sometimes to lethal limits. sold for food storage are useful. Simplest of and subsequent rooting is more rapid and Shading must then be provided for all propa­ all is a plastic bag with either the pot of assured. There can be weaning problems gators enclosed with glass or plastic. This can cuttings or seeds placed inside, or with the with some of the more difficult to root plants be done by shading the cases or frames bag inverted over the pot. If the latter method once they reach the potting stage. themselves or the glass of the greenhouse is used, two U-shaped loops of galvanized The system known as intermittent mist above. Any of the shading methods described wire can be pushed into the rooting medium is also useful. The spray nozzles are coupled on page 16 can be employed, though the to prevent the bag from collapsing onto the to a solenoid positioned among the cut­ permanent or semi-permanent liquid prep­ cuttings or seedlings. tings. When the solenoid dries sufficiently it arations are less desirable in climates where actuates a switch to start the misting again. long, dull spells can be experienced at any Mist units Another method is triggered by an absorbent time of the year. Ideally, shading should be For the gardener who is particularly keen to pad attached to a switch. When the pad is used only on bright days or during sunny propagate plants of all kinds, a mist unit will wet and heavy it presses down and turns the spells so that photosynthesis is not curtailed ensure a higher rate of rooting success and system off. When dry it rises and turns it on more than necessary. A position at the north give much interest and satisfaction. Mist again. Where the growing season is persist­ side or end of a greenhouse is best. propagation requires electricity and piped ently warm and sunny, misting nozzles may The mist propagation method requires water supplies. It keeps the foliage of the be left on, or just shut off at night. little or no shade in temperate zones, parti­ plant material moist with a fine mist-like cularly if the unit is sited at the north side or spray of water, thus eliminating the need for Siting a propagator end of the greenhouse. In areas of hotter light-reducing covers of plastic or glass. The Whatever propagation equipment is chosen summer sun, light shading during the middle Small propagating cases are heated by a sun's light and heat can fall onto the cuttings it must be sited with care in the greenhouse. part of the day may be necessary unless con­ light-bulb in a glass-covered case. Flats are with only the greenhouse roof glass in the Adequate light is essential but direct sunlight tinuous misting nozzles are used. placed on the glass.

Soil heating Thermostat Roof shape

Soil-heating cables or heated panels in the An adjustable thermostat allows the internal A sloped roof causes condensation to run A kerosene-heated propagator can be used base heat the growing medium in larger temperature to be maintained at the to the sides of the roof, avoiding harmful where there is no electricity. propagators. required level despite weather changes. drips onto plants. Introduction/Hygiene 1

Of all the branches of horticulture, growing Summer A routine for an imaginary summer Winter Much the same procedure is followed Hygiene under glass is the most specialized. Not only day could be as follows. Once the morning in winter, but if the weather is cold and tem­ Along with the right environment and routine is the constant maintenance of the plants sun is fully on the greenhouse, check the peratures do not rise, ventilation and damp­ care, a good level of hygiene must be main­ necessary, but the environment must be con­ temperature. If it is about five degrees above ing will not need to be carried out and water­ tained to ensure healthy, vigorous plants trolled to give acceptable growing conditions. the desired minimum temperature for the ing will be minimal. The need to keep the greenhouse and parti The ideal environment The basic aim should plants being grown, open the ventilators by While this sort of routine is ideal for the cularly the glass clean is often overlooked. II always be to create an ideal environment for half to two-thirds. If temperatures continue plants, it is not easily carried out by the is surprising how much dirt can settle firmly healthy growth, but perfection is seldom to climb, open up fully around mid-morning. gardener who may have to be away all day. onto a sheet of glass in the open, even in possible, and never possible if a mixed col­ Damp down, shade if required and check that Happily, it can be modified and compromises areas where air pollution is low. This consider lection of plants is grown, for plants have there are no dry plants (but leave the main made. Full ventilation and essential watering ably cuts down light intensity, the effects of differing needs. In theory at least, the fully watering operation until later). In early after­ can be carried out just before leaving in the which are particularly noticeable in winter. automated greenhouse can be programmed noon, go over the watering thoroughly and morning and the main watering and damping Plants which need good light, such as tomato, to provide the correct levels of heat, light, damp down again if conditions are hot. If it is down done on arriving home. Damping down lettuce and freesia, look thin and pale and humidity and ventilation whatever the con­ not particularly hot, damp down in late after­ during the day, while desirable for most lack substance. ditions in the outside world. But in practice noon. As soon as direct sunlight is off the plants, is not essential. Automatic watering Class should be washed thoroughly in this is rarely the case. Freak weather con­ greenhouse the blinds can be rolled up and and ventilation help to optimize conditions autumn, using a suitable non-toxic detergent ditions, a breakdown of equipment or a when the temperature drops back to about in greenhouses left unattended during the Where the glass overlaps, dirt accumulate- simple power failure can quickly upset the five degrees above minimum, shut down day. and algae flourish, forming a dark band. automated system. In the end, it is the skill the ventilators. During a warm spell the In the winter a daily check over in the Remove this dirt with a metal plant label of the gardener that counts. Automatic temperature may not drop so low even after morning or evening is enough. If automatic or a sliver of sheet metal. Class washing equipment can at best work to only fairly nightfall and the greenhouse can then be left ventilators and capillary watering are in­ should be carried out at intervals during wide tolerances and has the disadvantage of open day and night. Ail depends on the stalled, then a weekly check over should the winter, especially in areas of air pollution. providing the same levels of water, heat and minimum temperature being maintained. suffice in winter. At other times of the year it is usually not so on for all the plants in the greenhouse. It is most important to get to know the limita­ Cleaning the greenhouse tions of the individual greenhouse and the degrees of tolerance of the plants being grown. This knowledge goes to build up the intuitive skill which all good growers have, to know when to water and ventilate, when to damp down, shade or feed for the very best results. All this takes patience and practice and the beginner must be keen enough to spend time with his plants, noting what happens to them under different conditions. Record keeping There is much to be said for keeping a greenhouse diary or notebook. Record in it the daily maximum and minimum temperatures, when seeds are sown or cut­ tings taken, when plants are potted, fed, staked, and stopped. In addition, comments can be made from time to time on the vigor, appearance and health of the plants. Over the seasons, a valuable record of the prevailing conditions is built up.

The daily routine It is important to establish a regular daily routine when gardening under glass. To fail In late summer, scrub the framework of the In autumn, wash the glass thoroughly using At the same time, scrub surfaces such as to do so is likely to lead to the disappoint­ greenhouse to remove pest and disease a non-toxic detergent. Remove dirt and paths and walls to remove algae, using a ments of poor-quality plants and frequent organisms. First empty the greenhouse. Use algae from glass overlaps with an alloy dilute solution of a proprietary algicide. failure of seedlings and young plants. a dilute sterilizing agent. plant label. Introduction/Hygiene 2 so important and in summer the layer of of soil or chemicals around the insides of the PEST AND DISEASE CONTROL Apply fumigants in the evening, then leave grime can even he beneficial, acting as pots. Soak clay pots in water to ensure Good greenhouse hygiene, as outlined in the the greenhouse closed overnight. Seal any partial shading, cleanliness. Perhaps the chief cause of infec­ previous section, is an essential starting point leaks and close all ventilators before applica­ At least once a year the framework of the tion of soil-borne rots is the use of dirty in the avoidance of pests and diseases. How­ tion. To sterilize the greenhouse, empty it of greenhouse should be scrubbed to remove containers for propagation. It is of great im­ ever, problems will inevitably occur because plants and burn sulfur at the rate of 1 lb per pest and disease organisms such as the eggs portance to ensure that containers are clean. it is impossible to avoid introducing infected 1000 cu ft. The burning sulfur produces sul­ of red spider mite and spores of fungal In order to avoid cross-infection, always material into the greenhouse. The following fur dioxide gas, which is highly poisonous. diseases. To do the job properly the green­ remove containers and used soil from the pages detail pests and diseases met with in Leave the greenhouse as soon as the sulfur house should be empty so that a sterilizing greenhouse when not in use. Spent soil pro­ the greenhouse and prescribe remedies. On is ignited. agent, a chemical fluid, can be added to the vides ideal conditions for the multiplication this page methods of control are discussed. washing water. Late summer is a good time to of both damping off fungi and sciarid flies. Biological control wash the greenhouse, when all but the It is important to wipe tools clean after use Control methods In the open, many harmful pests are kept tenderest plants can be stood outside. to ensure they do not become a potential Because the greenhouse is a closed environ­ under control by predators such as birds or In a humid greenhouse a film of green algae source of infection. ment it is often easier than in the open other insects. In the closed greenhouse can form on all moist surfaces including walls It is futile to go to great lengths to sterilize garden to control pests and diseases. Some environment, such natural balances break and floors, and can become slippery. All such soil, or to go to the expense of buying sterile pests, such as snails, can be removed by hand, down, leading to pest problems. In an effort surfaces should be scrubbed, using one of the soil mixes, if they are left lying about open to but most greenhouse problems will have to to avoid over-use of chemicals, biologists proprietary algicides in the water. the elements. All mixtures and their com­ be dealt with by chemical means. Some bio­ have investigated the possibility of biological Hygiene should not stop at keeping the ponents should be kept bagged and covered logical control is possible for a few green­ control. This means introducing a predator to greenhouse clean. All used pots and seed to maintain their reliability. Do not attempt house pests (see below). Good growing prac­ attack concentrations of harmful pests. Some flats should be thoroughly washed and to re-use spent soil mixes, even if sterilized, tice is the first line of defence, for healthy predators have been found to be regularly scrubbed before re-use to minimize the as the chemical balances will be out of sturdy plants are less susceptible to disease effective and are available commercially. A spread of disease. Remove any "tide-marks" proportion. than sickly ones. predatory mite, Phytoseiulus persimilis, con­ Applying chemicals Choose a chemical trols greenhouse red spider mite. A ladybird, which will not harm the plants being grown, Cryptolaemus montrouzeri, can be used but which is effective against the problem against mealybugs; a parasitic wasp, Encarsia concerned. Remove any plants likely to be formosa, for greenhouse whitefly; and a harmed by the chemical, or cover them with bacterium, Bacillus thuringiensis, attacks plastic sheeting secured with string or elastic caterpillars. bands. Carefully follow the instructions given If biological control is used chemical means on the next page for the use of chemicals in must be ruled out until the predators have the greenhouse. When spraying, open all had a chance to work, which limits its applica­ ventilators and the door. Many pesticides are tion if more than one pest is found. Predators also available as dusts which are applied from are a cure rather than a prevention: they a puffer pack. Use dusts on flowers and on cannot work until their prey, the pest, is plants sensitive to moisture on foliage. present. The critical time to introduce preda­ Fumigation Chemicals can also be applied in tors is when the pest first appears. The preda­ smoke form, a process called fumigation. tor can then breed and build up a large First check carefully that none of the plants enough population to eradicate the pests. present will be damaged by the fumigant to Predators will only breed faster than the be used. The manufacturer's instructions will pests when the daytime temperature exceeds contain a list. Remove any such plants from 21°C/70°F and light intensity is good. the greenhouse. Fumigants are available as While biological control avoids chemical simple pyrotechnic smokes which resemble build-up on plants, a point especially to be slow-burning fireworks, or as solids which are borne in mind with food crops, it is a less vaporized on electric elements. Fumigants certain and more complicated method of should be applied at a measured rate depend­ pest control than the use of chemicals. The ing upon the cubic capacity of the green­ use of predators has to be carefully timed. After use, wash and scrub seed boxes and kept in a bin with a tight-fitting lid to avoid house. Measure the capacity by the formula This may involve investigating sources of pots to minimize the spread of disease. staleness and possible contamination. length x breadth x average height. Fumiga­ supply well before the trouble is likely to Store containers neatly and do not allow Remove spent soil from the greenhouse tion can be used against specific pests or as a arise and taking swift action once the pests debris to build up. Potting soil should be after use. general hygiene measure every six months. are noticed. Pests and diseases 1

Introduction SEEDLINGS This section is concerned with the various This section covers the period of plant growth pests, diseases and disorders that may affect between germination and the emergence of plants grown under glass. It is divided into true leaves. two parts: ornamental plants, and fruits and vegetables. Within each part, the possible Seedlings eaten troubles are listed by symptom, such as Slugs, woodlice and millipedes can destroy Leaves discolored or Stems galled. Under plants by eating the foliage before the seed­ each symptom the various causes that may lings have a chance to become established. produce it are described and control measures Slugs are the most destructive; woodlice and suggested. millipedes only become troublesome when The most important means of controlling thev are present in large numbers. Slug pests and diseases is by good cultural prac­ pellets containing metaldehyde give some tice. In particular, ensure that plants are not additional protection against woodlice and allowed to become pot-bound or suffer from millipedes. Scatter pellets along seed rows. malnutrition, that they are given sufficient water and light, and that the greenhouse has Seedlings collapsing the correct temperature and humidity for the Damping off is usually due to species of the plants. If any of these conditions is unsuitable, soil- and water-borne fungi Phytophthora the plants will not only be much more sus­ and Pythium. Seedlings of antirrhinum, sweet ceptible to attack by pests and diseases, they peas, lobelia, stock and zinnia are particularly may also be damaged by the condition itself susceptible to infection, and collapse at and develop recognizable symptoms. Such ground level. Prevent infection by sowing problems are known as physiological dis­ thinly, since the disease is encouraged by orders. They are discussed under the appro­ overcrowding, and by using sterilized soil or priate symptom. compost of a good tilth. Over-watering can Plant wilting caused by over- or under-watering or malnu­ Even if plants are given the correct growing also induce damping off, so water carefully Bacterial wilt (Xanthomonas begoniae) trition; prevent it by maintaining even growth conditions, pests and diseases will still occur with clean water. Give adequate light but causes wilting and spotting on leaves of through good cultural treatment. occasionally, and in this case it is often not too much heat. Check slight attacks by winter-flowering begonia hybrids derived advisable to use pesticides or fungicides. watering with captan or zineb after removing from B. socotrana and 6. dregei. Burn severely Leaves distorted Such chemicals are, however, potentially all dead seedlings. Captan or thiram seed diseased plants and do not propagate from Tarsonemid mites are a group of tiny dangerous and must be handled with care at dressings can help prevent damping off them. If they are only slightly diseased, cut creatures that infest the growing points of all times; failure to do so may harm the user disease. out affected parts and decrease the tempera­ certain greenhouse plants. The bulb scale or damage plants. It is particularly important ture and humidity of the greenhouse. This mite (Steneotarsonemus laticeps) lives in the that the manufacturer's instructions are read BULBOUS PLANTS will reduce the spread and severity of the neck of narcissus and hippeastrum bulbs. and followed, and that all chemicals are This section treats problems that are specific disease, but it will also delay flowering. It causes a distinctive sickle-shaped cur­ stored in a cool dark place away from food­ to plants having bulbs, corms, tubers or Disinfect the greenhouse after a severe vature of the leaves and a saw-toothed stuffs, if possible in a locked cupboard where rhizomes. attack of the disease. notching along the margins. The flower children and pets cannot reach them. Wear stems become stunted and distorted, again rubber gloves when diluting chemicals, and Plant stunted Leaves discolored with a saw-toothed scar along the edges of thoroughly wash the sprayer, gloves and any Non-rooting of hyacinth bulbs is a physio­ Leaf scorch (Stagonospora curtisii) causes the stem. The cyclamen mite (Tarsonemus other equipment after use. Always spray logical disorder, the precise cause of which brown blotches to appear on the leaves of pallidus) and broad mite (Polyphagotarson- from all sides of the plant to give an even is not known. The leaves do not develop at the hippeastrum (amaryllis), particularly at the emus latus) live inside the leaf and flower buds coverage and ensure that both upper and normal rate and the inflorescence remains leaf bases, and also on the flower stalks and of plants such as cyclamen, Hedera (ivy), lower leaf surfaces are covered. Finally, avoid stunted. The roots of an affected bulb are petals. The affected tissues usually rot begonia, impatiens, saintpaulia and Sin- using insecticides on plants that are in flower either lacking or poorly developed. This and become slimy. Cut out such tissues and ningia (gloxinia). Their feeding causes stems since the petals may be damaged. problem can be caused by the temperature burn them. Spray or dust affected plants with and leaves to become scarred and frequently Plants that have been severely attacked by being too high during storage or forcing, or sulfur or zineb. to be distorted into spoon-like shapes. The pests or diseases should not be left in the by forcing or lifting too early. Unfortunately Unsuitable cultural conditions can check the growing points may be killed and the flowers greenhouse since they can become a source it is not possible to detect in advance those growth of hippeastrums, causing red blotches are either distorted or fail to develop. There of infection for other plants. All such plants bulbs in which the non-rooting tendency has or streaks (or both) to appear on the leaves, are no controlling chemicals available to should, if possible, be burned. developed. flower stalks and bulbs. This trouble is usually amateur gardeners. Burn all infested plants. Pests and diseases 2

storage but when the corms are replanted these caterpillars eat holes in the foliage. the rot progresses rapidly. Destroy badly Control light infestations by searching for and infected plants and disinfect the greenhouse. squeezing the caterpillars' hiding places. Sterilize the soil where diseased plants have Otherwise spray the plants thoroughly with been growing in beds. Examine corms when a dilute solution of trichlorphon when signs removing them from store and cut out any of damage are seen. Other caterpillars that brown areas. Then steep them for two hours can be found on greenhouse plants include in a 2 per cent formalin solution before those of the angle shades moth (Phlogo- planting them out. phora meticulosa) and the silver-Y moth (Autographa gamma). These feed in the open Inflorescence loose on the foliage and flowers but may be Loose bud of hyacinth, in which the stem difficult to find since they are active mainly at below the flower bud fractures completely at night. Control these pests by hand-picking or an early stage of growth, is usually caused by by applying the above insecticides. storing bulbs at too low a temperature. Slugs (various species) can damage most Bulbs that have been moved from cold plants, especially during the early stages of storage into a very warm place are parti­ growth. They frequently leave a slime trail on cularly susceptible. Loose bud may also be the foliage, which distinguishes their damage caused by incorrect lifting or forcing. Unfortu­ from that caused by caterpillars. Control nately it is impossible to detect the tendency them by scattering slug pellets based on for loose bud in a consignment of bulbs. metaldehyde onto the soil surface around the plants. Buds withering Blindness of bulbous plants is usually caused Leaves discolored by the soil being too dry at a critical stage of Faulty root action may be caused by over- or Leaves, flowers and bulbs rotting Bulbs, corms or tubers rotting growth. Prevent this by making sure that the under-watering, malnutrition or poor pot­ Soft rot (Erwinia carotovora var carotovora) Basal rot may be caused by various fungi, compost never dries out. Less frequently it is ting. It results in irregular yellow or brown causes a soft, slimy, evil-smelling rot of the and affects mainly Lilium and Lachenalia. The caused by storing bulbs before planting in blotches on the leaves, or complete dis- leaves and bulbs of hyacinths. It often com­ roots and base of the bulb rot, resulting in conditions that are too hot and dry. Prevent mences in the inflorescences when florets stunting of the top growth and discoloration this either by potting up immediately on have withered through a physiological dis­ of the leaves. Discard badly affected bulbs. obtaining bulbs, or by storing them in the SOOTY MOLD order known as blindness; for details see In less severe cases cut out diseased roots proper conditions. The flower buds of affected Some sap-feeding insects such as aphids, right under Buds withering. If the rot has not and tissues, or scales in the case of lily bulbs. bulbs turn brown and wither at an early whiteflies, scales and mealybugs excrete a advanced too far it may be possible to save Then dip the bulbs in a solution of captan or stage. Such bulbs can be planted out in the sugary liquid known as honeydew. Since the bulbs for planting outside by cutting out benomyl before re-potting. Prevent such garden but will not flower for a year or two. these insects feed mainly on the under­ all infected tissue. Such bulbs planted out­ troubles by using only sterile compost and sides of leaves the honeydew drops down side will not flower for a year or two. clean pots. GENERAL PLANTS onto the upper surfaces of leaves grow­ Begonia tuber rot and cyclamen corm rot The pests and diseases mentioned in this ing below the actual infestation. Such Roots or tubers eaten usually occur as a result of frost damage dur­ section may, unless otherwise stated, affect leaves become sticky, and under damp Vine weevil grubs (Otiorhynchus sulcatus) are ing storage. The tissues become soft and any type of plant, including those with conditions various black, non-parasitic plump white maggots about 1/2 in long with have a sweetish smell. Prevent these rots by bulbs, corms, tubers, or rhizomes. fungi known as sooty mold rapidly de­ light brown heads. Plants grown from tubers ensuring that tubers and corms of the velop. They do not directly harm plants are particularly susceptible but many other respective plants are stored carefully in a Leaves eaten because they grow on the honeydew, plants may be attacked. Usually the first frost-proof place. Carnation tortrix caterpillars {Cacoecimor- although the amount of light and air symptom that is noticed is the plant wilting Arum corm rot {Erwinia carotovora var caro­ pha pronubana) feed on a very wide range of reaching the foliage is reduced. Remove and, when it is tipped out of its pot, most of tovora) can be serious wherever arums plants and can be found throughout the year sooty mold by wiping the leaves with a the roots are seen to have been destroyed. {Zantedeschia spp. and hybrids) are grown in heated greenhouses. The "caterpillars grow soft damp cloth. Good ventilation makes Such plants rarely recover. Badly affected under glass in large numbers. The plants up to 3/4 in long and are pale green with brown the atmosphere drier and thus less suitable plants should be destroyed, the soil thrown wither and collapse due to rotting of the heads. They fold over the edge of a leaf with for the growth of sooty mold, but the away and the pot sterilized. Some protection corms; these may develop extensive brown silken threads, or bind two leaves together, best cure is to identify and control the pest is given by adding chlorpyrifos granules or areas with rotting roots arising from them. and when small feed unnoticed by grazing that is producing the honeydew. naphthalene flakes when potting up. The corm lesions can lie dormant during away the inner surfaces of these leaves. Later Pests and diseases 3 coloration of the foliage, and premature leaf- Glasshouse thrips (Heliothrips haemor- fall. Prevent such troubles by careful potting rhoidalis) are thin yellow or dark brown up and correct cultural treatment for the insects about 1/10 in long that live mainly on type of compost being used. Applications of the upper surfaces of leaves and on flowers. foliar fertilizer should help overcome the They feed by sucking sap and cause a full troubles, but in severe cases it may be neces­ green or silvery discoloration of the foliage, sary to re-pot the affected plant. which is also marked by minute black spots Tip scorch of the leaves of plants such as caused by the thrips' excretions. Control this aspidistra, chlorophytum and sansevieria pest by spraying thoroughly with a pyre- may be caused by the air being too hot or throid compound, derris, malathion or a dry, or by faulty root action (see above). systemic insecticide. Affected plants should recover once the scorched leaves have been removed and the Leaves with corky patches correct cultural treatment given. In the case Oedema, or dropsy, is caused by the atmos­ of saintpaulia, anthurium and palms such as phere being too moist or the soil too wet. It kentia, it may be necessary to place the pot in shows as pale pimple-like outgrowths on the a larger container packed with damp moss or undersurfaces of the leaves and on the stems. peat in order to create a humid atmosphere. The outgrowths later burst and then become Sun scorch of leaves usually shows as pale brown and powdery or corky. The most sus­ brown blotches (often elliptical) across the ceptible plants are eucalyptus, ivy-leaved foliage. It is caused by the sun's rays on a hot pelargonium, peperomia and camellias— day passing either through glass onto moist the last mentioned develops large scabby foliage, or through a flaw in the glass which patches on the undersurfaces. Improve the acts as a lens to intensify the rays. Prevent cultural conditions by careful watering and scorch in greenhouses by careful ventilation by ventilating the greenhouse. Do not re­ to reduce humidity. move affected leaves since this will only make Leaf spots are caused by a variety of fungi. In matters worse. practically all cases they produce brown or Corky scab of cacti is caused either by a lack black spots on the leaves, but on some hosts of light and the humidity being too high, or control eelworms, and infested plants should Leaves with visible fungal growth the spots have a purple border or they may by over-exposure to sunlight. It occurs most be burned. However, it is possible to give Powdery mildews are common on chrysan­ have pinpoint-sized black dots scattered frequently on Epiphyllum and Opuntia and chrysanthemum stools a hot water treat­ themums, begonias and cinerarias, and occur over them. Remove affected leaves and spray shows as irregular rusty or corky spots which ment so that they will subsequently produce occasionally on other plants. The symptoms with mancozeb or zineb. If further trouble develop into sunken patches as the tissues cuttings free of eelworms. Wash the dormant are white powdery spots on the leaves and occurs the plants may be lacking in vigor due beneath die. Where the trouble is very un­ stools free of all soil and then plunge them sometimes the stems. Ventilate the green­ to faulty root action, in which case see above sightly propagate from the affected plant and in hot water at 46°C/115°F for five minutes- house well since the fungi are encouraged by and previous page. ensure that new plants are given correct it is important that the time and temperature a humid atmosphere. Plants that are dry at "Ring pattern" on saintpaulias and achimenes cultural treatment and are not exposed to are exact. Then plunge into cold water. the roots are more susceptible to infection, is caused by a sudden chilling of the leaves too much light. so water before the soil dries out completely. from watering overhead in sunlight. Affected Leaves mined Fumigate the greenhouse with dinocap leaves develop large yellow rings. Prevent Leaves blotched Chrysanthemum leaf miner grubs (Phyto- smokes or spray with dinocap or benomyl. this by careful watering. Chrysanthemum eelworm and fern eelworm myza syngenesiae) tunnel the leaves of Remove severely affected leaves. Viruses such as tomato spotted wilt and (Aphelenchoides ritzemabosi and A. iragariae) chrysanthemum and related plants such as Rusts can affect chrysanthemums, fuchsias, cucumber mosaic affect a wide range of are microscopic worm-like animals that live cineraria (Senecio cruentus hybrids) and ger- pelargoniums, cinerarias and carnations. On plants. In general the symptoms are mottled, inside leaves. Many different plants may be bera. These mines show on the leaves as fuchsias and cinerarias orange powdery blotched or striped leaves, affected parts infected, although in greenhouses the main whitish-brown lines meandering through the pustules develop on the leaves, predomi­ being pale green, yellow or black. The hosts are those indicated by the pests' com­ leaf and, in heavy infestations, leaves may nantly on the lower surfaces. On other plants leaves may also be distorted and the plants mon names. Infested parts of the leaves turn lose almost all their green color. A single the pustules produce masses of chocolate- stunted. Destroy any plant showing these brown. At first these areas are clearly separ­ application of benomyl pirimiphos-methyl colored spores. Remove arrd burn affected symptoms. A valuable plant such as an ated by the larger leaf veins from the green, controls this pest if applied as soon as mining leaves. If severely infected, destroy the plant. orchid may be kept but it will always produce healthy parts, but eventually the brown areas begins, but if the plants are badly infested Reduce the humidity of the atmosphere, and discolored leaves and the trouble may spread coalesce and the whole leaf dies. None of the three applications of insecticide at ten day avoid wetting the leaves. Spray at seven to to previously healthy plants. chemicals available to amateur gardeners intervals will be necessary. ten day intervals with zineb or mancozeb. Pests and diseases 4

Leaves with pests visible and the top growth wilts or collapses. Prevent the latter have yellow-brown, flat, oval shells yellow insects, about 1/10 in long, that suck Greenhouse whitefly (ltrialeurodes vapor-iro- these diseases by using sterilized soil mixes of the same length. The insects live under­ sap from the petals of carnation, chrysan­ rum is one of the most common and and pots, and by using clean water. Pot up neath these shells and feed on sap. Once themum, cyclamen and other plants. The troublesome of greenhouse pests. for details, carefully and tease out the roots of pot- a suitable feeding place is found they do not petals develop white flecks where the thrips sec page 40. bound plants. Control by watering with move. Control by spraying plants thoroughly have fed. Control them by spraying thorough­ Peach-potato aphid and mottled arum aphid ethazol plus benomyl, or use a solution of with malathion or nicotine three times at two ly with malathion or nicotine. Care needs to (Myzus persicae and Aulacorthum circum- Banrot as a soil drench. In severe cases re­ week intervals. be taken since flowers may be marked llexum) are both species of greenfly that suck pot, using a smaller pot if necessary, in sterile Mealybugs (Pseudococcus spp.) are gray- by insecticides, so spray when the plants sap from a wide range of plants. For details, soil or potting mixture after having removed white soft-bodied insects that grow up to 1/4 in are not exposed to bright sunlight or high see page 40. all dead parts including roots. Spray the long. They infest cacti, succulents and many temperatures. Soft scales (Coccus hesperidum) are sap- developing leaves with a foliar fertilizer. other plants, and secrete white, waxy fibers Viruses such as cucumber mosaic and feeding insects that live on the stems and Gray mold (Botrytis cinerea) causes plants to that cover the mealybug colonies and their tomato spotted wilt can cause spotting or undersides of leaves near the main veins. For decay and affected leaves and flowers to egg masses. Control them by spraying with streaking of flowers, which may also be dis­ a description of these pests and their control, become covered with a gray-brown mass of malathion or nicotine. Thorough applications torted. Most frequently affected are chrysan­ see below. fungal spores. The petals may also develop are necessary because mealybugs tend to themums and bulbous plants, especially numerous small red or brown spots. Cray live on relatively inaccessible parts of the lilies and cyclamen. Destroy affected plants. Leaves mottled mold spores are always present in the air plant, and two or more sprays at two week Greenhouse red spider mites (Tetranchus and infect plants through wounds and dead intervals may be needed. On plants that are Flowers spotted or rotting urticae) are minute pests that attack most or dying tissue. Infections can also occur liable to be damaged by insecticides, such as Gray mold (Botrytis cinerea) frequently attacks greenhouse plants. For details, see page 40. between diseased and healthy tissues. Pre­ Crassula and ferns, dab mealybugs with a the flowers of cyclamen and chrysan­ Greenhouse leafhoppers (Zygina pallidifrons) vent gray mold by good hygiene and by brush dipped in methylated spirit. themums. For symptoms and treatment, see suck sap from the undersides of leaves and removing dead leaves and flowers promptly. under Stems or crowns rotting, above. cause white, pinhead-sized dots to appear on Ventilate the greenhouse carefully to reduce Stems galled the upper surfaces. In heavy attacks these humidity, and water early in the morning and Leafy gall (Corynebacterium tascians) affects Pests in or on the soil dots coalesce and most of the leaves' green not at night. Once the disease has appeared mainly pelargoniums and chrysanthemums, Vine weevil grubs (Otiorhynchus sulcatus) color is lost. Adult leafhoppers are about on any type of plant, spray with benomyl or and shows as a mass of abortive and often are plump white legless grubs, up to 1/2 in long, 5/8 in long and pale yellow with two V-shaped a copper fungicide or use Isotherm Termil fasciated (flattened) shoots at soil level. with light brown heads. For symptoms of gray markings on their back. The nymphal bombs. In the case of cyclamen affected by Destroy affected plants and sterilize pots and attack, and treatment, see under Roots and stages are creamy-white. As they grow they gray mold around the crown, dust with the greenhouse bench on which the plants tubers eaten in the Bulbous plants section. periodically shed their skins, which remain captan. were standing. Do not propagate from dis­ Fungus gnats or sciarids (various species) are attached to the undersides of the leaves. Carnation wilt is caused by the fungi Verti- eased plants. For details of sterilizing, see small gray-black flies that run over the soil Control leafhoppers by spraying with any of cillium albo-atrum and Fusarium oxysporum page 33 on Hygiene. surface of pot plants or fly slowly around the insecticides malathion, pirimiphosmethyl, f dianthi. Affected plants wilt rapidly and the them. Their larvae are thin white maggots up methoxyclor or a pyrethroid compound. leaves become either yellow or gray-green Flower buds dropping to 1/4 in long with black heads. They live in the and then straw-colored. In both cases a Bud drop affects stephanotis, gardenias, soil and feed mainly on rotting plant material Stems or crowns rotting brown discoloration can be seen in the inner hibiscus and camellias. It is caused by the soil but they sometimes damage the roots of Blackleg (various organisms) affects pelar­ tissues of affected stems. Prevent these being too dry at the time the buds were seedlings and plants that are in poor health. gonium cuttings and sometimes the mature diseases by using sterilized pots and soil. beginning to develop. Prevent this trouble They may also tunnel into the base of soft plant. The stem bases become soft, black Destroy severely affected plants and sterilize by ensuring that the soil never dries out. cuttings and cause them to rot. Control the and rotten, and affected plants die. Prevent the greenhouse bench or floor on which the Gardenias may also lose their buds if the adult flies by spraying with a pyrethroid this disease by using sterile soil mixes and plants were standing. Do not propagate atmosphere is too dry. Prevent this by compound. Against the larvae, mix some pots, and by hygienic cultural conditions, from diseased plants. To reduce the spread syringing the plants in the morning and diazinon granules into the soil around the including the use of clean water. Destroy of wilt drench the remaining plants with a evening during warm sunny weather except plants. severely diseased cuttings, but in the case of solution of benomyl or thiophanate-methyl, when the flowers are open, otherwise they Springtails (various species) are white soil- valuable plants it may be possible to propa­ repeating the treatment two weeks later. will discolor. Over-watering can also cause dwelling insects, about 1/10 in long. They are gate by taking a fresh cutting from the top of bud drop of gardenias. Bud drop can be found especially in peat-based mixes, and a diseased plant. Stems or crowns with pests visible avoided by careful greenhouse management. are distinguished by their habit of jumping Foot, crown and root rot may be caused by Scale insects such as hemispherical scale Ensure that temperature, humidity and venti­ when exposed on the surface of the soil. They black root rot fungus or other soil or water- (Saissetia coffeae) and soft scale (Coccus lation are correct. usually appear on the soil surface after plants borne fungi. These organisms cause a brown hesperidum) encrust the stems of many have been watered. However, they cause no or black rot of the tissues at the base of the different plants. The former have red-brown Flowers discolored damage and there is, therefore, no need for stems, around the crowns or at the roots, convex shells about ^ in in diameter, while Thrips (various species) are thin, black or any controls. Pests and diseases 5

dirty tanks and butts. give adequate light but still produce good crops it the deficiency is not too much heat. Check slight attacks by corrected early on. HORMONE WEEDKILLER DAMAGE watering with captan or zineb after removal This commonly affects plants under glass, of the dead seedlings. Leaves moldy particularly vines and tomatoes. Affected Wirestem fungus, caused by Rhizoctonia Tomato leaf mold (Cladosporium lulvum) leaves become narrow and fan-shaped, solani, is a disease of brassica seedlings, affects only tomatoes grown under glass or show parallel veins, are frequently cupped particularly cauliflowers, but the same fungus polyethylene. A purple-brown mold develops and the shoots twist spirally. Take care can also affect seedlings of other vegetables. on the lower surface of leaves which show when using hormone weedkillers, apply Stems of affected brassica seedlings shrink yellow blotches on the upper surface. These ing them with equipment kept solely for at ground level before they topple, but other symptoms may be overlooked as affected their use. Do not use them on a windy day seedlings damp off as described above. Let­ leaves are subsequently often attacked by and, when spraying nearby, close green­ tuce seedlings affected by this fungus usually gray mold. Grow resistant varieties and keep house ventilators. Do not store weed­ succumb to gray mold (see below) fairly the greenhouse temperature less than 21°C/ killers in a greenhouse since vapors from soon afterwards so that the original cause 70°F. Ventilate well since the disease is them can affect plants. Wash hands and may be overlooked. Prevent by sowing encouraged by humid atmospheres. At the tools after applying weedkillers. thinly in a good tilth and avoid over-watering. first signs of trouble spray with benomyl or Use sterilized soil or a good-quality soilless mancozeb or use Exotherm Termil every Leaves discolored mix to help prevent infection. The fungus is 7 days. (see above). The top growth wilts or collapses Downy mildew of brassica seedlings, especi­ not controlled by fungicides with the excep­ completely because these soil: and water- ally cauliflowers, is caused by the fungus tion of dicloran. The chemical can be raked Leaves and stems rotting borne organisms attack the roots and stem Peronospora parasitica and that of lettuce by into the soil before sowing seed where this Gray mold (Botrytis cinerea) is a common bases. Prevent this by the use of clean water Bremia lactucae. White mealy or downy tufts disease is known to be troublesome. problem under glass, affecting particularly and by changing or sterilizing the soil at of fungal growth develop on the underside of grapes, strawberries, cucumbers and tom­ least once every three years, or by the use of the leaves, which become blotched on the DISEASES OF MATURE CROPS atoes. Lettuce tends to wilt due to attack at sterile soil. Plant carefully, and tease out upper surface. Affected seedlings are severely The diseases described below may affect any ground level. Affected stems, fruits and leaves roots of pot-bound plants. Do not over- or checked and lettuces may later be attacked crop, fruit or vegetable, being grown in rot and become covered with a gray-brown under-water as plants suffering from faulty by gray mold (see below). These mildews are greenhouses, cold or heated frames or under velvety fungus growth. Sometimes the fungus root action (see above) are very susceptible most troublesome on overcrowded seedlings cloches, unless otherwise stated. Vines and does not rot tomato fruits but produces pin­ to attack. If foot rot occurs, water with a growing in very humid conditions. Prevent peaches are treated separately at the end of point spots, each with a pale green ring, solution of captan, or alternatively, zineb, the diseases by sowing seed thinly in steril­ this section. known as water spots, which can still be seen or dust at the base of the plant with dry ized, well drained soil or seed sowing mix, and on ripe fruit. Spores of the fungus infect plants bordeaux powder. When tomatoes are ventilate carefully to reduce humidity. Do not Leaves discolored through wounds and dead and dying tissues, affected, place fresh sterilized soil around over-water seedlings. Should mildew occur, Faulty root action is due to over- or under- or by contact between diseased and healthy the base of the stems and spray all plants remove diseased leaves and spray with watering or poor transplanting and can cause tissues. Remove dead leaves and over-ripe with a foliar fertilizer to encourage the mancozeb or zineb. On brassica seedlings, irregular yellow or brown blotches on the fruits promptly to avoid infection. Ventilate development of new roots in the fresh soil. chlorothalonil and captafol may be used. leaves. Prevent this by careful planting and greenhouses carefully to reduce humidity As these new roots develop they should re­ correct cultural treatment. Applications of a and water early in the morning, not at night. vitalize the plants. Stems collapsing foliar fertilizer should help to overcome the Over-watering plants should be sprayed Verticillium wilt is caused by species of the Damping off is usually due to species of the trouble, but with severely affected tomatoes with thiram every three or four weeks. fungus Verticillium. The larger leaves wilt soil- and water-borne fungi Phytophthora it may be necessary to mound sterile soil Prevent infection of grapes and strawberries during the day, particularly on hot days, but and Pythium. Seedlings of lettuce, tomato, around the base of the stem into which new by spraying with benomyl as the first flowers recover at night. Affected plants may lose mustard and cress are most susceptible to roots can grow as the plant recovers. open, repeating twice at ten day to two week their older leaves. Brown streaks are seen infection, and collapse at ground level. Over­ Magnesium deficiency is common on tom­ intervals, or with captan or thiram except running lengthways in the tissues if the base crowding encourages the disease, therefore atoes and eggplants. Orange-yellow bands on fruit to be preserved or canned. Fumigate of the stem is cut longitudinally. Destroy sow thinly and use sterilized soil of a good develop between the veins on the lower an affected greenhouse with smokes if badly affected plants. Prevent the disease by tilth or a well-prepared sterilized sowing mix. leaves, which gradually turn brown as the possible. using sterilized soil or planting mix, and The organisms that cause damping off are symptoms spread progressively upwards. always plant verticillium and fusarium re­ often present in unsterilized soil, particularly Spray at the first signs of trouble with 1/2 lb Stems wilting sistant varieties. Seed catalogs indicate which if it is compacted causing poor aeration. magnesium sulfate in 21/2 gal of water, to Foot and root rot can be due to various fungi, varieties are resistant. Overwatering can also induce damping off. which is added a spreader. Spray repeatedly including Thielaviopsis basicola and species Tomato stem rot {Didymella lycopersici) Use clean water to prevent infection by every seven to ten days until the plants have of Fusarium, as well as those fungi which causes a sudden wilting of mature plants. water-borne organisms which build up in completely recovered. Affected plants can cause damping off and wirestem of seedlings A brown or black canker develops on the Pests and diseases 6

stem, usually at ground level, and small black Chats (small tomato fruits) may form on by adequate and early ventilation, by ensur­ VINES specks, which are the fruiting bodies of the plants which are dry at the root, but poor ing that plants have sufficient shade, and by The most serious disorder to affect vines fungus, can just be seen with the naked eye all pollination caused by cold nights and a dry correct feeding and watering. Crow tomato grown under glass is powdery mildew. over the diseased tissues. These produce atmosphere may also be responsible. Encour­ varieties resistant to greenback. Consult seed many spores which over-winter and act as a age pollination by syringing the foliage in the catalogs for lists of tomato varieties resistant Leaves, shoots and fruits with fungal growth source of infection the following season. It is morning and again during the day when the to greenback. Powdery mildew (Uncinula necatof) shows a essential, therefore, to burn all debris and to weather is hot. soft white floury coating of fungus spores on sterilize the greenhouse and equipment at the Dry set of tomatoes is also due to poor pol­ Bronzing of tomatoes is caused by tobacco the leaves, young shoots and fruits. Affected end of the season if this disease has occurred. lination. It is caused by the atmosphere being mosaic virus. Brown patches develop be­ berries drop if attacked early, but in later Destroy badly affected plants and spray the too hot and too dry. The fruits remain 1/8 in neath the surface, usually at the stalk end, attacks become hard, distorted and split, stem bases of the rest of the crop with beno- across and become dry and brown. Syringe and give a bronzed patchy appearance to the and are then affected by secondary fungi myl or captan. Less severely diseased plants the foliage as described for chats above. young fruit. When cut open the patches such as gray mold. Ventilate carefully since may be saved by cutting out affected tissues show as a ring of small dark spots beneath the disease is encouraged by humidity. and applying a paste of captan mixed with a Fruits discolored the skin. With severe infection depressed Avoid overcrowding the shoots and leaves little water, or by painting them with a solu­ Blossom end rot of tomatoes shows as a streaks which fail to ripen may radiate from and provide some heat if the greenhouse is tion of benomyl. circular and depressed brown or green-black the stalk end. The internal tissues of such cold. Avoid also dryness at the roots. At the patch on the skin at the blossom end of the fruits show large brown corky areas. Plants first sign of mildew spray or fumigate with Flowers dropping fruit (the end farthest away from the stalk). In bearing bronzed tomatoes would have shown dinocap, spray or dust with sulfur, or spray Tomato flower drop is almost always due to most cases it is due to a shortage of water at a other symptoms such as stunted growth with benomyl. Up to four applications may be dry conditions at the roots. The flowers may critical stage in the development of young or mottled foliage earlier in the season and needed. In winter, after removing the loose open, but break off from the stalk at the fruit. Prevent this by seeing that the soil is should have been destroyed when these bark, paint the vine stems with a solution of joint and fall to the ground. Prevent this never allowed to dry out completely. All the symptoms first appeared. sulfur made up as follows: mix equal parts trouble by adequate but careful watering. fruit on one truss may be affected but those of flowers of sulfur and soft soap to form developing later should be normal if the Fruits rotting lumps the size of golf balls. Put one lump into Fruits failing to develop normally plant has a good root system and is looked Gray mold (Botrytis cinerea) can attack a jam jar with a little water and stir well with Withering of young cucumbers starting at after carefully. various crops. For details, see page 38. the brush used to paint the stems. the blossom end is due to uneven growth Greenback and blotchy ripening of tomatoes resulting from irregular watering. Remove all show as hard green or yellow patches on the Fruits bitter Leaves discolored the fruits from an affected plant to rest it, and fruits. The former occurs on the shoulder of Bitter cucumbers can be due to an excess of Scorch is due to the sun's rays striking spray the foliage with foliar fertilizer if a poor the fruit and the latter on any part. Both may nitrogen in the soil or irregular growth. Avoid through glass onto moist tissues on a hot day. color. Later-developing fruits should be nor­ be encouraged by high temperatures and a excessive use of nitrogenous fertilizers, and It shows as large brown patches which soon mal once the plant regains its vigor, providing shortage of potash; greenback is also caused maintain even growth by watering carefully. dry out and become crisp. Prevent this by there is no root disease present. Prevent fur­ by exposure of the shoulder to strong sun­ Since pollination of the fruit can also result careful ventilation in order to reduce the ther trouble by watering cucumbers carefully light, and blotchy ripening may occur where in bitterness, grow varieties having mostly humidity, and carefully remove all the and regularly. nitrogen is deficient. Prevent these troubles female flowers. affected leaves. Pests and diseases 7

Magnesium deficiency shows as a yellow- When shanking occurs early in the season, orange discoloration between the veins, cut out the withered berries and spray the COMMON GREENHOUSE PESTS but in some varieties the blotches may be foliage with a foliar fertilizer. purple. Later the affected areas turn brown. Splitting of berries most commonly occurs as Spray with 1/2 lb of magnesium sulfate in 21/2 gal a result of powdery mildew (see above). of water plus a spreader such as soft soap However, it is sometimes due to irregular or a few drops of mild washing-up liquid. watering. Remove affected berries before Repeat applications once or twice at two- they are attacked by secondary organisms week intervals. such as gray mold, and water before the soil dries out. Leaves with small globules Scald is caused by the sun's rays striking Exudation of small round green or colorless through glass onto moist tissues on a hot droplets from the leaves is quite natural and day. Ventilate carefully to reduce the humid­ usually goes unnoticed. However, in the ity. Remove affected berries showing sunken spring the transparent globules may become discolored patches. very noticeable on the young foliage. The Oedema occurs when the roots of an affected symptoms are most obvious on plants grow­ plant take up more water than the leaves Greenhouse red spider mite (Tetranychus both types often occurring together on the ing in a very humid atmosphere and they can transpire and is due to extremely moist urticae) are tiny, eight-legged creatures same plant, while the latter is yellow-green indicate that the root action is vigorous and conditions in the soil, the atmosphere, or that can occur in large numbers on the with a dark horseshoe marking on its back. the plant is in good health. Nevertheless, both. It shows as small warts or pimples on undersides of leaves. They are just visible Both types of aphid excrete honeydew ventilate carefully to reduce the humidity the stalks and sometimes on the berries and to the naked eye but a hand lens is neces­ upon which, in humid conditions, sooty and prevent other troubles. even on the lower leaf surface. These out­ sary to see them clearly. Despite their molds may grow and cause the leaves growths may break open and then have a common name, these mites are yellow- and fruit to blacken (see page 35). As the Vine dying blister-like or white powdery appearance, or green" with black markings; they only aphids grow they shed their skins, which Honey fungus (Armillaria mellea) frequently they may become rusty-colored and show become orange-red in the autumn when become stuck on the leaf surface where kills indoor and outdoor vines. White fan- as brown scaly patches. Do not remove the they hibernate. Their sap feeding causes they are held by the sticky honeydew. shaped growths of fungus develop beneath affected parts as this will make matters worse. the upper surface of the leaves to become These skins are white and are sometimes the bark of the roots and the main stems at Maintain drier conditions both in the air and discolored by a fine mottling. In severe mistaken for whitefly or some other pest. and just above ground level. Dark brown soil; with correct cultural treatment the infestations leaves dry up and the plants Control aphids by applying pirimiphos- root-like structures known as rhizomorphs affected plant should eventually recover. become festooned with a silken webbing methyl or pyrethroid compounds. Use develop on the affected tissues, grow out produced by the mites. Maintaining a the last-mentioned if the crops are ready through the soil and spread the disease. Dig PEACHES damp atmosphere helps to check this pest for eating. out dead and dying plants together with as The following remarks on split stone also but treatment with insecticides such as Greenhouse whitefly (Thaleurodes vapor- many roots as possible. If the greenhouse is apply to nectarines. malathion or dimethoate will also be ariorum) is a major pest of greenhouse vacant, sterilize the soil with 2 per cent needed at seven day intervals until the plants. Both the small, white, moth-like formalin, or change the soil completely before Fruit failing to develop normally pest has been controlled. Take care when adults and their flat, oval, white-green, replanting. Sterilizing is a potentially danger­ Split stone shows as a cracking of the fruit at applying these chemicals to cucumbers scale-like larvae feed by sucking sap from ous process. Wear gloves, protective clothing the stalk end, forming a hole large enough for and melons as they may be damaged by the underside of leaves. Like aphids, adults and a mask. the entry of earwigs. The stone of such a fruit insecticides. Avoid this risk by spraying in and larvae excrete honeydew, which is split and the kernel is either rotting or the evening when temperatures are allows the growth of sooty mold. White­ Fruit failing to develop normally absent. Affected fruits are susceptible to cooler, and by making sure the plants are fly eggs and immature stages are not very Shanking is due to one or more unsuitable secondary rotting. This trouble can be due to not dry at the roots. As an alternative to susceptible to insecticides, making well cultural conditions. The stalks of the grapes the soil being too acid. Lime to bring the pH insecticides this pest can be controlled established infestations difficult to con­ shrivel gradually until completely girdled. up to 6.7-7.0. Poor pollination can also cause by introducing a predatory mite, Phyto- trol. Early treatment with pirimiphos- Odd berries or small groups of berries then split stone, therefore hand-pollinate flowers seiulus persimilis. methyl or a pyrethroid compound such as fail to color and develop naturally at the by passing cotton-wool or a soft camel hair pyrethrum will prevent damage occurring early ripening stage. The berries are watery brush from flower to flower. The commonest Peach-potato aphid and mottled arum if applied early. Spray heavy infestations and sour, black varieties turn red, white cause of this trouble, however, is an irregular aphid (Myzus persicae and Aulacorthum several times at three to four day inter­ varieties remain translucent. Ensure over- or water supply. Prevent this by watering in dry circumflexum) are both species of greenfly vals. Greenhouse whitefly can be con­ under-watering or stagnant soil are not re­ periods and mulching to conserve moisture. that suck sap from a wide range of plants. trolled by introducing a parasitic wasp, sponsible. Reduce the crop for a year or two In particular, ensure that the soil is never The former is either pink or yellow-green, Encarsia formosa. until the vine regains its vigor. allowed to dry out. Feeding and fertilizers

Plants require certain basic (hemic .lis in order general cultivation of most plants. Some plants such as cacti and alpines need very when a plant needs a nutrient boost, such as to grow. In nature these arc present, to a plants require larger proportions of one little. Feed plants when they are growing, just before it flowers. greater or lesser extent, in the soil, contri­ element, and fertilizers are available which not when they are dormant. Plants that are Solid feeds Fertilizers in solid form—granules buted by the base rock and by the growth provide higher concentrations of potassium suffering from over-watering, incorrect en­ or powder—can be added to soil mixes. and decay of plant and animal life. A balance for tomatoes, for example. Special formula­ vironmental conditions, pests or diseases will The John Innes formulae call for the addition between the nutrients available in a given tions are sold designed for carnations, chrys­ not be cured by feeding. Establish the cause of certain amounts of John Innes base environment and the plants that will grow anthemums and various fruits and vegetables. of the trouble and take steps to correct it. fertilizer, which is made up as a powder. Solid soon forms and is maintained. Gardening Fertilizers containing several elements are When the plant has recovered and is growing fertilizers can also be added in the form of conditions, under glass or outside, upset this called compound fertilizers, simple fertilizers normally it will benefit from feeding. Follow top dressings to plants which are kept balance. In the greenhouse, the plants are in a contain only one element. They are applied the feeding instructions given for individual permanently in pots. Solid feeds are also closed environment. The only nutrients avail­ when specific deficiencies are diagnosed, but crops and carefully adhere to the instruc­ added to soil beds. The larger amount of able are those in the soil and those supplied must be used with care in the greenhouse as tions on the fertilizer pack. When using rooting medium in a bed makes it possible for by the gardener. it is easy to build up large concentrations liquid feeds, dilute to the proportions in­ solid fertilizers in slow-release form to be used. An explanation of the nutrient needs of of elements in soil mixes, damaging the structed and do not use too strong a mixture. These fertilizers are specially formulated to plants and a list of the essential elements is plants. In addition to the three basic ele­ Liquid feeding Liquid feeds are watered onto release the elements they contain over a given on page 45. ments, many commercially available com­ the growing medium and taken up by the period. When using solid fertilizers around Properly formulated soil mixes contain pound fertilizers also contain trace elements roots of plants. Because nutrients have to be plants, take care not to scorch the foliage. nutrients needed for at least the initial stages needed for plant growth. dissolved before they can be taken up by the Apply the top dressing as close to the soil of plant growth. At some point, however, roots, application in liquid form speeds the surface as possible and water in immediately. these nutrients will become depleted and Using fertilizer process of absorption and allows the nu­ Foliar feeding Some liquid fertilizers—but more must be added in the form of fertilizer. While nutrients are necessary, too great a trients to reach the plant quickly. Nutrients not all—and some special compounds, can This process is called feeding. concentration can be harmful. Nutrient salts applied to the soil or a mix in a solid form be watered or sprayed onto the leaves of can build up in the soil mix and damage are dissolved by water applied as irrigation plants. Foliar applications are very effective Types of fertilizer roots. Plants must be ted at the rate they can and are then taken up by the roots. in controlling deficiency symptoms, parti­ Balanced fertilizers contain nitrogen, po­ take up food. Fast-growing crops such as Because liquid feeds are fast-acting, they cularly of magnesium and the minor elements, tassium and phosphorus. They are used for tomatoes need heavy feeding, slow-growing are applied at frequent intervals, especially as the elements are quickly absorbed.

Applying fertilizer Foliar feeding

1 Mix liquid or powdered fertilizer with 2 Apply the dilute fertilizer to the surface of 3 Apply top-dressings to beds, borders and Mix foliar fertilizers according to the water in the proportions given on the pad the soil or potting mix with a watering can. large containers in granule form. Sprinkle maker's instructions. Apply to the leaves of Do not make solutions stronger than the the granules onto the soil or potting mix the plant until run-off, using a watering can recommended rate. and rake or fork in. fitted with a fine rose. Soil and mixes 1

Plants growing under glass, whether in a con­ tions and may contain good reserves of tainer or in a bed in a greenhouse or frame, nutrients. The bed must be well drained and, ROOT SYSTEMS have access to lower levels of soil nutrients unless it was previously part of a fertile than do plants in open ground. Therefore soil garden, extra organic matter should be in beds needs to be enriched, and special added. Well-decayed manure, garden com­ soils or mixes are required for pots or con­ post, leal-mold, peat or other organics should tainers. An understanding of the nutrients be dug at a rate of one 2 gallon bucketful per necessary to plant growth is important in square yard, ideally some weeks before plant­ order to judge what needs to be added to ing. Spread balanced fertilizer over the bed basic soils and growing mixes to ensure just before planting. Apply at a rate of 3-4 oz health (see page 45). per square yard. If the top-soil was stripped Beds provide a larger root run than do from the area prior to the erection of the containers, and therefore need less enrich­ greenhouse, the existing sub-soil should be ment. But the soil in the bed must be in good removed from the border site to at least one condition and well drained and aerated. Also, spade depth. Replace it with good top-soil or soils in beds may become infested with build­ a mixture of loam and one of the organic ups of pests and diseases, especially if the matter sources mentioned above. same crop is grown year after year. Con­ sequently the soil must be changed, or Mixes sterilized, regularly if beds are used. Apart from natural soil beds, plants can be grown in special mixes or composts, or in Beds inert media to which are added nutrients in Plants growing in open ground have room Container-grown plants have their root Ground level beds or borders created from fluid form (see Hydroponics, page 49). The to expand their root system in order to systems confined and therefore nutrients the soil on which the greenhouse is placed root systems of plants growing in containers search out water and nutrients. must be added to the soil available. can provide the best possible rooting condi­ are confined to a very much smaller volume

Greenhouse beds Replacing soil

1 Improve a greenhouse or frame bed by 2 Just before planting, rake in a balanced 1 If good top-soil is lacking, remove 2 Add good top-soil or a mixture of loam digging in organics such as well decayed fertilizer at a rate of 3-4 oz per square yard. exposed sub-soil to at least one spade's and organics to bring the bed back to the manure or garden compost at a rate of depth. Deal with any drainage problems. original level. At intervals add organics and 2 gallons per square yard. general fertilizer to maintain soil fertility. Soil and mixes 2

of soil than they would normally occupy in a to grow a wide variety of plants well, soon STERILIZATION bed or border (see box). If ordinary garden became popular, and is still widely used. soil is used in containers, vigorous plants in Any good potting medium must be well Commercially, loam is pasteurized in particular rapidly use up the available aerated and free-draining, but moisture- specially constructed flat-bottomed bins nutrients. This can be corrected by the retentive. It must contain sufficient fertilizers or troughs injected with steam from application of extra minerals in the form of to supply all the needs of the plants for as long below. There are also electric sterilizers, solid or liquid fertilizers, but plants will be as possible. In addition, it should be free from small versions of which can be bought and more successful if they can be kept growing weed seeds, pests and disease organisms. used by amateurs who garden on a at a steady rate from the beginning. To this These can be present in the basic loam which moderate scale. Small quantities of soil end it is necessary to create a richer, well- is an ingredient of most mixes. The John can be pasteurized in the kitchen, using a balanced soil for container-grown plants. Innes formula demands that the loam be steamer saucepan. Pass the loam, which Compost formulae In the past, professional sterilized to destroy harmful organisms. Al­ should be almost dry, through a1/2 in mesh gardeners devised their own formulae for though the term "sterilized" is widely used sieve and place a 6 in layer in the steamer. container soil, using in varying proportions in connection with soil and mixes, the loam Bring 2 in of water to the boil in the sauce­ such basic ingredients as turfy loam, decayed is actually heat-pasteurized, because it is pan. Then put the lid on the steamer and manure and leaf-mold, plus various ferti­ not desirable to kill all life in the soil. allow the loam to heat up. A thermometer lizers. These potting media were known as Loam The key ingredient of the John Innes must be used throughout the operation (a composts, not to be confused with the de­ formula is loam, the subtly-blended soil com­ candy thermometer is suitable) and once cayed vegetable matter known as garden posed of clay, fine sand, humus and minerals the surface of the loam reaches 82°C/ compost. The American term mix or potting that is found under long-established valley 180°F it must be kept as steady as possible mix is now commonly used. The need for a pastures. To create the finest loam the top for 10 minutes. As soon as the 10 minutes reliable standardized mix became imperative 4-6 in layer of pasture turf is removed and are up the loam must be turned out to cool. for research purposes as horticulture de­ stacked in layers. Between each 10 in layer of Loam can be steamed in large amounts 1 Pass good-quality, dry, fibrous loam veloped. In the 1930s the John Innes Institute turf a 2 in layer of strawy manure is laid. The by passing steam from a boiler into a pile through a 1/2 in mesh sieve. Prepare sieved in England devised such a formula. It proved stack should not exceed 6 ft high and wide of soil covered with a tarpaulin. loam to form a 6 in layer in the steamer.

Making loam

1 Cut sods 4-6 in deep from good pasture. 2 Water the stack, which should be no 2 Place the loam in the steamer and bring Alternatively, use a purpose-made soil Stack them grass side down in a sheltered more than 6 ft high and wide, and cover the water in the lower portion to the boil. sterilizer, which heats water by means of position, adding a 2 in layer of strawy well with heavy-duty plastic sheeting. Leave Keep at 82°C/180°F for 10 minutes. an electric element. manure between each 10 in of sod. tor six months until the sods have rotted. Soil and mixes 3 and the sods must be moist or made so as Preparing mixes the work proceeds. Ideally, the stack should be made in an open shed to protect it from the rain. Alternatively, cover the top with heavy duty plastic sheeting. The stacked sods will turn into high quality loam in about six months. Suitable pasture turf is in short supply and some of the commercial potting mixes sold are made with inferior loam. Generally speaking, however, such com­ posts are still superior to garden soil and equal to other substitutes. Test a mix before purchase by handling a sample. A mix made with good loam will have a high fiber content. How to make soil mixes The first stage in making soil mixes to one of the John Innes formulae is to sterilize the loam (see page 43). The mix should be made up as soon as the loam cools. Ingredients must be mixed well to obtain an even and uniform end product. It is helpful to have a bushel or half-bushel box in which to measure the ingredients, as lime and fertilizers are normally added at a 1 Prepare a bushel box for measuring 2 Fill the box with the first of the ingredients 3 Spread the first of the ingredients on a bushel rate. A bushel is the amount that will ingredients. The box should measure 22 in to the 10 in level. Do not compact the hard, dry surface. fit into a box 22 in x 10 in x 10 in without by 10 in. Mark the 10 in depth on the inside. ingredients. compacting. Evenly layer the ingredients into a pile on a clean concrete floor. Sprinkle some of the lime and fertilizers onto each sand layer. When the heap is complete it will clearly show layers of the various ingredients as they are of varying colors. The whole should be well mixed with a clean shovel. John Innes formulae The basic potting mix formula is: 7 parts by bulk loam, 3 parts of coarse washed sand, and 2 parts of moist moss peat. To each bushel of this mixture add 4oz of John Innes base fertilizer and |oz of ground limestone. This is a No. 1 compost or mix. For a No. 2 mix add twice as much fertilizer, and for No. 3, three times as much. For lime-hating plants a neutral to acid loam should be used if possible and the limestone omitted. John Innes base fertilizer is rarely available commercially but can be made up as follows: 2 parts superphosphate, 2 parts blood meal and 1 part sulfate of potash. For the seed-sowing mix the proportions are: 2 parts loam, 1 part peat and 1 part sand, 4 Sprinkle lime and fertilizer, according to 5 Add further ingredients in layers, 6 When all the ingredients have been adding to each bushel 11/2oz of superphos­ the formula being followed, onto the pile. sprinkling lime and fertilizers between added, mix the resulting heap with a clean phate and 3/4 oz of ground limestone, which each layer. shovel until the mix is an even color. Soil and mixes 4

is omitted for lime-hating subjects. It is recom­ mental work has been carried out to find become top-heavy. To overcome this factor mended that, except for very fine or slow alternative growing media. The most success­ and to render dryish peat more readily wet- PREPARING SOILLESS MIXES germinating seeds, sowing is made direct ful substance of all has been peat, in both its table, it is an advantage to add a small Follow the bushel proportions listed on into John Innes potting compost No. I, thus sedge and sphagnum moss forms. Soil mixes percentage of coarse washed sand. the left, with a quarter-bushel box (81/2 x doing away with seed-sowing mixes. consisting purely of peat with mineral U.C. mixes A series of simple standardized 8 1/2 x 73/4 in) substituted if smaller quantities Although there is plenty of experimental nutrients added are now the most popular of peat and sand media has been devised at the are required. The necessary chemicals can evidence to show the benefits of properly all for the amateur market. Professional University of California. They are known as be applied one by one or in the form of sterilized loam, it must be clearly stated that opinion, however, favors the adding of at U.C. mixes. There are three variations: 3 parts ready-mixed compounds available com­ good plants can be grown without it. Weeds, least some loam to peat-based mixes. by bulk moss peat and 1 part sand; equal parts mercially. The nutrients can be added pests and diseases will occur and have to be Peat mixes All-peat mixes have the advan­ peat and sand and 3 parts sand to 1 of peat. as the mix is used to save prior mixing. dealt with, but everything else considered, tage of being comparatively sterile and of To this is added a special fertilizer. If a commercial compound is to be used, the risks are not high. Weeds are a problem being light and fairly clean to handle. They Soil mixes for special purposes Lime-hating ensure that it includes the necessary trace when seed sowing and it is advisable to use have proved remarkably successful for a wide plants such as azaleas must be grown in lime- elements as well as the basic nutrients. one of the non-loam mixes mentioned below. range of container-grown plants providing free mixes. These can be bought, or normal Slow-release forms of potassium and A particularly annoying possible result of they are used to makers' instructions. They John Innes formulae can be used with nitrogen can be added to soilless mixes using non-sterilized loam is the introduction must not be firmed when potting in the way the lime omitted. The formula for John Innes to provide for plant needs for three of earthworms. Their tunneling activities can loam-based mixes are and watering must acid compost, intended for acid-loving plants, months or longer, removing the need for slow down plant growth and render the be done with care. If the plant's rootball is: 2 parts loam, 1 peat, 1 sand, with 1 1/2-oz feeding. Trace elements can also be mix so well drained that most of the water becomes too dry and shrinks away from the calcium superphosphate and 3/4 oz flowers of applied in fritted slow-release form. Fritted applied runs straight through. Kill the worms sides of the pot, subsequent watering is less sulfur added per bushel. To give a mix for trace elements are released over a period by watering affected pots with solutions of effective even when wetting agents are used. plants which require sharp drainage, add of months. Mixes should be used as soon potassium permanganate. As much for this reason as any other, all-peat gravel or grit to the mixture. Plants which as slow-release fertilizers have been added, mixes are best used for quick-growing short- need large amounts of water may benefit or they will build up in the mix before Soilless mixes term plants which require regular watering. from the addition of charcoal, which helps plants are present, leading to levels pos­ Sources of good loam have been in short A disadvantage of peat is the lack of prevent souring of the saturated mix. Steri­ sibly damaging to plants. supply for many years and much experi­ weight a peat rootball has. Tall plants soon lized leafmold can be used in mixes.

SOIL NUTRIENTS Balanced feeding is the key to successful The functions of the various nutrient normally present in most plants. It is essen­ up from the water by the plant's roots and plant growth although plant groups vary mineral elements are summarized here. tial to those enzymes involved in the trans­ combines with carbon dioxide, absorbed widely in their requirements of each Nitrogen Essential for the formation of pro­ porting of phosphorus within the plant. from the atmosphere, to form a sugar nutrient. If a plant is to thrive, its soil must teins which in turn make up protoplasm, Deficiency shows as severe chlorosis of the compound which is the plant's food. contain both the major and minor mineral the life-stuff of plants, nitrogen encourages leaves. Iron In its mineral form iron enters into elements. The macro or major nutrients leafy growth and promotes rapid growth Calcium A major element but required in the making of chlorophyll and therefore is are nitrogen, phosphorus, potassium, in the spring and summer. Insufficient nitro­ very small amounts, calcium is important vital to all green plants. Deficiency shows magnesium, calcium, sulfur, carbon, gen results in a general suppression of for the movement of carbohydrates in the as yellow to whitish shoot tips which often hydrogen and oxygen. Of these, nitrogen, growth. plant and aids in the entry of phosphorus, turn brown and die back. phosphorus and potassium (abbreviated Phosphorus Phosphorus is a constituent of nitrogen and sulfur with which it combines. Manganese Manganese is a trace element to N, P and K) are required in large quanti­ protoplasm which plays a part in photo­ Deficiency is rare but can show as wilting of needed for the functioning of various ties. In addition to these nine mineral synthesis, the complex process by which shoots, leaves and flower stalks. enzymes and cell chloroplasts. Deficiency elements, plants also need minute plants use light energy to make their own Sulfur Sulfur takes part in the formation symptoms vary but usually show as amounts of the minor, or trace elements food. Deficiency shows as thin shoots and of protoplasm and proteins. Deficiency is very chlorosis. such as iron, manganese, boron, molyb­ narrow leaves. rare in well-prepared soil mixes but when Boron Deficiency of boron, a trace ele­ denum, zinc and copper. Potassium (Potash) Essential to the function­ it occurs symptoms are similar to those of ment mainly concerned with cell division, All balanced fertilizers contain nitrogen, ing of enzymes active in the formation of nitrogen. results in a crippling or death of developing phosphorus and potassium with some fibrous tissue, sugars and starches, potassium Carbon, hydrogen and oxygen These ele­ tissues. of the trace elements occurring as im­ makes plants more disease-resistant. De­ ments are available from water and the Molybdenum, copper and zinc All three purities. Some balanced fertilizers are ficiency shows as thin growth. atmosphere. Oxygen is absorbed from the are vitally important, in small quantities, compounded so as to include balanced Magnesium Magnesium is a constituent of atmosphere and helps to convert the plant's to the proper growth of the plant. They amounts of trace elements. chlorophyll, the important green matter food (sugar) into energy. Hydrogen is taken are often present in soil mixes. Growing systems 1

Greenhouse growing systems are basec tainers allows staging and high-level shelves lesser extent cucumbers and tomatoes, are either on open beds or some form of con­ to be installed to maximize the use of growing traditionally grown on ridges or mounds of STERILIZING BORDER SOIL tainer to restrict root run. The size, type and space, though the space below the staging is soil on benches. This system not only gives site of the greenhouse and the choice of to a large extent wasted. The decision must the plants more light than ground-level beds, plants to be grown will dictate the kind of depend upon the crops chosen. but also enables the rooting medium to be growing system used. Another factor is the maintained at a beneficially higher tempera­ manner in which the greenhouse is to be run. Open beds ture than is possible at ground level without Container, or restricted, systems lend them­ If the greenhouse is sited upon good soil, and soil heating cables. This is because air can selves more readily to automated watering that soil is free of pests, diseases and per­ circulate below the bench as well as above than do soil beds, for instance. If mist units or ennial weeds, open beds are the simplest the soil surface. soil-heating cables are to be installed, then growing system. Open beds must contain a Although open soil beds are the most a bench or staging system with containers or good-quality soil or mix. If the soil is in­ suitable growing system for such early crops raised soil beds will be needed. adequate, modify or replace it (see page 42). If as lettuce, they are not economic of room Containers are the best growing system if the site is wet and difficult to drain, a raised where ornamentals are concerned. Climbers a large number of different plants is to be bed is the best solution. Construct one 9-12 in and shrubs given a free root run make strong grown in a greenhouse, for they can be deep with the sides retained by boards or a growth, but often at the expense of blooms. moved and re-sited as the plants grow, thus brick or concrete wall. Fill the space above A further disadvantage of soil-level beds, freeing space for further propagation and the cultivated garden soil with good-quality particularly if tomatoes are to be the main plant raising. Soil beds, on the other hand, do top-soil up to the level of the top of the wall. crop, is the possible build-up of soil-borne very well if only one major crop is to be grown Beds may also be formed on stagings, but the pests and diseases. This is inevitable if the at any one time. If, for instance, tomatoes or stagings must be specially built to support the same crop is grown year after year. The only Empty the greenhouse and open ventila­ carnations grown for cut flowers are to be the weight. Bench beds have the advantage of remedy is replacement or sterilization of the tors. Then, wearing gloves, apply a for­ main crop, then soil beds are preferable. Soil- bringing small plants nearer to the light and soil. Removing all the affected soil to 1ft maldehyde solution (one part of 38-40 level beds do not make use of the vertical to a level which makes cultivation easier. depth and replacing it with fresh, or sterilizing per cent formalin to 49 parts water) at dimension of the greenhouse except when They are especially applicable to the growing it (see page 43), is a laborious task. There are 5 gal per square yard. Leave for 4 weeks. tall crops are being grown. The use of con­ of alpines (see page 88). Melons, and to a methods of sterilizing the soil in situ with

Raised bed Bench bed Ring culture

On wet sites, raise the soil by building a Beds can be placed on benches at waist Ring culture consists of a bed of aggregate, containing soil. Roots penetrate into the 9-12 in deep raised bed. Use boards, a level. The benches must have extra-strong placed in a trough or a plastic-lined trench, inert aggregate, where they absorb moisture brick wall or concrete as sides. supports and drainage must be adequate. with plants grown in bottomless pots or rings and nutrients. Growing systems 2

steam or chemicals, but in the main they are in open soil without restricting the plants' feeding has to be begun early in the plant's as it is easy to over-water a large volume of not convenient for the amateur. The easiest roots to the confines of a pot. Each plant is growth. Proprietary liquid fertilizer, or a mix­ all peat mix. The mix also dries out quickly technique is to soak the soil with formalde­ grown in a bottomless pot stood on a bed, ture consisting of 2 parts nitrate of potash, and it can be hard to re-wet. Feeding is hyde (see page 46). The greenhouse must be or substrate, of gravel about 6-9 in deep. 3 parts sulfate of ammonia and 5 parts necessary to supplement nutrients. empty when this is done, and the soil cannot The substrate is laid in a trough lined with super-phosphate (all by weight) should be This method can be used for a wide range be used for at least one month after treat­ plastic sheeting to prevent it coming into applied to each ring weekly. Apply at the of plants but is particularly useful for toma­ ment. Formalin will give fair control of fungal contact with the soil. Thus the roots are able rate of 1 oz of the mixture to 1 gal of water. toes, peppers and small squash. It keeps plant diseases but has no effect on eelworms. to pass out of the bottomless pot and enter The main disadvantage of the ring culture roots away from the possible contamination Cresylic acid, D-D and methyl bromide are the substrate. Water is applied to the sub­ method is the need for precision in the of diseased soil in greenhouse beds. Growing used commercially against eelworms, the strate only, not to the pots, as soon as roots application of water and fertilizer. Water bags can also be used in concrete-floored latter controlling fungi also, but these chemi­ begin to penetrate the substrate. Dig out a loss can be high, especially early on when the greenhouses as temporary beds, and smaller, cals should never be used by amateurs. The trench in the border soil at least 6 in deep and roots have not yet penetrated the substrate. lighter growing bags can be placed on the work can be done by skilled contractors, but 16 in wide. Line the base and sides of the Ring culture means devoting the whole staging. Supporting tall plants such as toma­ it is costly and only worthwhile on a large trench with heavy gauge plastic sheeting and greenhouse, or a large part of it, to tomatoes. toes is not very easy. The traditional cane scale where other growing systems cannot fill it with the substrate. For the substrate Pot plants such as chrysanthemums can be stake cannot be used, for it will not sup­ be used. a mixture of three parts gravel to one of ver- stood on the substrate later in the year. port itself in the growing bag. It is necessary to miculite is recommended. Other suitable Plastic growing bags Crowing bags provide fix strings or wires to the greenhouse frame Restricted growing systems substrata are formed from perlite, stone restricted root runs but a larger than average above the plants and to train the plants. This term is used to describe growing systems chips or coarse sand. The substrate must be amount of growing medium. They are plastic The advantages of growing bags are free­ where the plants' roots are in some way chemically inert. sacks usually the size of pillows, filled with dom from disease, a growing medium that restricted by a container. Place fiber rings or bottomless pots at least an all-peat growing medium. They are laid warms up fast, and convenience. Against Ring culture The ring culture system was de­ 8 in deep on the substrate and fill them with a flat in the growing position and sections of these advantages must be set the difficulties vised for, and is mainly used for, growing sterilized rooting medium such as John Innes the top cut away so that plants can be in­ of accurately assessing feeding and watering tomatoes (see illustration, page 46). The aim potting compost No. 2 or 3. Soil-less media serted. Drainage is provided if necessary by needs, and the possible build-up of mineral of the ring culture system is to eliminate the can also be used. Because of the small amount making slits along the edges near ground salts in the peat. Crowing bags can also only problems of the build-up of pests and diseases of growing medium contained with the ring, level. Watering must be carried out with care be used once.

Growing bags

1 Place the bag on a flat surface in the 2 Add water to wet the peat-based 3 Water and feed the growing plants with needed. Feeding will be necessary as the growing position. Slit the top to provide growing medium. care, for it is easy to over-wet the peat in plants grow, although the peat in the bags planting spaces. the bag. Make drainage slits in the sides if has some nutrients added to it. Growing systems 3

Straw bales The growing of plants under glass sium nitrate and 3oz of ferrous sulfate, all The straw bale system on slowly decomposing bales of wheat straw rates per bale. Water the nutrients in. The can be considered a modern development of second method is that favored by com­ the old hot bed system. The reason for its mercial growers of tomatoes. development, however, is quite different. Its Fermentation Whichever regime is applied, aim is that of ring culture, to provide a disease- the straw will heat up through fermentaion free root run, primarily for tomatoes and and should reach 43o-54°C/110o-130°F. cucumbers. It is thus a restricted system, Check the temperature with a soil thermo­ although containers are not used. The straw meter every few days. When it drops to bales are thoroughly wetted and fermentation about 38°C/100°F and is still falling, planting is triggered by applying nitrogen, thus build­ can take place. ing up heat and giving off carbon dioxide. To plant, pile a ridge of John Innes No. 3 Both are beneficial to the young plants, which compost or equivalent mix along the top of are placed in soil mounds on the bales as the the bales and set the plants into this. Sub­ temperature in the bales starts to fall. The sequent watering and liquid feeding must be temperature in the center of the bale will, carried out regularly and thoroughly as the under the right conditions, reach at least bales are very free-draining. Plants should be 43°C/110°F. Due to the difficulty in obtaining supported with strings tied to the greenhouse straw and the relatively intensive care needed, roof (see page 50). Do not make the strings the system is a difficult one for the amateur. It too tight as the bales will settle. also restricts the use of the greenhouse as Straw bale culture has the advantage of the ammonia given off during fermentation providing heat and carbon dioxide which aid can damage some plants. plant establishment, but bales take up a lot The straw bale system is used for toma­ placed on fermenting wheat straw bales, Preparation Wheat straw bales are usually of greenhouse space. Care must be taken not toes, cucumbers and other food crops. into which the roots penetrate. Do not use used as they do not decompose quickly; to use straw sprayed with hormone weedkiller. Plants are grown in ridges of soil mix. straw sprayed with hormone weedkiller. barley and oat straw are inferior substitutes. Bales of 40-60 lb weight should be used. If Preparing the bales possible, they should be bound with wire rather than string, which can rot. They are put on polyethylene sheet end to end in rows where the plants are to be grown. The bales can be placed in a shallow trough lined with polyethylene, which helps to save water which runs through the bale. The ventilators should be kept closed, and the greenhouse temperature should ideally be around 10°C/ 50°F to promote fermentation. There are two alternative methods, one fast, one slow. Choose that which fits the period during which the greenhouse is free of other crops. The slower method first involves thoroughly watering the bales. Then water in 1 1/2 lb nitro-chalk (ammonium nitrate-lime mix­ ture) per bale. Four days later, apply a further 1lb of nitro-chalk, again watering in. Four days after that, add 3/4 lb of a general fertilizer and water in. Keep the bales damp at all times. This method takes about 18 days. The second method takes 7-10 days. Thoroughly wet the bales and then apply 1 lb 1 Add fertilizers as listed in the text to the 2 Check the temperature every few days 3 Sprinkle soil or mix in a ridge along the of nitro-chalk, 6oz of triple superphosphate, tops of the wet bales. Water the fertilizers during fermentation. Plant when it drops tops of the bales and plant. The roots will 6oz of magnesium sulfate, 12 oz of potas­ in. to 38°C/100°F. enter the straw. Growing systems 4

HYDROPONICS Nutrient film technique to the gardener. However, some details of Hydroponics systems Hydroponics is the technique of growing The nutrient film technique is a system of them are given so that the basic technique plants in water and dissolved mineral nutrients growing plants in troughs of shallow re­ may be understood. without soil or other solid rooting medium. circulating nutrient solution. Polyethylene Pure solution This method uses nutrients I he fluid used has to contain all the nutrients troughs or pre-formed open gullies are laid contained in tanks about 8 in deep with fine necessary to plant growth, and some kind of on flat surfaces in the greenhouse to a slope wire mesh stretched across the top to hold support system is necessary to replace the of not less than 1 in 100. A narrow strip of the stems of the plants upright. The nutrient anchoring action of roots in soil. non-toxic capillary matting is laid along the solution needs to be artificially aerated and The use of a hydroponic system does take base of the gully beneath each plant con­ regularly tested for pH, and must be changed away the skilled chore of watering and virtu­ tainer. This ensures that no plant dries out in every two weeks. Among the disadvantages ally eliminates diseases and pests of the root the early stages of growth and it leaves most of the pure solution method are the difficulty system. However, for success regular chemi­ of the roots uncovered allowing good, in­ of supporting plants adequately, and the fact cal analysis of the nutrient is essential. There expensive aeration. The nutrient solution, that only a limited range of species will are several nutrient formulae which the containing a complete range of plant foods, tolerate the permanent immersion of roots. amateur can try, some being available pre­ and if possible warmed to 25°C/77°F, is con­ Flooded substrate Similar tanks to those used mixed. If mixing is necessary, great care must tinually circulated by a submersible pump for the pure solution method are required for The pure solution system uses tanks of be taken. An excess or a deficiency of any through the troughs to a catchment tank at this system, but they must be protected with solution, with plant stems supported by one or more minerals could spell disaster to a flow rate of about 31/2 pints per minute per a layer of bituminous paint. Plastic-lined tanks horizontal wire mesh. the plants. None of the commercial systems gully. The systems available in kit form for or troughs are an alternative. The tank or now available can be recommended to amateurs are based upon modifications of trough is filled with an inert aggregate, ideally amateurs except to those interested in ex­ this technique. washed gravel or grit, though coarse vermi- perimenting for its own sake. Experiments culite, perlite, polystyrene chips, lignite or continue and a system wholly suitable for Other hydroponics systems weathered coal ash may also be used. This amateurs may be developed. Meanwhile, kit The other systems developed for commercial substrate is regularly flooded with the nutrient systems may interest enthusiasts. horticulture are of mostly academic interest solution, the surplus being recycled. The solution must be tested regularly for con­ Nutrient film technique centration and pH, and adjustments or replacement made when necessary. Replace­ ment of the solution is more costly than adjustment, but is more reliable, as the correct concentration is assured. The flood­ ing and draining operation ensures that sufficient air gets to the roots and the sub­ The flooded substrate system uses troughs strate gives the plants adequate support. filled with an inert aggregate which supports Drainage tank The drainage tank system is the roots. a simplified version of the flooded substrate method. The system can be adapted to a variety of situations. Dig a trench and line it as described under Ring Culture (page 46). Make drainage holes in the sides about 3 in above the base. Alternatively, any tank of similar depth and width with the same pat­ tern of drainage holes can be used. Ideally, use an absorbent substrate, such as vermi- culite, perlite or lignite, the last being recom­ mended. Washed sand that is not too coarse and thus has good capillarity is also suitable. Add nutrient solution to the substrate regu­ larly, the surplus draining away, a reservoir remaining below the drainage holes. Less The drainage tank system is similar to the The warmed nutrient solution is pumped matting and are covered by "tents" of nutrient is needed than for other methods, above. A trench lined with perforated from a storage tank along gently sloping black polyethylene to reduce evaporation. and checks are less frequent. gullies. The gullies contain a strip of capillary Amateur systems are smaller. plastic sheet is used. Plant supports

Many greenhouse plants require some kind cause for instance pots or growing bags are attached. Wires should be kept taut by the can be used in wooden-framed houses. of support to control and direct their growth. being used, drop lengths of strong string from use of a straining bolt at one end of the wire. Supporting plants in growing bags It is not Examples are tomatoes, fruit trees and orna­ secure fixings in the greenhouse roof to the Fix wires for fruit trees 15-18 in apart. Crapes possible to drive supports into the growing mental climbers. The plants that require sup­ base of each plant. Attach the string loosely need wires at a 10 in spacing. bag, as the small amount of soil will not port outdoors, such as certain shrubs and around the plant beneath the lowest true Wires can be used vertically to support hold a stake or cane and the plants which annuals, will also need support under glass, leaf. Twist the string gently around the plant climbing crops such as beans and ornamental grow up it. Self-supporting metal frames can though the supports need not be as strong as as it grows. Do not allow the string to become climbers. In all cases, attach the plants to the be obtained which stand over the bag. those used in the open. Permanent systems too tight. wires with soft string as necessary. Some Alternatively, drop strings from the green­ are needed for some plants such as grape Netting Plastic or plastic-covered wire net­ forms of plastic netting are perishable and house framework to the plants or attach vines. Such supports are attached to the ting can be draped from the greenhouse rot after a season or two. Do not use such plants to wall wires or nets. framework of the greenhouse, by nails or structure along the line of the plants. Support netting for perennial plants. Rigid wire or Supporting plants in pots Lightweight wire screws in the case of wooden frames, or by top and ends of the net securely to the frame­ plastic-covered wire netting can be fixed, frameworks can be bought which are inserted clips or bolts to metal frames. Other crops work. Gently guide the plants through the using battens, to walls or greenhouse frames into the potting mix. Several light canes such as tomatoes require temporary props. netting as they grow, tying in with soft string to provide support for climbing plants. tied together in a fan-shape achieve the same These are similar to those used outdoors, but as necessary. Netting of varying mesh sizes Fastenings Metal-framed greenhouses need result. Bushy twigs, as used outdoors for peas, use is often made of the greenhouse frame­ can be used. Some crops, such as melons and drilling, or the addition of special bolts, be­ are useful for supporting small climbers and work to anchor them. cucumbers, require large-mesh nets. fore wire or other support systems are other ornamental plants. If flowering plants Canes Bamboo or wooden canes can be Wires Fruit trees and climbers can be trained erected. Special bolts are available with T- such as carnations are being grown for used in borders where there is sufficient soil up permanent or temporary systems of wires shaped ends which slot into the glazing bars cutting in large numbers, plastic or wire to anchor them securely. Use one cane per stretched horizontally along greenhouse of most aluminum greenhouses. To these netting can be stretched horizontally above plant, of a height suitable for the mature walls. In lean-to greenhouses, screw eyes can bolts attach drilled brackets between which the bed or staging and the plants allowed to plants. Insert them on planting. Tie the plants be attached to rear walls and 14 gauge gal­ the wires can be fixed. Wooden battens can grow through it. to the canes with soft garden string at 12 in vanized wire fixed between them. Alterna­ be attached to the bolts to provide easy Perennials Fruit trees and climbers need intervals. tively, fix vertical battens to the wall and drill permanent or temporary fixing points for robust support systems to control and direct Strings Where canes are impracticable, be­ them for bolts, to which the wires are strings, nets or wires. Ordinary screws or bolts their growth. Avoid perishable materials.

Canes Strings Netting Tall crops Grape vines Lean-to walls

Tie the plants to bamboo Loosely tie strings below the Wire or string netting Tall or heavy crops need Vines require a rigid system Climbers can be trained up canes at 6-12 in intervals, plant's first true leaf, wind attached to the greenhouse stronger strings or wires of horizontal wires at 10 in a framework of wire mesh using soft garden string. them around the stems and frame can be used to and strong fixings to avoid spacings, firmly attached to fixed to battens. then run them to the frame. support plants. collapse. the greenhouse frame. Pots and potting 1

Until the advent of methods such as ring mainly because they did not have the porous Drainage All pots should have adequate 5-6 in. Pots are normally about as deep as culture and growing bags, most greenhouse quality of clay. However, as clay pots become drainage holes in the base. Lack of drainage they are wide, but half pots—half as deep as plants were grown in containers. There were more and more expensive, and often difficult leads to saturated soil and rotting roots. their width—are also used. They are often primarily a range of plastic or clay flower pots, to obtain, the controversy fades into the Good drainage also allows capillary watering called alpine pots as one of their main uses is with tubs being used for larger, semi­ background. It has been widely proved that systems to be used efficiently. The drainage for alpines and other low-growing plants. permanent plants. Containers are still the plastic pots will grow plants just as well as holes allow water to rise up into the soil Half pots can also be used for raising seed main tool for propagation, and they find clay, and it had become clear that they have from the capillary medium below. Many and for other propagation work when only a favor with gardeners who want to concen­ certain advantages. The first advantage is that plastic pots have a raised rim around the small quantity of material is being raised. The trate on ornamental greenhouse plants. They plastic pots are much cheaper than clay. They base. This lifts the drainage holes clear of the broader the base of the pot, the more stable provide the most versatile way of growing a are also more durable and easier to clean, for bench or shelf on which the pot is standing, it will be when it contains a possibly top- wide range of plants in a small greenhouse. they do not harbor dirt. Clay pots need allowing water to drain away through gaps heavy plant. Pots come in a wide range of sizes, and tubs soaking, scrubbing and sterilizing between in the rim. Without such a rim, water can be extend the size range upwards. There are also use, whereas plastic pots can be wiped clean prevented from draining away. Alternatives to pots several types of disposable pot, including with water and detergent. Plastic pots are Size and shape Pots are traditionally round, The illustration below left shows the range of those formed from organic material which also lighter than clay, which makes for easier and round pots have advantages in display­ alternatives to the traditional pot that is avail­ can be planted with the plant. handling. However, because they are lighter, ing plants. They are also easier to fill with able. Clay pots (a) have been joined by plastic Whatever container is used, there are plastic pots when used with light soilless soil, especially in the smaller sizes, than pots (b), also available as half pots (c). Shallow certain principles which must be followed mixes may be top-heavy. rectangular pots. Square pots do have the seed pans (d) are useful for sowing in small when potting, re-potting and potting on Plants in plastic pots need watering less merit of being economical on space. More amounts. Non-rigid pots such as black plastic plants. These operations are covered in frequently than those in clay, because clay can be fitted onto a shelf or into a propagating sleeve containers (e) are often used for trans­ detail on pages 52-54. pots are porous. The difference is minimal case. They contain a greater volume of soil planting and for plants for sale. Disposable Clay and plastic pots It was once asserted when plants are well rooted and growing than round pots of the same diameter. pots include peat rectangles (f), individual that only clay pots could be used to grow vigorously. Plants in plastic pots therefore Pots are measured by their diameter at the peat pots (g), paper pots (h), peat pellets (i) plants successfully. Plastic pots, when first need less day-to-day care than those in clay, rim in inches. Two sizes should be acquired and soil blocks (j). Flats in wood and plastic introduced, were viewed with suspicion, but there is a danger of overwatering. as the basis of a stock of pots: 2-21/2 in and complete the range (k and I).

Potting bench Soil blocking CONTAINERS

A potting table or bench with sides and a Moisten special peat-based blocking back keeps soil mix away from growing mix and press the blocking machine into areas. it. Use the blocks 24 hours later. Pots and potting 2

Disposable pots Peat pots and soil blocks Peat pots can be the plunger a little to consolidate the soil even when filled with damp soil mix. Make Several alternative systems have been de­ bought individually or in strips and blocks. mix. Place the soil blocks on a flat so that sure also that the seed flats chosen are of veloped to avoid the problems of root dis­ While they have the advantages in cutting they are touching and leave for 24 hours to good quality plastic: some sorts become turbance that result from growing in pots or the amount of root disturbance described consolidate. Then insert the seed or seedling. brittle when exposed to sunlight for any flats. Seedlings grown in flats, for instance, above, they are relatively expensive. They Pot on or plant out when the roots begin to length of time. are traditionally pricked out into small pots, are useful for sowing large seeds such as emerge from the sides of the block. Keep the One advantage of wooden flats is that a then moved again into individual pots or into beans. Soil blocks also involve expense, for a block moist at all times as the peat-based side or end can be easily prized away to allow the open garden. Sowing in soil blocks or peat special machine must be bought. However, blocking mix is difficult to re-wet. seedlings to be slid out in a block. If wooden pots makes these moves unnecessary. The the cost of the blocking machine can be set Substitutes for pots Plastic dairy produce flats are used, they must be carefully (leaned block or pot is planted with the young plant, against the saving in pots, whether of plastic containers, paper or plastic cups and similar between use. Without careful maintenance and provides it with extra humus as it is or peat, that soil blocks bring. Special soil substitutes can be used in place of pots when they rot easily and thus have a shorter lift' becoming established in its new pot or bed. mix is needed, but soil mix or its ingredients expense is a major consideration. Punch than plastic flats. Paper and papier mache pots have the same has to be purchased anyway, and its cost is adequate drainage holes in the base of the Substitute flats may be created by press­ effect. Bedding plants are often raised from the only factor once the machine is paid for. pots, and use the correct mix, and good ing into service such things as fruit boxes, seed commercially in strips of expanded The blocking machines produce either results should be obtained. plastic and polystyrene cartons and kitchen polystyrene which contain holes for seed and square or hexagonal blocks about 2 in high, foil or plastic food containers. Cleanliness and soil mix. This material is heat-retentive and with a depression in the top for the seed to be Seed flats good drainage are the main conditions; when easily broken to release the plants on planting sown or the seedling pricked on. To make a Just as plastic pots have replaced clay ones, they are achieved just about anything will do. out. However, the strips can only be used batch of soil blocks, moisten some special so wooden seed flats have been superseded There is, however, no substitute for the neat once. Plastic sleeve pots, also widely used blocking mix in a bucket or bowl. Test by plastic. Flats are vital for raising larger appearance of a bank of clean plastic or commercially, can be used for pricking on the moisture content by squeezing. If the numbers of seedlings. Many propagating wooden flats. seedlings which are later to be planted out. mix crumbles a little, it is ready. If it falls cases are designed to take the standard-sized When filling such non-rigid containers with apart, it is too wet. If it does not start to seed flat, which measures 14in x 81/2in x 21/2in. Other equipment soil mix care must be taken to fill all the crumble, it is too moist. Push the mould into Half-sized flats, 6 in x 81/2 x 21/2, are also used. A sieve with a 1/2 in mesh, a further fine sieve, corners to avoid air pockets. the damp mix and when it is full depress Plastic flats must be well drained and rigid, and a supply of labels will be required.

Potting

Crock the pot to provide adequate drainage. Hold the plant in the pot by a leaf and pour Firm gently with the finger tips to avoid air Place the potted plants in a position with Moisten a supply of potting soil and water in compost with a circular motion. Tap the pockets around the roots of the plant. good light and water to settle the soil the plants to be potted. pot to distribute the soil. around the roots. Pots and potting 3

Potting procedure 2 ft deep. The sides and back can be 6-12 in the seedling and roots from the soil. Place surface and the pot rim to allow for efficient Potting, re-potting and potting on are some high. The bench can be placed in the green­ the plant in the pot and pour fresh soil watering. As a guide, aim at a space equal to of the most frequent tasks the greenhouse house or in a shed or outhouse, wherever around the roots. Make sure that the plant is one-seventh or one-eighth of the depth of gardener faces. While they are not difficult, there is space. If the bench is in the green­ not potted too deeply—the base of the stem the pot. As much water as will fill this space the basic techniques should be mastered, for house, be sure not to leave surplus soil should be level with the surface of the soil. should thoroughly wet all the soil with a if plants are not potted properly, no amount lying on it or on the floor, where it will attract Distribute the soil around the roots with a little surplus trickling out at the bottom. of subsequent care will make them grow to pest and disease organisms. circular motion of the hand or trowel. Tap their full potential. Preparation Assemble the pots, drainage the pot gently on the bench to settle the soil Potting on Potting is the initial transfer of a seedling, material such as crocks if needed, and the around the roots. Make sure that the plant When the young plant has filled its container rooted cutting or bought-in plant to a pot or soil mix. Carefully choose pots no larger is centered in the pot. If roots still show with roots it will need potting on, that is, other container. Potting on is its transfer to a than necessary: most plants grow and look after tapping, add more potting soil, then removing from its container and placing in a larger pot as it grows. Re-potting is move­ better in small rather than large pots. Use firm lightly with the fingertips. A further tap larger one. First water the plant, but do not ment to a new pot of the same size as the old, a soil mix suitable for the plant being grown, on the bench will level the soil leaving it soak it. Invert the pot onto an open hand the prime object being to renew some of the and make sure that it is well mixed. Soil ready for watering. The degree of firming with the plant stem hanging down between soil mix around the rootball. should be damp but not wet. It should be can vary with the type of plant and soil the middle and index fingers. Gently rap the The potting bench The first step is to have a possible to pour it cleanly into the pot by type. All-peat mixes require little firming, pot rim on a firm wood surface, or tap it with proper work surface for potting. A bench or hand or with a trowel. tapping followed by watering will settle the a light hammer, and lift the pot off. If this table with a back and sides allows the soil medium amongst the roots. Loam-based operation does not work the first time, the mix to be piled up. If there are never more Potting mixes, particularly when used for vigorous plant may be too dry and watering should be than a few plants to pot at a time, construct a Seedlings or cuttings growing in flats or pots plants, can be made firm with light finger repeated before trying again. Prepare a new portable bench from a 2 ft square board with should be watered. Loosen them from their pressure. The former practice of ramming pot which should be large enough to allow a retaining rim 3-4 in high around three sides. container by knocking the sides. Remove soil firm with a potting stick is now con­ about an inch gap all round the rootball to This board can be rested on the greenhouse seedlings carefully, holding them by the seed sidered unnecessary. the right level, then fill the gap with fresh soil, bench when required. A permanent potting leaves, not the stem. Keep the rootball as When the potting operation is completed tapping and firming as described above. bench should be at waist height, 3 ft wide and large as possible. Use a dibble to help free there must be a space between the soil Water to settle the soil.

Potting on PEAT PELLETS

Peat blocks and pellets allow seedlings to grow and be transplanted without root disturbance. The plants should be potted or planted out when the roots emerge Water the plant. Select a pot 1 in larger than Hold the plant stem between the fingers Place the rootball in the new pot and from the block. The netting will decom­ the present pot and crock it if necessary. and invert the pot, tapping gently so that sprinkle moist soil around it. Firm pose in the soil. the rootball slides out. carefully. Pots and potting 4

Re-potting fresh soil in the base of the pot and put Hanging baskets MAINTENANCE OF CONTAINERS Re-potting is carried out when the plant has the plant back in position. Push more fresh Baskets made from wire, without a drip-tray, reached as large a size as is required and soil in around the sides, making sure there must be lined with sphagnum moss before If looked after, pots, tubs, boxes and other the status quo needs to be maintained. The are no air pockets left and that the soil is the mix is added. Black polyethylene is a containers will last for many years. Once aim is to replace some of the spent soil pushed around the roots. Firm the surface more convenient but less traditional and less plants are removed from them they should around the rootball. Re-potting is necessary of the soil, and water. attractive lining. It must be perforated. be washed in a mild disinfectant, dried and every year or every other year. Check the Use John Innes No. 2 potting compost for stored in a dry place. Wooden container! cultural instructions for the plant concerned Top-dressing hanging baskets, as its loam base holds should be treated with a non-toxic: pre­ for advice on the frequency of re-potting. Top-dressings of fresh soil are applied to moisture well. Peat-based mixes can be used servative, ideally coated inside with .in Some species resent disturbance, in which beds, borders and containers. When used but they tend to dry out in the exposed asphalt paint. If metal cans are used as case they should be top-dressed (see below). on pot plants the process of top-dressing environment of a basket and are hard to substitute containers, make sure that they It is best done when the plant is resting or serves the same function as re-potting. It is re-wet. Place a layer of moss in the bottom are painted with non-toxic paint to pre dormant in late autumn. Remove the plant more practical than re-potting on very large of the basket and weigh it down with moist vent rust. Some improvised plastic; con­ from its pot and reduce the size of the root- plants which are difficult to re-pot, and is mix. Add one or two trailing plants and firm tainers will tend to become brittle under ball by up to a quarter, using a small hand fork essential for those plants which resent the more mix around their roots. Proceed by the effects of the ultra-violet component and a sharp knife or shears to prune any disturbance of re-potting. During the dor­ building up layers of plants and mix, pushing of sunlight. thick roots. On larger perennial plants such mant season, strip away the top layer of the trailing plants through the basket so that Clay pots are expensive to replace and as fruit trees and bushes, prune the top soil and any small roots. This must be done they can hang down the sides. Build up the should be wired or riveted to prevent growth by the same amount as the roots. This carefully and any of the thicker roots en­ layer of moss around the sides, keeping it breakage. Unless completely shattered, ensures that the plant remains balanced. If countered should be left. On completion, above the level of mix at all times. Place up­ broken pots can be repaired very satis­ necessary, tease out the roots from the root- fill the gap with a rich mix such as John right plants in the final layer of mix so that factorily with waterproof ceramic glue. ball using a fork or stick. Remove some of the Innes No. 3. Firm the mix carefully and they grow upwards from the basket. Hanging Those based on epoxy resin are strong and old spent soil from the rootball, without water lightly. Top-dressing is usually carried baskets should be replanted with fresh permanent. It is rarely possible to repair damaging the roots if possible. If the same out in early spring, just before the plant material each year so potting on and re­ broken plastic pots. Wooden containers pot is to be used, clean it well. Place some begins to grow again. potting do not arise. can often be mended using screws or nails. Use greased brass screws when Re-potting assembling large wooden containers.

To strengthen a cracked clay pot, wrap galvanized wire around the pot and twist the ends gently together. Keep cracked pots scrupulously clean, for the cracks Remove the plant from its pot as described Trim the roots with sharp scissors, knife or If the old pot is to be used, clean it well. can harbor dirt and pest and disease under potting on. Remove some of the shears. On larger plants, prune top Replace the rootball and add fresh soil, organisms. spent soil from the rootball by loosening. growth In proportion. firming well. Growing from seed 1

One of the most satisfying aspects of garden­ Growing from seed an example of the often complex dormancy board so that the soil comes level with the ing under glass is raising plants from seed, In the wild, all flowering plants reproduce factors that are inherent in some seeds. The rim. Firm the soil down with a presser, then cuttings or by other propagation methods. themselves by seed and in the garden too this seeds of a few plants benefit from a dry warm sow the seeds evenly and thinly. Many plants can be raised with a minimum of is an important method of increase. It must be period because, though superficially ripe, Seeds which are large enough to handle equipment and skill, while with practice and borne in mind, however, that many garden they are not fully mature within. Some seeds either with the fingers or flat-tipped forceps patience the ability to cope with the more plants are of mutant or hybrid origin and have chemical inhibitors in the seedcoat are best space-sown, that is, each seed should difficult plants grows quickly. may not come true to type from seeds. For which normally leach out during heavy rain­ be placed in position sufficiently far apart The main methods of propagating green­ such plants, vegetative propagation methods fall. Seeds in this category should be soaked each way that subsequent seedlings can house plants are by seeds and stem cuttings. are required. Make sure that home-saved in cold water for 24 to 48 hours before sowing. develop without crowding. Larger seeds such Less important methods are layering, offsets, seeds are from healthy plants. This simulates the natural leaching process. In as sweet peas can be sown singly in batteries bulbils, root cuttings and leaf cuttings. Growing conditions In order to germinate general, most tropical and sub-tropical plants of small pots, soil blocks or peat pellets to Propagation equipment ranges from the successfully, seeds must have moisture, air do not have these dormancy problems. If save both initial pricking-off and potting. Use most basic improvised tray to the sophistica­ and a suitable temperature. The temperature there is any doubt as to when to sow seeds, the presser again to push the seeds into the tion of a mist unit. Equipment is described on they need varies widely, depending upon the particularly if home-saved, sow half when surface so they are not moved during the page 30, containers on page 51. The purpose species or variety. The majority of greenhouse gathered or received and the other half the covering operation. o o of propagation equipment is to provide the plants will germinate at 15°-18 C/60 -65°F, a following spring if the first batch has not Very fine seeds such as those of begonia optimum environment, in terms of tempera­ temperature easy to maintain in a home already germinated. Alpines grown from seed and lobelia are difficult to sow evenly and are ture, irrigation and humidity, for the plants. propagator. Some of the plants raised under need special treatment. See pages 88-90 on best mixed with some fine dry sand to aid Hygiene With all aspects of propagating, glass for setting outside will germinate at the alpine house. dispersal. Fine seeds of this sort do not need hygiene is vital. The seed sowing or rooting lower temperatures, around 10°C/50°F or Soil and containers Pre-mixed seed sowing covering. Larger seeds should be covered medium should be sterilized and all con­ less, while many tropical plants need mixes (composts) are available commercially, with a layer of fine soil equal in depth to the o o tainers scrubbed clean before use. Between 24 -26°C/75 -80°F. As a rough guide, a some containing loam, as in the John Innes longest diameter of the seed. This is best done each batch of propagation, the case or frame suitable germinating temperature is at least formula, while others are all peat. Both sorts through a fine mesh sieve. should be washed inside with disinfectant. five degrees above the minimum required by are suitable for most greenhouse plants. For Aftercare Watering should be carried out as (See page 32.) Check all cuttings regularly and the plants when growing. details and mixtures see page 42. When a few soon as the seeds are sown, using a fine-rosed remove all leaves that are fallen and any When to sow The best time to sow seeds plants only of each species are needed, small can or by immersion. Immersion is best for which are yellowing or browning. Take pre­ varies with the species, but in general early pots or pans of 3-4 in diameter are ideal. very fine seeds as overhead watering may cautions against damping-off disease of seed­ spring suits most plants. The seeds of many Sowing Fill each container above the rim, tap disturb or clump them. Place the pot in a lings (see page 33). Make sure that the stock hardy plants need a cool period after sowing it gently on the potting bench, then strike bowl or deep tray filled with water so that it plants are free from pests and diseases. before they will germinate properly. This is off the surplus soil with a straight-sided comes at least halfway up the pot. As soon

Seed sowing

1 Fill a container with 2 Firm the soil with a 3 Space-sow seeds which 4 Press the seeds into the 5 Water by immersion, 6 Cover containers with a soil mix, tap it, then presser to within \ in of the are large enough to handle surface of the soil. Cover placing the container in sheet of glass or plastic strike off surplus soil rim. Sow the seed thinly with the fingers or a pair of with a thin layer of sieved water until the top of the and keep them away from with a board. and evenly. forceps. soil. soil darkens. direct sunlight. Growing from seed 2

as the surface of the soil darkens and glistens turer's instructions. Additional feeding is tainer. Push the soil gently around the root to the stage when their leaves start to over remove the pot and place in the appropriate necessary because many seed mixes con­ and firm each seedling lightly with the dibble. lap, they are ready lor potting or hardenning, germinating temperature. tain only a phosphate fertilizer, and other The distance apart at which seedlings off and planting out. To prevent undue drying out of the soil nutrients are necessary for healthy plant should be set varies with its size. Very small during the germinating period the pots growth. seedlings such as those of begonias can be Hardening off should be kept out of direct sunlight and set about 1 in apart, larger ones to 2 in or After the seedlings have been pricked off, placed either in a propagating case or Pricking off more. Bedding lobelia seedlings may be they have to be gradually weaned to a stage covered with sheets of glass. If direct sunlight Once the seedlings are seen to be ready for pricked off in groups of two or four to make at which they can be planted out and survive is likely to fall on them, they must be shaded pricking off, fill pots, pans or boxes with the handling easier. The equally small begonias cool temperatures, fluctuating water condi­ with sheets of cardboard or newspaper to chosen potting mix as described for seed can be treated in the same way but are best tions and the effects of wind without their prevent scorching. This covering is important, sowing. Lift the seedlings with care. If in quan­ kept singly. To aid handling, each tiny seed­ growth rate being affected. This process is for if the soil surface dries out just as the tity, small clumps should be dug out with a ling can be picked up with a notched-tipped called hardening off. seeds are germinating it can be fatal, especi­ dibble or a stout wooden label, then teased flat stick or plant label. Once the pricked-out seedlings have re­ ally to very small seeds. apart, taking care to handle them by the seed Once pricking off is completed, each pot, established, move them to a cold frame, Germination Inspect the seed containers leaves only; damaged seedlings should be pan or box must be watered carefully with a which should be kept firmly closed. Gradually regularly and either wipe off the condensation discarded. fine-rosed can and returned to the same en­ air the frame during the day by raising the lid, or turn the glass over. After the first week to Where a few seedlings are growing in a vironment. When the seedlings have grown until the frame is open continually. ten days, examine daily to catch the first small pot it is best to tap out all the seedlings signs of germination. Once the seedlings are and soil, and then to shake or tease them GERMINATION seen pushing through the soil, remove the apart. If there is little or no root branching, covering and bring into good light, but shade seedlings can be left to make small plants for On germination, each seed produces one get under way. So, if the seed has not been from direct sunlight for the first week or so. direct potting later. primary root or radicle, a stem known as a soaked before sowing, it is important that If the seed was sown too densely or more Make planting holes with a dibble, a cylin­ hypocotyl, and one or two seed leaves or the soil should be watered immediately seedlings appear than were expected, it is drical stick like a blunt-pointed pencil and cotyledons. Flowering plants are classi­ after sowing. advisable to spray with captan or zineb as thick enough to make a hole large enough to fied by the number of seed leaves they Once the seed has sufficiently imbibed, a precautionary measure against damping- take the seedling root comfortably. Dibbles produce. The monocotyledons, which in­ the embryo inside the seed begins to off disease. of differing thickness will be needed for seed­ clude all members of the lily, amaryllis, produce root and stem systems, which Feeding If seedlings are to be kept in the con­ lings of varying size. Each seedling should be onion and agave families, produce one eventually break out of the seed. tainer for some time, they should be given a inserted at the same depth or a little deeper usually grassy seed leaf. The dicotyledons, To grow, the embryo uses its food liquid fertilizer according to the manufac­ than it was when growing in the original con­ which include most other vegetable and reserves. When oxygen is combined with flower families and all the broad-leaved carbohydrates in these food reserves, the Pricking off trees and shrubs, have two, usually energy necessary for growth is produced. rounded or oval seed leaves. All growth processes within the seed are There are some anomalies to this appar­ chemical reactions activated by the addi­ ently straightforward classification. Some tion of water. To develop successfully, the members of both groups retain their seed seed needs an increasing quantity of leaves as food stores below ground, the water, and the soil used must be capable first leaves to appear being true ones. of holding these amounts. Familiar examples are broad bean, sweet As all the processes involved are basic­ pea, oak and palm. ally chemical reactions they will obey The germination of seeds covers the normal physical rules, the simplest of entire process, from subjecting a resting which implies that the higher the tem­ seed to suitable conditions to cause it to perature is raised, the faster will be the develop to the stage at which the seedling rate of the reaction. In practice, this produces true leaves and establishes as a means that the warmer seeds are kept, young plant. If a seed is subjected to the the quicker they will germinate. As all conditions required for germination, and these reactions are taking place in a it fails to germinate, despite the fact that biological context, there are biological 1 Lift seedlings in clumps with a wooden 2 Make planting holes in fresh soil with a it is alive, then the seed is described as limitations as to how high the temperature label or a dibble, then tease them apart, dibble, and insert the seedlings to the being dormant. can be raised. Higher temperatures are taking care to handle them by the seed correct depth. Firm the soil lightly around Water is vital to allow plant growth to also more costly to maintain. leaves only. the roots with the dibble. Cuttings 1

Growing from cuttings is the most popular closed cases if a mist unit is not available. method of vegetative propagation. Cuttings A moist but well-aerated rooting medium TYPES OF CUTTINGS are severed pieces of stem, leaf or root in­ must be used in all cases. John Innes seed duced to form roots and shoots and develop compost, all-peat seed and cutting mixes, and into young plants. The advantage of this the 50/50 sand and moss peat mixture (see method of vegetative propagation is that page 42) are all suitable. For difficult plants every young plant will be identical with its use pure sand, which must be coarse and parent and often will flower and fruit sooner well washed. There are no nutrient minerals than a seedling. The severed piece of the in sand and almost none in peat, so once the plant is detached from its parent and has to cuttings start to root a proprietary liquid ferti­ survive while it develops a root and shoot lizer should be used at each watering until system and becomes a complete plant. potting is carried out. Potting should be Therefore, it is vital to provide an environ­ done as soon as the cutting is well rooted. ment that will induce the production of new root and shoot growth as fast as possible. Selecting and taking cuttings Cuttings should always be taken from vigor­ Stem cuttings ous plants, which are young and healthy in Depending on the species and variety and the themselves. If possible, the parent plant age of the plant, stem cuttings take anything should be severely pruned to encourage it to from about ten days to several weeks to pro­ produce faster-growing shoots from which duce roots and start to grow. The younger the cuttings can be made. If it is anticipated that a parent, the faster the cutting will root. This is a large number of cuttings will be taken from factor often overlooked and it must be a one parent, the parent plant should be pruned major influence on the choice of plant hard to encourage the growth of new shoots. Heel cuttings can be made from soft, Mallet cuttings consist of a side-shoot and material when taking cuttings. During this Growth-controlling chemicals called hor­ green, semi-ripe or hardwoods. Strip a a section of the main stem. They are taken period they must be kept alive and in a mones are responsible for the rooting of young side-shoot away from the main from semi-ripe and hardwoods. The plug healthy condition. To cut down water loss as cuttings. In many cuttings enough natural stem so that a strip of bark comes away. of mature wood helps prevent rotting. much as possible, all leafy cuttings must be hormone is present to initiate rooting but it is kept in a "close" or humid propagating case recommended that one of the proprietary or improvised container. hormone rooting powders is used as a stan­ The rate at which a stem cutting develops dard procedure. These powders also usually its roots is dependent on the temperature contain a fungicide to combat rotting. around it. The higher the temperature, within The ability of the propagating material to reason, the faster the root-triggering chemical regenerate roots and shoots depends on its reaction and thus root production. However, stage of development. This is particularly if the whole cutting is kept warm, the tip true of woody-stemmed plants. Some root should begin to grow and food will be diverted best from soft shoots, others as the shoots from the important function of forming roots, begin to get woody at the base, and yet others thus weakening the cutting. Therefore, a stem when they are fully woody. Four categories of cutting ideally requires cool air to retard the development are generally recognized. These growing tip, and warm soil to encourage root are softwood, greenwood, semi-ripe and production. hardwood stem cuttings. The box right illus­ The exact temperatures vary with the con­ trates some of the ways of taking cuttings. dition of the stem and how susceptible it is Heel cuttings are short stems pulled away to water loss. Softwood and greenwood cut­ from the main plant. The heel is the thin sliver tings require bottom heat of about 21C/70°F of plant material that tears away from the and as cool an aerial temperature as practic­ main stem. Mallet cuttings incorporate a able—a mist unit with soil heating is ideal. section of main stem on either side of the Softwood stem cuttings are taken from the Leaf-bud cuttings can be taken from any Semi-ripe and evergreen cuttings may be side-shoot chosen for propagation. Softwood tips of the current season's growth. Hor­ type of wood. They consist of a short piece rooted in a similar environment, although and other cuttings are often taken from the mone powder is not needed, but it is good of stem with a leaf and a bud in its axil. The less bottom heat is required. Some may also tips of branches. Leafbud cuttings consist of practice to dip the cutting in fungicide. leaf chosen must be fully mature. be rooted successfully in cold frames or a whole leaf, bud, and short piece of stem. Cuttings 2

Softwood stem cuttings Vigorously growing heat. Softwood cuttings are extremely choose lateral shoots as cuttings, each one will still lose some water by evaporation from shoots of non-woody plants, or fast-growing susceptible to water loss. A mist unit thus being either sliced or gently pulled off with a their surface. The commonest reason why tips of potentially woody stems, are used as provides a very high quality environment. downwards movement so that a sliver or heel these cuttings may fail to develop roots is softwood cuttings. Softwood cuttings are Aim for a rooting medium temperature of of the parent stem is attached. If a tail of because they are allowed to dry out. To avoid taken in spring or early summer. The stems 21°-24°C/70o-75°F. Spray with fungicide on tissue extends from the heel this should be cut water loss, expose as little of the cutting ,is are best gathered in early morning when at insertion and weekly thereafter. away cleanly. If the tip of the semi-ripe cut­ possible above the ground. However, it the maximum turgidity. If the cuttings are not to Greenwood stem cuttings Greenwood cut­ ting is soft it should be removed. Cut off the cutting is planted too deep, the buds will not be used immediately, place them in a bucket tings are taken in early summer from the soft lower foliage, leaving about a third of the grow properly. Thus it is vital to expose of water. An exception is the zonal geranium tips of the stems, just as the main flush of cutting bare. Insert them in the same way as sufficient of the cutting above ground for which roots better after cuttings have been growth slows down but before any sort of softwood cuttings. Semi-ripe cuttings taken about three buds to develop. Keep the left exposed and shaded for a period of woodiness is observable. They differ from in late summer should be left in the cold cuttings cool to prevent dormant buds 24 hours. softwood cuttings only in their speed of frame until the end of the following growing developing and diverting energy from the Trim each shoot to 3 in long, cutting cleanly growth. Treat them in the same way as season. Feed regularly to encourage vigor­ developing roots. just beneath a node or leaf. All leaves on the softwood cuttings, rooting them in a mist ous growth. Lift and transplant the new basal third to one half should be removed. unit or a heated propagating case. plants in autumn. Leaf-bud cuttings Place a 4-6 in layer of the chosen rooting Semi-ripe stem cuttings This category is a Hardwood stem cuttings This method is sel­ Leaf-bud cuttings may be taken from any of medium in the bottom of the propagating stage further from green wood, each cutting dom used under glass, though it is suitable for the types of stem. Each cutting consists of a case, or fill boxes or pots. If there are only a being made from shoots which are hardening bougainvillea and a few other shrubs and leaf, a bud in its leaf axil and a very short piece few cuttings of each species, 3-4 in pots at the base. Such cuttings are taken in late climbers that have a fully dormant period. of stem. The leaf supplies food to support the make best use of propagating room. This is summer. Semi-ripe cuttings can be rooted in Growth will have then ceased and the stems cutting and the regenerative processes; the particularly useful if several species are being poorer light and lower temperatures than will be fully mature. Use 6 in pieces of mature bud is the basis for the new stem system; and propagated which have a wide range of softwood or greenwood cuttings, and can wood which have dropped their leaves. Treat the piece of stem is where the first roots are rooting times. Insert the cutting into the thus be grown in a cold frame. with hormone powder and insert them in a produced. rooting medium so that about one-third of Cuttings should be 4-6 in long, and it is closed frame within the greenhouse. Leave New stems produced by pruned plants its length is in the soil, water and place often advantageous for them to have a heel about half the length of the cutting above soil have the best chance of success. Select one in a propagating case, ideally with bottom of older wood at the base. To obtain a heel, level. Hardwood cuttings, although leafless, of these new stems with an undamaged

Softwood cuttings

1 Gather shoots from the 2 Trim each shoot to 3 in 3 Fill pots or trays with 4 Water the cuttings and 5 Spray the cuttings with 6 When the cuttings have tips of vigorously-growing long, cutting below a node soil mix. Make planting place in a propagating case a dilute fungicide on rooted, gradually reduce plants. If possible, take or leaf. Remove leaves from holes with a dibble and or mist unit. The rooting planting and weekly bottom heat and when they cuttings in the early the bottom third of the insert the cuttings. medium should be kept at thereafter. Label the have hardened off pot using morning. cutting. 21o-24°C/70o-75°F. containers. John Innes No. 1 compost. Cuttings 3 mature leal, insure that there is a viable bud on the opposite side of the stem from the bud. insertion. If they are inserted vertically, make in the bottom of the stem of plants that are in the leaf axil. Label the pot and stand it on a greenhouse sure they are the same way up as when difficult to root. Dip the base of the cutting in Cut close above the bud so that as small a bench or in a closed case—the higher the growing on the plant. Each cutting will have rooting hormone powder. Ensure the cut snag as possible is left. This minimizes the temperature, the faster will be the rate of several incipient buds, one to three of which surface is covered with the powder. likelihood of rotting and die-back. Make the regeneration. may grow into aerial shoots. Plant the cutting up to its leaves in a cold basal cut about 1-11/2 in below the top cut so Water the cutting to prevent it drying out. frame or mist unit. Allow the leaves of cuttings that sufficient stem is available to anchor the Do not overwater during the winter when Evergreen cuttings to touch but not to overlap. cutting firmly in the growing medium. Apply the cutting is dormant, as the soil will Evergreen cuttings are taken from stems of Aim for cool, moist conditions by shading a rooting hormone. Insert the cutting with readily waterlog, causing the cutting to rot very ripe wood. Unlike hardwood cuttings the frame until light intensity becomes lower its bud level with the soil surface. Place and die. Harden off the cutting once it has they are not leafless and are not fully dormant in winter. Leave frame-grown cuttings in place cuttings of the more hardy plants in a cold rooted, and transplant in spring. Label it. because of their evergreen habit. Because for the whole of the next growing season. Pot frame and cuttings of less hardy plants in a they have leaves, the cuttings need extra care on mist-unit cuttings in spring, taking care not well-lit protected environment such as a mist Stem sections to prevent excessive water loss. to damage the roots. unit or closed case. It may be necessary to A few greenhouse plants, notably Dietlen- Take evergreen cuttings, from a pruned Evergreen plants can be propagated from support large-leaved plants such as Ficus bachia (dumb cane), Dracaena and Cordyline, plant if possible, during later summer to early softer wood earlier in the growing season. elastica with a short length of cane inserted become leggy with age, the lower stem be­ autumn; rooting will normally take place Treat these cuttings according to the con­ next to each cutting to prevent it toppling. coming leafless. When the plant becomes during winter. Evergreen cuttings taken in dition (soft, green wood or semi-ripe wood) of The cane can be inserted through the rolled unattractive it can be cut back to just above late summer should be 4-6 in long. Take a their stems. leaf, which is itself secured by a rubber band. soil level. Sever the top of the removed stem heel with the cutting if it is to be propagated Vine eyes Vine eyes are the hardwood and use it as an evergreen cutting. Cut the in unsterilized soil in a cold frame or poly­ Conifers equivalent of leaf-bud cuttings taken while remaining bare stem into 11/2-2 in lengths ethylene tunnel. Neaten any tail on the heel. Some conifers, but not most spruces, pines the grape vine, or other woody plant, is leaf­ and insert these stem section cuttings verti­ Leave on the cutting any terminal bud that and firs, can be propagated from cuttings. less. Prepare the vine eyes as described above. cally with the top flush with the soil, or may have formed. If, however, growth is con­ Either a warm environment such as a propa­ Insert them horizontally with the bud just horizontally and completely covered by tinuing, cut out the soft tip with a knife. Strip gating case or a cold frame can be used. above the soil surface. If this method is chosen about 1/2 in of the rooting medium. It is advis­ the leaves off the bottom third of the cutting. Select young, actively-growing shoots and it will aid rooting if a sliver of bark is removed able to dip the sections into a fungicide before Make a shallow vertical wound about 1 in long take cuttings in autumn and winter.

Evergreen cuttings

1 In late summer, take heel 2 Trim the heel, pinch out 3 Make a shallow 1 in cut 4 Mix peat, grit and sand 5 Shade the frame and 6 The following autumn, cuttings of the current the growing tip and remove at the base of the stem. into cold-frame soil. Plant water well. In winter, transplant the rooted season's growth, from a leaves from the lower third Dip the cut area in rooting the cuttings in the frame up insulate the frame against cuttings, taking care not to pruned plant if possible. of the cutting. hormone powder. to their leaves. Do not frost if necessary. damage the fragile roots. Rooting is in winter. allow leaves to overlap. Label the plants. Leaves 1

Some greenhouse and house plants will Leaves of plants such as Begonia rex can be Choice of leaves Young yet fully developed up a mix of equal parts silted peat and grit develop plantlets on their leaves. In some cut into squares which will, given correct leaves should be chosen. If the leaf is still Fill a container and firm the mix to within cases this is done naturally, in others leaves conditions, each produce a plantlet. Succu­ growing, its energy will go into developing 1/4 - 3/4 in of the rim. Cut the chosen leal from are detached, treated in much the same way lents and some bulbs have the capacity to fully. This will delay the generation of new the parent plant with a clean sharp knife as cuttings, and the plantlets which develop produce plantlets from leaf sections. plant life in the form of plantlets. Since a About 2 in of stalk should be attached to the grown on. Although only a small range of leaf is unsupported by a root system, any leaf. Using a dibble, insert the petiole at a plants can be grown from leaves, this range Foliar embryos delay can be a source of problems. Select shallow angle in the mix. Firm the mix gently includes many of the most popular such as A few plants develop plantlets naturally. leaves that are complete, normal and un­ around the petiole. The leaf should be almost Begonia rex and the African violet Saintpaulia Examples are Tolmiea menziesii, the pig-a­ damaged, and free from pests and diseases. flat on the surface of the mix so that the ionantha. back plant, and Mitella. Some plants release It is possible to take leaf cuttings all the year stalk is in the topmost layer of the cuttings their plantlets naturally, on others the plant- round, so long as young complete leaves are mix, where air can penetrate. Insert the Types of leaf cuttings lets have to be separated from the parent available. remaining cuttings, label them and water with The simplest form of leaf cutting is a complete plant. Planting and aftercare Use a cuttings mix a dilute fungicide. leaf with a stalk. Such leaf-petiole cuttings made up of equal parts of sand and grit. The leaf cuttings will need an atmosphere can be taken at any season when a complete Propagation conditions When taking the leaves from the parent of high humidity, such as that produced in a young leaf is available. Midrib cuttings make Leaf cuttings of all sorts are vulnerable to plant, use a sharp knife or razor blade. Always heated propagating case. Bottom heat, use of the fact that a leaf midrib is an exten­ moisture loss and therefore must be kept in spray or water leaf cuttings with a fungicide maintaining a temperature of 20*C/68*F, is sion of a leaf-stalk and is able to regenerate a closed propagator, or under a glass sheet on planting. If the plantlets are slow to ideal. The cuttings must have sufficient light in the same way. Propagation by midrib or polyethylene tent. Bottom heat best develop, foliar feeding may be necessary. to develop, but should be shaded from direct cuttings is most successful from plants provides the warm, humid conditions re­ Do not feed until plantlet growth has begun. sunlight. having leaves with a single central vein, quired The most common cause of failure in In about 5-6 weeks, plantlets should begin such as Streptocarpus. Lateral vein cuttings leaf propagation is rotting of the leaf before Taking leaf-petiole cuttings to develop on the leaf stalk. Several may develop on the side-veins of a leaf after the it has a chance to become established. Leaf-petiole cuttings can be taken at any appear on each stalk, though the number is midrib has been cut out. Leaf slashing Hygiene is thus vital. All propagating equip­ time of the year when new leaves are avail­ variable. The number of plantlets that appear involves the growth of plantlets from cuts ment and containers should be clean, and able. Choose an undamaged leaf which has on each stalk is smaller than the number that made in a leaf without a central main vein. soil should be sterile. recently expanded to its mature size. Make each leaf will produce using leaf squares of Taking leaf-petiole cuttings

1 Cut an undamaged, fully 2 Insert the stalk at a 3 Spray the cuttings with a 4 Place the flat of cuttings 5 Alternatively, place a few 6 Pot on the plantlets once grown young leaf from the shallow angle in a flat of dilute fungicide as soon as in a propagating case at cuttings in a 3 in pot. they are large enough to parent plant. Cut near the cuttings mix. Firm the they are inserted. 20°C/68°F. Shade lightly to Cover with a polyethylene handle. Harden off by base, and trim the stalk to mix gently around the protect the cuttings from bag supported on wire. reducing heat and increasing about 2 in. stalk. direct sun. Place in a warm, light room. ventilation. Leaves 2 leal slashing. When the plantlets are suffi­ Monocot leaves Taking leaf square cuttings ciently large to be handled, pot them on into Some plants have monocotyledonous leaves, |ohn Innes No. 1 or equivalent. Liquid that is, leaves with a series of parallel veins feeding may be necessary if the plantlets running along the length of the leaf. Such have to remain in the original cuttings plants include bulbous species such as mix for any length of time. The popular hyacinth and snowdrop, and succulents African violet, Saintpaulia ionantha, is often such as Sansevieria (mother-in-law's tongue). propagated from leaf-petiole cuttings. Other Leaves from bulbous plants are delicate and plants that respond to the method are should be handled as little as possible. begonias (other than Begonia rex), Peperomia Take a mature leaf and cut into 1 in sections caperata, and P. metallica. across the veins, using a sheet of glass and a sharp blade as described above for leaf Taking leaf square cuttings squares. Insert the cuttings vertically in Unlike the leaf-petiole method, the leaf cuttings soil or mix. Spray with fungicide and square cuttings technique allows a large place in a warm (21°C/70°F), humid environ­ number of plants to be propagated from a ment. single leaf. It is mainly used to propagate New leaves used for propagation from Begonia rex and related species. bulbs in spring will take four to six weeks to Take a fully expanded, undamaged young produce plantlets. Pot up the plantlets once leaf from the parent plant. Lay it face down on they are large enough to handle. a sheet of clean glass and cut the leaf into a series of squares. Each piece should be Grafting roughly 3/4 in square. Be careful not to crush Grafting is not a common method of pro­ 1 Carefully cut a large fully 2 Lay the leaf face down on 3 Place the leaf squares 1/2 in the leaves when cutting. Prepare a flat of pagation in the amateur greenhouse, though grown young leaf from the a sheet of clean glass. Cut apart on the surface of a cuttings soil and firm it to within 1/4-3/8 in of it is used by professionals and in the open parent plant, cutting near the leaf into squares, each flat of damp soil in a warm, the rim, water it well and lay the leaf squares garden to propagate shrubs, roses and fruit the base. about 3/4 in across. humid environment. on the soil surface, face upwards and about trees. The main purpose of grafting is to j in apart. Label and spray with a dilute replace the rootstock of a given plant with fungicide. Do not water leaf squares, but another, compatible rootstock. This can irrigate if necessary by standing the flat in have the effect of restricting the growth of a bath of water. the plant, conferring resistance to disease, or Place the flat of cuttings in a closed promoting vigorous growth. The process is propagating case with bottom heat and not technically difficult, and grafting can keep them at a temperature of 18-21°C/65- form an enjoyable area for experiment. Full 70°F. Avoid direct sunlight, but allow the details may be found in the companion cuttings enough light to begin development. volume in this series, Plant Propagation. Plantlets should begin to appear after 5-6 weeks. They should not be detached from MIDRIB CUTTINGS the leaf square and potted on until they are large enough to handle. Gradually harden off Leaves with pronounced central ribs can the plantlets by admitting air to the pro­ be used as propagation material in the pagating case and reducing the temperature. same way as whole leaves with stalk Leaf slashing Begonia rex can also be pro­ attached. The midrib is an extension of pagated by leaf slashing, a technique similar the stalk, and when cut into sections to propagation from leaf squares. Choose a plantlets will develop from the cut sur­ large mature leaf, lay it on a sheet of glass, faces of the rib, given the correct condi­ and instead of cutting it into squares, make tions. Cut leaves of Gloxinia, Streptocarpus 3/4 in cuts across the leaf veins. Aim for one cut and similar plants into 1 1/2 in sections. every square inch. Place the leaf face up on Insert vertically in flats of soil and treat 4 Spray the cuttings with 5 Harden off young 6 Pot on the plantlets damp soil, and secure it with a wire staple. as leaf square cuttings. Plantlets should dilute fungicide. Shade from plantlets by increasing when they are large enough Treat as leaf squares above. Plantlets will appear in 5-6 weeks. direct sunlight. ventilation and reducing to handle John Innes No. 1 develop at the cuts. temperature. or equivalent. Other propagation methods 1

Air layering Air layering the moss in place with a square of black While cuttings are induced to form roots after polyethylene wrapped around to form a tube being detached from the parent plant, air and fixed in place with tape. The black poly layering is a technique which induces the ethylene will keep in moisture, keep out light growth of roots on stems still attached to the and maintain the correct warm, moist en parent. Its main use in the greenhouse is to vironment for root formation and growth, propagate Ficus elastica, though it can also be Aftercare and potting Air-layered plants will used on citrus trees and on shrubs. normally take at least a growing season to Air layering is carried out in spring or late establish themselves. Towards the end of the summer on growths of the current season dormant season after the first growing season, that are becoming woody. The necessary prune back any new growth above the conditions for root formation are restriction layered section. Cut the stem just below the of the chosen stem and the exclusion of light. bottom of the polyethylene-clad section and The roots thus stimulated are encouraged by carefully remove the polyethylene and the damp, moist conditions. tape. The moss should be combined with Preparing a stem Trim off the leaves and side­ the new roots to form a rootball. Cut away shoots of a straight stem to between 6 and the section of stem below the new roots, 12 in from the tip. Girdle the stem with a sharp slightly loosen the rootball and plant < art­ knife and apply hormone powder. fully in a pot of John Innes No. 1 or equivalent Applying the rooting medium Sphagnum Firm gently to avoid damaging the roots. moss, which is well aerated and holds mois­ ture, is the best rooting medium. Soak a hand­ Bulb scaling ful of moss thoroughly and squeeze it to Bulbs increase naturally by producing bulb­ 1 In spring, trim leaves and side-shoots 2 Apply hormone power to the cut. remove excess moisture. Work it into an lets or offsets but this method is slow. A faster from the chosen stem. Girdle by cutting Squeeze a ball of wet sphagnum moss interwoven ball of fibers 2-3 in in diameter, method of propagation is bulb scaling. This off a 1/3 in ring of bark with a sharp knife. around the girdled stem. split and place around the girdled stem. Hold can be done with lily and f ritillary bulbs. These

3 Wrap a square of black polyethylene 4 Towards the end of the following dormant 5 Then cut the stem below the poly­ 6 Pot into John Innes No. 1 or equivalent, around the moss ball. Secure top and bottom season, prune any new growth above the ethylene. Remove the polyethylene, taking firm in gently and place in the greenhouse with tape. Leave for a growing season. layered portion. care not to damage the delicate new roots. until new growth begins. Other propagation methods 2 bulbs have relatively narrow scale leaves Division Bulb scaling which can be readily pulled off the bulb's I he garden technique of propagating peren­ basal plate, nials by division is practiced in the green­ lake scales from fresh, healthy bulbs, house. Mature plants which have become too preferably in October or November. Cut only large can be divided, as can those fibrous- a few scale leaves from each bulb. Treat all crowned plants which become woody in the scales with a fungicide such as captan by center and only produce new growth at the shaking them in a bag with fungicide powder. edges. Dahlias and tuberous begonias can be Place the scales in sterile cuttings mixture or divided but grow better from cuttings or seed. damp vermiculite and seal the whole in a Greenhouse plants that can be divided in­ plastic bag. Store at 21°C/70°F until, in about clude arums, ferns, and some orchids. Plants 6-8 weeks, bulblets develop at the base of with fibrous crowns should be divided im­ the detached scales. When the bulblets mediately after flowering. Remove the plant appear, plant the scale leaves, with the bulb­ from its pot and dip the rootball in a bucket lets, in pots of potting mix or soil. Plant them of water. Then gently pull the crown into vertically with the tips just above the soil pieces of the required size. Tough crowns can mix. Water sparingly, and keep at 21°C/70°F be cut with a knife. Make sure that each piece until leaves are produced. At the end of the has a good eye or bud. Trim the long snoots season, after the leaves have died down, lift on the divided segments to balance the top- and separate the new bulbs, potting on or growth and roots and lessen water loss. Plant replanting them at once. in pots and water well.

1 In autumn, remove scale leaves from the 2 Place the scale leaves in a plastic bag outside of bulbs. Cut only a few scale leaves containing damp vermiculite or an equal from each bulb. Dust with fungicide powder. mixture of damp peat and grit. Blow up the bag, seal it and put it in a warm dry place.

All material propagated—seeds, leaves or Alternatively, paint a strip at the end of a cuttings—must be labeled. Otherwise it is seed flat white to form a writing surface very easy to lose track of what plants are. (b). When the flat is re-used a new layer of The label should show the date of sowing white paint can be applied to obliterate or propagation, the species and the variety. the label and provide a new writing sur­ Other information such as the source of face. the propagating material or reminders of Mature plants can have labels attached the conditions required may be added. to the stem. These can be made of plastic Labels can simply be wood, plastic or or light metal (c). Hand machines are avail­ 3 Six-eight weeks later, when bulblets 4 Place the pots in a warm (21°C/70°F) well- metal tags (a). Data can be written on these able which print labels on strips of plastic appear at the base, plant the scales upright lit place. New leaves will appear in spring. tags using a soft lead pencil or wax crayon. or punch letters onto lead strips (d). in John Innes No. 1 or equivalent and Harden off, and in autumn lift and separate cover the mix with grit. the bulbs. Replant as soon as possible. The year in a cold greenhouse 1

The year in a cold greenhouse than a protective covering against extremes and biennials can be raised from seed in the degrees above normal; this heat surplus not This calender details sowing and harvesting of cold, wet and wind. A cold greenhouse can predictable conditions a cold greenhouse only acts as a cushion against the rapid drop times for basic cold greenhouse crops and form a vital and interesting adjunct to the offers, and various propagation techniques in temperature as night falls, but also im­ lists planting, sowing and potting on times garden provided its limitations are recognized carried out. proves the growing atmosphere. Some of the for ornamentals. and the plants to be grown carefully selected. Despite the lack of artificial heat, the surplus heat is absorbed by the soil, paths Regular tasks such as watering, feeding, The most important limitation of the cold gardener has various techniques available to and structure generally, moderating night damping down, shading and ventilating are greenhouse is that of temperature. In winter, allow him to alter the environment of a cold temperatures as it is given off into the cooling not listed every month. The timing of these if the outside temperature drops to around greenhouse. The basic principles explained air. This mechanism is exploited by several procedures is to a large extent dependent 7°C/20°F it is likely that there will be several in the section on Running the Greenhouse solar heating systems upon day to day conditions and on the crops degrees of frost inside the greenhouse. It is (pages 32-33), apply here, though with the At all times the aim is to produce a buoyant being grown. Follow the instructions given wise to recognize this and to avoid trying narrow tolerance of many cold greenhouse atmosphere, one in which the air within the under individual crops, and act according to to over-winter plants which are not frost- plants extra care is needed. greenhouse is moving up and around rather the basic principles discussed in the first two hardy. It is possible to give protection against Ventilation The most effective method of than lying stagnant. sections of this book. frost by plunging pots and covering plants temperature control available is ventilation. Air movement The circulation of air is a vital Pest and disease control is another regular with polyethylene or burlap, but these pro­ In very cold conditions it can be colder in the factor in cold greenhouse management. Even task that must be attended to whenever vide limited defense against severe frosts. greenhouse than outside if the doors and in a closed-up cold house in winter, imperfec­ problems arise. The worst period for pests is lower ventilators are not opened for a few tions in glazing can allow air to escape suf­ from April to October, but problems such as Conditions and choice of plants hours in the middle of the day. Cold air is ficiently fast to give two complete air changes whitefly and red spider mite can appear in A cold greenhouse will suit those plants that heavy and collects in a pool at ground level, per hour. In high summer well-ventilated any of the 12 months. Follow the instructions are hardy outdoors, and will in most cases but will flow out if given the chance. greenhouses can have 120 air changes per on pages 33-40 for the control of pests and allow them to be grown better. It also suits Most ventilation is concerned with trap­ hour, which helps to keep internal tempera­ diseases. annuals, including fruits and vegetables, ping solar heat. Once outside temperatures tures close to those outside. If through a which are half-hardy outdoors. A cold green­ start to rise in spring, ventilators should be deficiency in ventilation air changes drop to Using a cold greenhouse house can extend the growing season at opened a little in the morning and closed 30-40 per hour, summer greenhouse tem­ A cold greenhouse is one which possesses no either end, allowing crops to be taken earlier some hours before sunset. This regime may peratures can rise as high as 43°C/110°F, to form of artificial heat. It is, in effect, no more and later than outdoors. Ornamental annuals well cause the thermometer to rise five the detriment of plants.

January February March April May June Plan the year's crops and order Ventilate as necessary. Water Sow lettuce, celery, carrots, Sow according to needs: lettuce, Plant eggplants, sweet peppers, Harvest lettuce, radish, endive, seeds and seedlings. Ventilate the sparingly. mustard and cress. radish, mustard and cress, beets, okra and cucumber, melons. mustard and cress, beans, parsley. greenhouse on sunny days. Sow lettuce, early bunching turnips, Sow in heat: eggplants, sweet endive, parsley. Sow sweetcorn, Harvest early carrots, early Continue to sow biennials. Pot on Sow onions for transplanting. Sow carrots, parsnips and early beets peppers, dwarf beans, tomatoes if celeriac, dwarf French beans, bunching turnips, beets. cyclamen seedlings. early radishes in soil borders or (until March), bulb onions (until not sown in February. cucumbers. Plant out tomatoes after last Take cuttings of pinks. Plunge peat pots. April). Sow tomatoes in heat later Prick out lettuce seedlings. Pot out Harvest early radishes and lettuce, frost. azaleas outside and feed every Bring in plunged bulbs to flower in in the month. late in month. chicory, seakale and rhubarb. Harden off bedding plants and 14 days. the greenhouse (Babiana, Bring potted strawberries in to crop Sow for transplanting: broad beans, Complete sowing half-hardy plant out after frosts have ended. Chionodoxa, Crocus, daffodils, in late spring. runner beans, brassicas, leeks, annuals. Sow biennials for spring Take cuttings from regal Fritillaria, Iris, Leucojum, Bring in remaining plunged bulbs to celery, peas, sweetcorn, chives, flowering under glass. Prick out pelargoniums. Sow Calceolaria, Ornithogalum.) replace those which have finished thyme. March-sown seedlings. Begin to Freesia, Schizanthus for winter Bulbs which have finished flowering flowering. Continue to bring in pot harden off bedding plant seedlings. flowering. can be planted out into frames. Pot on and divide ferns if necessary. strawberries. Take fuchsia cuttings, pot rooted Sow lily seed. Begin sequence of Pot on over-wintered coleus, Sow half-hardy annuals and alpines. dahlia and other cuttings. Pot up chrysanthemum cuttings later in fuchsias and pelargoniums. Pot on over-wintered annuals. Take tuberoses for flowering. Start the month. Sow and place in a propagating pelargonium and dahlia cuttings. feeding camellias. case: Abutilons, tuberous and Plant out rooted cuttings taken in fibrous begonias, Coleus, Celosias, winter. Plant hippeastrum bulbs in Gloxinias, Streptocarpus. pots. Pot on annuals sown in autumn. Re-pot evergreen azaleas. The year in a cold greenhouse 2

Excessive summer temperatures can be winter weather, is better than that of outdoor Over-wintering Successful over-wintering is for a large part of the year. These plants can reduced by damping down floors and walls plants. Blooms are more spectacular as wind more likely if certain precautions are taken. be used as the main display or to fill in gaps with city water, which rarely rises above a and rain damage is not a problem. During the coldest spells, plants must be kept between non-flowering permanent plants or temperature of 10LC/50"F. Damping down Alpines and similar plants can also be on the dry side. It is best that the roots do not fruit and vegetable crops. Hardy annuals can also promotes a degree of humidity enjoyed grown in an unheated greenhouse, but they freeze for these are often more tender than be sown in late summer or early autumn. They by most plants. Excessive transpiration caused require conditions which preclude the growth the tops. Ground level beds should be deeply will over-winter well in a cold greenhouse and by very dry, hot conditions gives a severe of many other plants. The running of an mulched with bracken or straw and the bases flower late the following spring, well ahead of check to plant growth. Shading, used in con­ alpine house is described on pages 88-90. of shrubs and climbers wrapped. Large pots their normal season. This technique can be junction with ventilation, is also important in Many food crops can be grown in a cold and tubs must be wrapped either with straw, used for hardy biennials, but these need to be controlling summer conditions. For full de­ house, providing cash saving over shop glass fiber, or any other approved insulating sown in early summer and may be grown tails of shading and ventilation practice, see prices and often produce of a higher quality. material that can be secured in place with outside or in an open cold frame until late pages 14-16. Tomatoes, the most popular crop, are covered netting or burlap and wire twine. Smaller autumn. Routine seed sowing and pricking Thus the management of a cold green­ in detail on pages 70-71. The following pages pots are best plunged in peat or sand. off into flats or pans is all that annuals and house is an amalgam of attention to ventila­ also detail the cultivation of fruits and other Winter sets limitations on what can be biennials initially require (see pages 55-56). tion, atmospheric moisture, warmth and salad and vegetables. Another aspect of grown permanently in the unheated green­ Thereafter place the young plants singly into light. Holding the environmental balance is a garden food production that a greenhouse house. From about mid-spring to late autumn 5 in pots, or space three out into 6 or 7 in con­ complicated art in which experience is an can assist is the raising of seedlings for trans­ the full range of cool greenhouse plants thrive tainers. A fairly rich soil mix is recom­ important factor. planting outdoors. This frees the gardener happily. From late spring to early or mid- mended, a John Innes potting No. 2 being from dependence on commercially raised autumn even warm greenhouse plants suc­ very satisfactory. Once the young plants are Plants for the cold greenhouse plants, and makes the growing of unusual ceed. With a heated propagating case, such 3-4 in tall, pinch out their tips to encourage Most annuals, biennials and shrubs, provided vegetables, and the obscurer varieties of plants can be over-wintered. branching and a more bushy habit. As soon they are hardy, can be successfully over­ common ones, possible. As with flowers, the as they are growing more strongly, in late wintered in a cold house. The advantage of quality of crops grown under glass will be Flowering plants from seed winter or early spring, commence liquid doing so is that they flower two to three weeks higher than those grown outdoors, due to A wide range of hardy and tender annuals feeding and repeat at 10-14 day intervals. earlier than plants grown outdoors. Their the lack of weather damage. This is especially and biennials is readily available to provide At about this time, insert twiggy sticks or condition, not having had to contend with true of salad crops and strawberries. color and interest in the cold greenhouse canes for support. For full details, see page 55.

July August September October November December Harvest sweet peppers, lettuce, Sow lettuce, radishes, mustard and Sow lettuce, radishes, mustard and Sow lettuce for crops in spring. Sow onions for transplanting. Harvest chicory. radishes, mustard and cress, cress, winter endive. cress, alpine strawberries. Plant fruit trees. Box up rhubarb crowns, chicory Bring in remaining plunged bulbs parsley, tomatoes left in the Sow cyclamen seeds. Take fuchsia Plant late in month: apricots, Continue to pot up and blanch and remaining seakale. Insulate for spring flowering. greenhouse. cuttings, pot on half-ripe cuttings. peaches, grape vines. seakale. boxes if necessary. Take advantage of quiet period to Take hydrangea cuttings. Harvest lettuces, parsley, radishes, Bring in tender bedding perennials Bring in pots of herbs for winter do cleaning and maintenance jobs Take half-ripe cuttings. mustard and cress. for over-wintering. supply. on greenhouse and equipment. Lift seakale roots late in month, Repeat sowings of annuals. Prick Plant grape vines. pot up and blanch. out annuals sown in September. Cut back chrysanthemums to 6 in Sow hardy annuals for spring Pot on biennials. Sow sweet peas. after flowering to encourage flowering under glass. Over-winter chrysanthemum stools growth for cuttings. Prick out Pot on hardy biennials for spring and dahlia tubers. October-sown sweet peas. Pot on flowering. annuals. Bring plunged bulbs into Bring in evergreen azaleas, pot- the greenhouse as shoots appear. grown chrysanthemums. Plant bulbous irises and hyacinths in pots. Fruits

A told greenhouse can be used to grow a to give plants the maximum possible light. It Melons variety of fruit (Tops, the best choke being will be difficult for plants to thrive, and for melons, strawberries, grapes, peaches, apri- fruit to ripen, if plants in pots are shaded b) cots and nectarines. The more stable environ­ a thick vine or a vigorous peach. ment of the greenhouse, and the protection Training and support Except for strawberries it affords, allows the production of earlier, all the types of fruit suggested for the cold more reliable fruit crops compared with out­ greenhouse will need some system of wire; door culture, especially in districts with on which they can be trained and this should cooler than average summer temperatures. be combined with a support system. Always The greatest limitation of the cold green­ remember to arrange the training system house for growing fruit is that many of the before planting because inserting wires be­ crops, but particularly grapes, peaches, apri­ hind growing plants is not only difficult but cots and nectarines, take up a great deal of can lead to damage. space. If possible, it may be best to devote a whole greenhouse to fruit culture but if this Ventilation is not practical, select fruit that will not The exact needs of fruit crops vary in detail occupy the whole house or block light from but good ventilation is essential. Peaches, for other plants. Alternatively, cultivate plants example, ideally need ventilation from the in pots to restrict their growth to manageable roof and sides of the house. When growing a proportions. crop that takes up a good deal of space in the greenhouse always make sure that the Choosing a greenhouse growth of the plant does not interfere with 1 Prepare a soil mix of 2 oz steamed 2 Stretch wires along the sides 1 ft apart I or small-growing crops such as melons and the ventilation system or make window; bonemeal and 2 oz compound fertilizer to and 15 in from the glass. Tie in two canes strawberries a house of conventional dimen­ difficult to open. one 2 gal bucketful of soil. Place this on top per plant, one from soil to eaves, the other sions will be suitable but a larger house is For full details of cultural practices see the of the border soil in a ridge 1 ft high. from the eaves to the house ridge. In May necessary to accommodate other fruit ade­ volume Fruit in this series. plant the seedlings raised in heat. quately unless they are grown in pots. When choosing a greenhouse for growing fruit CULTIVATION remember that a vigorous grape vine will need a border at least 8 ft long and that a Grapes Construct a training system of peach, apricot or nectarine will require a horizontal wires 9 in apart and 15 in from greenhouse with a wall or glass sides at least the glass. Plant in November in well- 12 ft high. When selecting a greenhouse for drained porous border soil containing fruit growing follow all the general principles loam, peat and grit with added base described on pages 12-13. Fruit trees should fertilizer and limestone. Water to give a be grown against a south-facing wall. thorough soaking in early spring. Mulch. Keep the soil thoroughly damp, watering Planting every 7-10 days in hot weather, and re­ Vines, peaches and their relations and melons duce watering as fruit ripens. Ventilate can all be planted direct into the border soil from January to March then close the of the greenhouse, which should be prepared vents until May or when the air tempera­ according to the individual requirements of ture exceeds 18°C/64°F. each crop. Strawberries, however, are best Peaches, apricots and nectarines Con­ cultivated in pots or barrels. If space is struct a training system of wires placed limited it is also possible to cultivate grapes, 10 in apart and 10 in from the glass. Plant peaches, apricots and nectarines—and even in October in border soil enriched with plums, apples, pears and cherries—in pots, peat and add lime at 1 lb per sq yd. Mulch. although for the last four of these it is essen­ Water well after planting and from the 3 As the plants grows tie stems to canes 4 Thin the fruit to four of the same size per tial to select varieties grown on dwarfing time growth starts. Ventilate during the and laterals to the horizontal wires. Pinch plant when fruits are walnut-sized. Water rootstocks. Container culture has the added day only after fruit has set. Close the house out the growing point when plant is 6 ft the plants very well and liquid feed them advantage that it is possible to provide at night. tall. Pinch back side shoots to two leaves every 7-10 days. As fruits enlarge support exactly the right type of soil but it is important beyond each flower. Increase ventilation. them with netting slings. Tomatoes 1

Tomatoes are an excellent choice of crop for Pricking out When the seedlings have de­ growing bags or straw bales (for full details roof at one end and to the stem of the plant, a cold greenhouse for they are tender plants veloped their first true leaves 10-12 days after see page 46). If plants are to be grown directly under the lowest true leaf, at the other, Each that profit greatly from the protection glass sowing, carefully prick them out singly into in greenhouse soil, double dig and enrich plant is then twisted loosely round the string affords. A heated propagating case can be individual 3 in peat or plastic pots filled with a the lower spade depth with well-rotted com­ as it grows. Take care not to damage the plant used in a cold greenhouse to provide the proprietary potting soil or mix. Insert a small post or manure. For pot or ring culture fill pots stem by pulling the string too tight. Alter added heat necessary for raising plants from dibble beneath the roots of each seedling and with John Innes No. 2 or 3 or an equivalent natively, plants in pots or grown entirely in seed. All greenhouse-grown tomatoes need hold the seedling by its leaves to prevent mix. Plant tomatoes when the young plants greenhouse soil may be loosely tied to careful attention to watering, feeding and damage. Use the dibble to make a hole big are 6 to 9 in tall. This is usually when the bamboo canes for support. care in controlling pests and diseases. enough to take each seedling without re­ flowers on the first truss are just opening. stricting its roots. Water the seedlings gently Immediately before planting, water plants Watering and feeding Raising tomato plants to firm the soil round their roots and replace thoroughly and destroy any plants that show The success of greenhouse-grown tomatoes Without the use of a heated propagating case them in the propagator. signs of disease. Make a hole in the chosen depends on meticulous attention to watering it is usually best to purchase tomato plants Temperature control Keep the seedlings at growing medium big enough to accom­ and feeding throughout the life of the plant. rather than raise them from seed. Choose 18°C/65°F until they begin to shade each modate the roots without crowding. Place Plants will be damaged by drying out which strong plants with no trace of disease. other, then turn the thermostat down to the top of each rootball level with the soil causes flower drop, or waterlogging which is Seed sowing Seed may be sown in a heated 16°C/60°F. About a week before planting, surface. Plants raised in peat pots should be a particular hazard for plants grown in iso­ propagating case in early January for plant­ reduce the temperature to 10°C/50°F. Apply made thoroughly wet before planting (tear lated systems such as growing bags, for it ing eight weeks later. Sow seed thinly in a balanced liquid feed (see page 41) and sup­ down one side of the pot wall if necessary to quickly kills off plant roots. Plants in growing John Innes No. 1 compost placed directly in port plants with a small cane if they become prevent drying out) and planted complete bags will only thrive if the growing medium is the case or in flats or pans which are placed too tall to support themselves. with the pot. Space plants about 18 in apart kept uniformly moist, which may mean water­ in it. Seeds sown too thickly are likely to each way. Give planted tomatoes a thorough ing three or four times a day in hot weather. suffer from damping-off diseases. Set the Planting watering in and keep them moist to make Ring culture also demands much water be­ propagator thermostat to 18°C/65°F. At this While seedlings are maturing, decide which sure the roots become well established. cause drainage is very rapid. The most stable temperature germination and emergence growing system will be used. The main choices Support In the greenhouse tomato plants are water supply is achieved with plants grown should take place in 7-10 days. Keep the are between greenhouse soil, ring culture, usually best supported on soft garden string directly in greenhouse soil. In all systems, seedlings evenly moist but not waterlogged. 9 in pots placed direct on greenhouse soil, tied to a horizontal wire near the greenhouse irregular watering will cause fruit to split.

Raising from seed Planting

1 Early January Sow 2-3 seeds per sq in 2 Prick out seedlings 10-12 days after 3 Place pots in propagator and set 4 Mid-late April When flowers on first in propagator filled with sieved soil. sowing using a small dibble. Transfer to thermostat to 18°C/65°F. Water sparingly truss are just opening water plants well. Sprinkle over 1/8 in layer of soil and 3 in pots filled with John Innes No. 1 or but often. Liquid feed before planting. Remove plants from pots and place 18 in cover with newspaper. an equivalent mix. apart in chosen growing medium. Tomatoes 2

Greenhouse grown tomatoes should he Pollination and fruit setting Support liquid fed with a proprietary fertilizer mixed If fruit setting is a problem it can be improved with the water according to the manufac­ by assisting pollen dispersal. Spray the plant turer's instructions. A balanced fertilizer will with a fine droplet spray, shake the plant provide nitrogen to encourage vegetative gently or tap the flower trusses. growth and potassium to improve quality. Stopping Trimming and de-leafing In a cold greenhouse tomatoes will not As tomato plants grow they develop side usually produce more than six or seven fruit shoots in the junctions (axils) between leaf trusses per season so it is best to snap off the and stem. These must be removed while they growing point two leaves beyond the sixth are small or they will use up water and or seventh truss. Continue to remove further nutrients needed by the productive parts of sideshoots, which will often be stimulated the plant. Snap off each side shoot cleanly into growth by the stopping process. between finger and thumb, preferably in early morning when the plants are turgid. Avoid Harvesting pulling which leaves scars that are easily Ripe fruit should be ready for picking in mid- invaded by disease-causing fungi. May from seed sown in early January. Harvest When plants are 4—5 ft tall, remove the time depends upon sowing time. If climate lower leaves up to the first truss. Use a sharp allows, crops can for instance be sown in knife and cut cleanly leaving no snags. De- |une for September-December crops. leafing allows more light to reach the plant 1 Bamboo canes can be 2 Snap off side and basal 3 Spray the flowers with a base, improves air circulation and helps to Pests and diseases used for support. Tie the shoots between thumb and fine droplet spray or shake combat fungal diseases. As the trusses crop Greenhouse tomatoes are notoriously sus­ plant on loosely with soft forefinger. If possible de- the plant gently to disperse make sure any yellowing or diseased leaves ceptible to pests and diseases which are garden string so that stems shoot in early morning pollen and improve fruit are removed. described in detail on pages 38-40. are not damaged. when the stems are turgid. setting.

TRAINING SYSTEMS Stopping

Vertical training Plants are carefully V-training Plants are twisted round strings 4 Liquid feed growing 5 Snap off growing point 6 Pick ripe fruit by snap­ twisted round soft string attached below set alternately at 60° to the ground. This plants following manu­ 2 leaves above top truss ping the stalk, leaving the lowest true leaf and to a horizontal wire system is good for straw bale culture with facturer's instructions. when 6-7 trusses have set calyx on the fruit. Ripe fruit 6-8ft above ground level. plants placed closer than 18 in. Water them as necessary. fruit. Remove any lower left under hot sun will soon leaves that turn yellow. lose its firmness. Vegetables and salads 1

The greatest advantage of the cold green­ Leaf crops Winter endive Sow seed as for lettuce in such protection include parsley, chives, mint, house in salad and vegetable growing is that Good choices for the cold house include salad late August to early September and put in a French tarragon, pot marjoram, rosemary, it can be used to extend the growing season greens, seakale and herbs. well-lit position. Ventilate the house and thyme and sage. Water plants well and venti­ at both ends of the year. In warmer parts of Lettuce Sow lettuce seed in pots then prick water the seedlings regularly. When plants late the house during the day in all but the the country, an unheated greenhouse can them out into peat blocks or pots before are fully grown, tie them round loosely with worst weather. In spring, begin sowing seeds also provide winter crops. Those summer planting them in greenhouse soil. If seed is raffia and place a large plastic pot over of annual and biennial herbs as soon as the crops normally grown outside, such as tomato sown in small quantities at fortnightly inter­ selected plants to blanch the leaves. Cover greenhouse temperature is high enough. and cucumber, can be grown under glass for vals from early spring until autumn, a the drainage hole of the pot and support it faster maturing and protection against rain, constant supply can be assured. To prevent on crocks to allow free air circulation. Root crops and bulbs hail and wind. With good planning a green­ diseases, particularly botrytis, it is important Seakale From late September to late Small quantities of root crops can be raised in house can provide food for the kitchen to ventilate the house well in all but the worst October, lift seakale crowns from the garden the cold house for harvesting weeks before almost all the year round. It is also very weather. The crop needs adequate light and and trim off the side roots and any yellowing the main outdoor crops. Seed sowing can useful for raising young vegetable plants attention to watering. Give a few thorough foliage. Trim the main roots to about 6 in. begin in February-March in peat pots or which are later planted out into the garden. waterings rather than many small ones. The Allowing 3 crowns per pot, plant the crowns directly into slightly acid greenhouse border The most significant limitation of the cold crop will be improved by a thorough soaking in 9 in plastic pots filled with rich soil mix soil prepared according to crop requirements. house is implicit in its description—because about 10 days before harvesting. such as John Innes No. 3. Cover each pot with If the vegetables are to be eaten really young it is unheated, the gardener must wait until Mustard and cress As long as the greenhouse another of the same size turned upside down and tender, make more sowings at three or the house temperature reaches a suitable temperature is 10°C/50°F or above, mustard and place under the greenhouse staging. four week intervals. Thoroughly water and point before certain seeds can be sown. and cress can be sown at weekly intervals. Ideally the crowns need a temperature of well ventilate the house once the tempera­ Also, the winter temperature in the cold Sow seed on a moist tissue in a shallow dish about 10°C/50°F, so if the house gets too cold tures begin to rise in April. house precludes the growing of many out of and place it in the dark under a bench, lightly insulate the pots with newspaper or burlap. season crops. When considering which crops covered with a dark cloth or newspaper if Herbs Many herbs will continue growing Pods to grow, make maximum use of space. Catch necessary to exclude light. Once the seeds through the winter if plants are potted up and Select dwarf varieties of bush beans for cold crops such as carrots and radishes can be have germinated, move the dish up into a brought into the cold house for protection greenhouse cultivation and make two sow­ grown between tall crops before they develop. lighter place and keep the seeds well watered. during winter. Herbs that benefit most from ings, one in spring for early summer cropping,

Lettuces

1 Sow seed in 31/2 in pots filled with potting 2 Prick out as many seedlings as required 3 When plants have 4-5 true leaves plant 4 Harvest lettuce by carefully pulling up soil. Cover the seeds lightly and water into small individual peat blocks or pots. the peat blocks or pots 8 in apart into whole plants and trimming off the roots, using a fine rose. Repeat sowings every Water well and increase the ventilation the greenhouse border soil. Water well or cut plants below lower leaves. Remove 2 weeks. according to the weather. and ensure good ventilation. discarded matter from greenhouse. Vegetables and salads 2 the other in July for autumn harvesting. Pre- late the house in warm weather. Watch WITLOOF CHICORY germinate the seeds and sow four or five for aphids and red spider mites. Spray with seeds round the edges of a pot filled with John malathion or derris if pests are seen. Innes No. 2 or equivalent mix. For the spring Eggplants These need very similar cultural sowing wait until early April in cool areas, or conditions to peppers, and plants can be germinate the seeds indoors. Water the raised from seed in the same way or pur­ plants well once flowers appear and ventilate chased from a nursery. Aim for planting in the house in warm weather. early May and allow two plants to a standard size growing bag. Pinch out the growing Vegetable fruits points when plants are 9-12 in high and Cucumbers, sweet peppers and eggplants, allow only 5 or 6 fruit to develop on each as well as tomatoes whose culture is des­ plant. Remove any extra fruits, leaving the cribed in detail on pages 70-71, can all be remaining ones well spaced, and pinch off grown in the cold greenhouse. any extra flowers that form. Water and feed Cucumbers Pre-germinate cucumber seeds often but sparingly and ventilate the house in then sow them singly in 3 in pots filled with hot weather. Watch out for pests and spray |ohn Innes No. 1 or a similar mix. Allow against those that appear as for peppers. 4 to 5 weeks from sowing to planting and In November, lift witloof chicory roots plant 3 or 4 chicory roots at weekly time the operation so that planting can take Raising seed from the garden and cut off the leaves to intervals in a 9 in plastic pot filled with place in late May, if necessary germinating Seeds of many vegetables can be raised in within \ in of the crown. Trim the roots to sand so that each crown is 1/2 in above the the seeds indoors. Preferably, plants should the cold house for planting out once the 9 in and take off any side shoots. Store the top of the soil. Water sparingly and cover be planted in growing bags (2 plants per weather is suitable to provide earlier, more roots horizontally in boxes of dry sand with pot to keep out light. Place under standard bag) or singly on straw bales. At reliable crops. Sow seed in peat blocks or outside under a north wall until they are the bench and keep well ventilated. The planting time or before, erect a system of pots for easy planting later on and keep needed. From mid-November onwards chicons will be ready after 4 weeks. supporting strings tied to horizontal wires house well ventilated. See pages 55-6. near the greenhouse roof, or insert bamboo canes on to which plants can be loosely tied. Cucumbers Developing plants should be well watered and given liquid feed and the atmosphere in the house should be kept as humid as pos­ sible. Pinch and trim the plants as shown in the illustrations and remove any male flower. Sweet peppers These vegetable fruits are best grown in the cold greenhouse in pots. Because the seed needs a temperature of 21°C/70°F for germination, seeds must be germinated in a propagating case and the seedlings hardened off, or the gardener can buy plants from a nursery. Allow 10 to 12 weeks between sowing and planting in late May. Sow seed thinly on moistened soil covered with 1/8 in of compost and then with glass and newspaper. When seedlings are large enough to handle, prick them out into 3 in pots filled with John Innes No. 3 compost or plant 3 plants in a standard sized growing bag. Place pots 18 in apart on the border soil or greenhouse staging. When plants are about 6 in tall, remove the growing point to 1 Late May Plant seedlings raised in heat in 2 June-July Tie growing plants to canes for 3 June onwards Keep single laterals in each encourage bushy growth, and support and 9 in pots filled with potting soil. Water support. Pinch out growing points as main leaf axil and stop them at 2 leaves. Remove tie them to bamboo canes if necessary. Keep and liquid feed regularly. Keep the stems reach the roof. Ventilate frequently, male flowers if appropriate. Harvest by plants well watered and liquid fed and venti­ greenhouse humid. but carefully, as humidity is important. cutting the stems with a sharp knife. The year in a cool greenhouse 1

A cool greenhouse, one provided with a heat­ To many gardeners, the cool greenhouse with are the many house plants available, and which burn gas or oil, can harm plants if ing system that ensures that temperatures do is the norm and a cold or warm house is a sub-tropical flowering plants such as those they are not adjusted correctly. Badly set not fall below 4.5°C/40°F, provides an en­ deviation from it. When gardening literature fostered by Victorian conservatory gardeners wicks and burners can cause the heater to vironment suitable for a vast range of plants. and catalogs are consulted, it will be noticed for winter blooms. give off poisonous fumes. Nearly all the plants from the world's tem­ that "greenhouse plants" tends to mean Thermostats The sensible management of a perate zones can be cultivated, and the those to be grown in a cool house. Management heating system centers around the use of choice extends into those from the sub­ While there are very many plants to choose The principles of cool greenhouse care are thermostats. These devices sense tempera tropical and tropical regions. A distinction is from for growing in a cold house, it is often those outlined earlier in this book for the ture changes and act as switches, turning the made between those plants that can be worth experimenting to try to widen the running of any greenhouse. The one main heating system on and off as required. They grown in winter in a cool house, such as range still further. Plants rarely have an difference in the running of a cool house is are most often used with electrical systems, salads and chrysanthemums, and those such absolute minimum temperature which kills the need to manipulate the heating system. which are easily controllable and capable "I as sub-tropical bedding plants which are them, unless it be frost level which, by An inefficient heating system is undesirable producing heat quickly. Gas and oil systems dormant at cool greenhouse temperatures freezing the cells, can cause physical damage. for three reasons. First, if the system is not can also be fitted with thermostats—as are but survive the winter undamaged, when Many plants thought to need higher tem­ running correctly it will not be able to main­ domestic central heating boilers. they would die in the open garden or an peratures than the cool house minimum can tain the necessary temperature and plants A thermostat is only useful if the system it unheated house. In addition, all those plants in fact be acclimated to the prevailing con­ will suffer. The second reason is that in­ controls has sufficient capacity. The heaters which will tolerate cold greenhouse condi­ ditions. A lot depends upon avoiding ex­ efficiency in the use of fuel will lead to must be capable of maintaining the desired tions can be grown in a cool house. In many tremes and sudden changes. If the balance rapidly escalating bills. Heating a greenhouse temperature without running constantly. The cases their growing seasons will be longer. It of the environment—heat, humidity and is expensive, and if the system used keeps section on heating (pages 18-23) shows how is possible to raise a wider range of out-of- ventilation—is carefully watched, plants the temperature unnecessarily high, or burns to calculate the size of heating installation season food crops and ornamentals given the thought tender may survive and go on to fuel inefficiently, the cost will be magnified. necessary. Once a large enough system has minimum temperature of a cool house. flourish. Among those worth experimenting Third, certain kinds of heating system, those been installed, thermostatic control will

January February March April May June Check draft-proofing, insulation Ventilate when possible and Increase watering, ventilate well on Pay attention to ventilation and Water freely, shade as necessary in Turn off and overhaul heating (if fitted) and heating system. Set gradually increase watering. Day sunny days and maintain a more watering as temperatures increase. sunny weather and encourage a system. Ventilate freely, shade thermostats to night minimum of length will increase. Maintain humid atmosphere. Be alert for and Keep heating switched on, setting more humid atmosphere. whenever necessary and damp 4.5°C/40°F. Water plants in flower, minimum temperature. combat insect pests such as aphids. thermostat for minimum night Sow cineraria, primula. Plant down and spray to raise humidity. water others sparingly. Maintain a Sow bedding plants with long Sow sweet pepper, squash, half- temperature. chrysanthemums and move Water as required, twice a day if dry atmosphere to discourage germination/growing periods, half- hardy annuals, tomato, bedding Sow cucumbers, squashes, outside. Pot on carnations, zonal necessary. mildew. hardy annuals, sweet peas, begonia, plants, basil. pumpkins, dwarf French beans, pelargoniums, tuberous begonias, Sow calceolaria, Primula nialamides, Sow canna, fuchsia, pelargonium. calceolaria, salvia, schizanthus, and Transplant rooted cuttings taken in runner beans for transplanting annuals raised from spring-sown zinnia, all for autumn and winter Bring in bulbs for flowering as they germinate in a propagating case. winter. outdoors, primulas, half-hardy seed. Feed all plants in active flowering. show growth. Continue to take chrysanthemum Repot orchids and other perennials annuals such as stocks and zinnias, growth. Take precautions against Feed tomato plants and all other Take cuttings of winter-flowering cuttings. as necessary. and Campanula pyramidalis. insect pests. plants in growth. Pot on plants chrysanthemums and carnations. Sow brassicas and onions for Begin to take softwood cuttings. Continue re-potting and potting on. Pinch out young fuchsias when raised from seed as necessary. transplanting outdoors. Sow early Pot up tuberous begonias. Move bulbs which have flowered 4-5 in high. Plant out bedding plants into their bunching turnips, carrots, parsnips, to a frame. Move over-wintering Remove cucumber laterals and all flowering positions in the open beets, okra, tomatoes, cucumbers. pot plants outdoors into a male flowers. garden. Plant tomato plants from middle sheltered position. Tie in tomato plants and pinch out Plunge azaleas, hydrangeas and of the month. Transplant seedlings from seed side shoots. other pot plants which have Begin re-potting of ferns and palms. sown earlier in the spring. Take finished flowering. Bring in more bulbs for flowering. further softwood cuttings. Cut back shoots of regal Dust tomato flowers to encourage pelargoniums. pollination. Move half-hardy plants into a frame to harden off. The year in a cool greenhouse 2

ensure that it only operates when the tern humidity by regular damping down and the sun heat is thus needed to raise the tem­ be grown in a cool greenhouse. The plants perature falls below the pre-set level. The installation of damp sand beds under benches. perature to unwanted levels. chosen, especially those illustrated in the heater will raise the temperature, triggering While summer heat and winter cold have step-by-step sequences, are the most re­ the thermostat again and cutting off the to be countered by active management, the Growing plants warding for the relatively inexperienced and/ system. Thermostats must be placed away most difficult times of the year for the running The following pages deal with the cultivation or those which illustrate a key growing prin­ from drafts and cold spots, where they will of the cold greenhouse can be spring and of ornamentals, including bedding plants ciple. The information given can be adapted give an artificial reading. autumn. During these seasons the sun has which are covered in detail, and food crops. to cover the cultivation of many other plants. Balance While the main stress of cold green­ power to quickly heat the greenhouse, while All the ornamentals and food crops covered There are other categories of plants of house management is on maintaining the the nights are cool. Cold daytime tempera­ in the preceding cold greenhouse section, interest which are less popular but still worth winter minimum, thought must be given to tures can easily occur due to sudden weather such as annuals, tomatoes and salad crops, considering if greenhouse space is available. the other components of greenhouse changes. This combination can be particularly can be added to the list. The difference comes For example, many shrubs can be grown in management. Shading, ventilation and humi­ trying in the late winter and early spring. Sun mainly in timing of sowing and cropping. containers under glass and brought into dity control are all crucial, especially in heat is becoming more powerful, and the Tomatoes, for instance, can be planted from flower earlier than outside. Examples are summer. Just as plants have a minimum effect of the sun combined with artificial mid-February onwards in a cool greenhouse, lilac, forsythia and hydrangea. Fruits such as temperature for healthy growth, so they have heating can quickly raise the temperature, while in a cold house late April is the earliest citrus can be grown in tubs in cool green­ maximum levels of temperature which will often above the level required, unless ventila­ possible date. Annuals will flower earlier in house conditions. Most citrus trees will harm them. Problems caused by high air tion is promptly given. Under these con­ the spring in a cool house than in a cold one. tolerate a winter minimum of 7°C/45°F, temperatures are often magnified by failure ditions automatic ventilators (see pages 15- Lettuce, radish and other salad crops can be though the lime needs 10°C/50°F. Summer to ensure adequate humidity. If there is not 16) show their worth. A cold house will not sown in late summer and autumn for autumn temperatures should be maintained at 13°- enough water vapor in the atmosphere, suffer so much from this problem because it and winter cropping. 16°C/550-61°F for successful cropping. Full plants will transpire—give out water from does not have the reservoir of artificially Other plants Many more plants than those details of the cultivation of warm temperate their leaves into the air—too quickly. Increase generated heat that a cool house has. More described in detail on the following pages can fruits are given in Fruit in this series.

July August September October November December Maintain a moist atmosphere and Continue summer shading, Reduce watering and damping Switch on the heating system and Maintain minimum winter Fit insulation to greenhouse sides if attend to watering. Ventilate well watering and damping down down as temperatures drop. set the thermostat to maintain a temperature as October and possible and stop up all drafts. and shade as required. Sow regime. Watch for cool nights Restart the heating system to minimum night temperature of ventilate sparingly. Further reduce Cover the house with burlap or sapiglossis and make a repeat towards the end of the month as check it and switch on if necessary 4.5°C/40°F. Ventilate freely on watering of all except plants in mats in very severe weather. sowing of Primula malacoides days shorten. towards the end of the month. warm days but exclude fog and flower. Protect tender plants with paper, and calceolaria. Sow annuals for spring flowering, Check winter fuel supplies if damp. Reduce watering and Pot on annuals. Keep in good light polyethylene or burlap if severe Take hydrangea cuttings. cyclamen, cineraria. necessary. Reduce shading. remove shading completely. and give minimum water. frost is forecast. Cut watering to Stake plants, especially annuals Prick out calceolarias and other Sow more annuals for spring Pot up the last of the bulbs. Bring in the first batch of bulbs for the minimum. growing in pots, and train climbers seedlings from earlier sowings. flowering. Feed cyclamen, cinerarias, primulas winter flowering. Ventilate a little when possible and Pot on pelargoniums reared from Take cuttings of pelargoniums. Pot up remaining bulbs. and camellias. Prune shrubs. run a fan heater to circulate the spring cuttings and plunge Pot on primulas, cinerarias. Bring in azaleas, camellias, If possible, remove all plants and Sow lettuce. atmosphere. outdoors. Pot on carnations, and Plant bulbs for winter and spring chrysanthemums and other pot fumigate the house against fungal Bring in fuchsias, begonias and Bring in more bulbs. repot freesias. flowering, such as freesias, tulip, plants that have spent the summer diseases. hydrangeas and store under the Box up seakale and witloof chicory hyacinth, narcissi. in the open. Scatter pellets to combat slugs. staging. Keep almost dry. for forcing. Feed chrysanthemums standing Pot on cyclamen, cinerarias and Cut down chrysanthemums after outdoors and water well. primulas into final pots and move they have flowered and start to Repair any structural damage to onto greenhouse shelves. take cuttings of soft growth. the greenhouse and repaint if Take cuttings of bedding plants Keep cineraria, cyclamen, primulas necessary. before they are discarded, and of and other plants required for coleus, heliotropes and fuchsias. Christmas flowering in a warm part of the house. Water them with care, avoiding the foliage. Clear debris, dead leaves and used pots from the greenhouse. Clean all pots, trays and propagating equipment. Bedding plants 1

The cool greenhouse is an ideal place for the artificial heat provided by the cool without the addition of sand. The larger important until after germination. raising summer bedding plants. Using the greenhouse, development of seeds sown in seeds, such as those of zinnias—and small As soon as the seeds germinate (this may greenhouse in this way shortens the pro­ the first two months of the year is slow seeds that have been pelleted—are best take one to three weeks depending on pagation period and, as long as plants are because of low winter light intensity. planted singly by hand. Cover sown seed temperature and the species) remove any properly hardened off and precautions taken Seeds of bedding plants may be sown in with soil but be careful not to make this covering and put the containers in a well lit against disease, ensures the production of flats or pans (dwarf pots). Fill the chosen covering layer too thick. Label the con­ place but be careful that they do not risk sturdy plants. The other advantages to the containers with a good seed-growing mix­ tainer clearly then water in the seeds with a being scorched by strong sunlight. Water gardener of raising his own plants from seed ture which should be damp. There is no need dilute mixture of Captan or a copper-based with dilute Captan to combat damping oil compared with buying plants direct from the to avoid peat-based soils, with their low fungicide to help prevent damping off disease. and other seedling diseases. If possible nursery are that he knows exactly what he is nutrient reserves, because the seeds will Use a rose on the watering can so that seeds maintain the temperature at 21*C/70*F to growing and that there is less risk of plants germinate relatively rapidly in the frost-free are not dislodged from their planting promote speedy development. The seedling) being damaged as they do not have to be environment of the greenhouse. Once the positions by the water. also need good ventilation and the green transplanted from overcrowded seed flats. containers are full, press down the soil with house ventilators should be opened for at the fingers or a presser board to within 1/4 in Germination least an hour a day except in very severe- Seed sowing of the top, but be careful not to press too Even in a cool greenhouse, developing seeds, weather conditions. One of the most critical aspects of raising hard as this will restrict the drainage and particularly those sown in mid-winter, will bedding plants from seed in the greenhouse tend to encourage damping off diseases and benefit from extra warmth. This is best pro­ Pricking out is timing. As a general rule, the sequence of attack by sciarid flies. vided by a propagating case. When using Seedlings should be pricked out as soon as sowing is determined by the speed at which The best method of sowing seed depends such a case, place the seed containers in­ they are large enough to handle. If left in seeds germinate and by the growth rate of on the size of individual seeds. For small seeds side it and set the thermostat to 21°C/71°F. their original containers they will become the developing seedlings. For this reason such as those of Begonia semperflorens, mix If a propagating case is not available, either overcrowded and their roots will become so slow-growing species required for summer the seeds with fine dry sand in the seed packet take the seed containers indoors and put entangled that the gardener will be unable to bedding are sown in February and March then sow them by broadcasting, keeping the them in a warm place or cover them with avoid damaging them when they are re­ and a monthly sowing plan adopted accord­ hand close to the soil surface. Larger seeds a sheet of glass. A piece of newspaper may moved. Prick out seedlings into individual ing to the scheme shown above. Even with can be broadcast in the same way, but be placed on top of the glass as light is not pots or flats filled with John Innes No. 1 or a

Growing bedding plants from seed

1 Fill a seed flat with seed-sowing soil. 2 Sow the seeds thinly. Small seeds can 3 Sieve soil over medium-sized or large 4 Water the seed flat with a dilute mixture Firm the soil with the fingertips or a be mixed with fine dry sand and broadcast seeds so that they are just covered. Do of Captan or other fungicide to combat presser board to within 1/2 in of the top. onto the soil to make sowing easier. not cover small seeds. damping off and other diseases. Bedding plants 2

similar potting soil, taking care to handle Propagation then) by one leaf and between finger and While most bedding plants are raised from PEAT BLOCKS PLANTING OUT thumb. Use a dibble to pry out the seed­ seed, several important plants can be propa­ lings and to make a hole in the soil big gated by cuttings or division. Full details of enough to accommodate each plant. If seed­ these methods of propagation are given on lings are pricked out into flats, allow at least pages 57-63. 11/2 in between them each way to prevent Cuttings can be taken in autumn when overcrowding. Firm the soil round each the plants are lifted, or in spring from tubers seedling with the dibble, label and give kept dormant over the winter. Geraniums are another watering with dilute fungicide to one of many bedding plants that can be guard against damping off. propagated by cuttings. Keep the cuttings at Even in ideal conditions the seedlings will a minimum temperature of 4°C/40°F over suffer some check to their growth after winter, and water sparingly. Pot on as neces­ Larger seeds can be sown in peat blocks When seedlings are ready to be planted pricking out but careful handling and trans­ sary into 4 or 5 in pots, harden off and plant formed from damp peat-based soil with out and have been hardened off in a frame planting when the root system is small and out in the normal way. a blocking device, or in peat pots. Both or been placed outside during the day, unbranched will help to reduce this to a have the advantage of being planted plant in the flowering positions. If possible, minimum. After pricking out the temperature Overwintering with the young plant in the flowering remove both plants and soil, allowing can be reduced to 18°C/65°F but good venti­ Some bedding plants can be overwintered in position. The seedlings are therefore not the roots to be gently teased out and the lation is still essential to healthy seedling a cool house for re-use the next season. Lift subject to the disturbance of pricking out. young plants to be inserted with an development. When seedlings are big enough the plants in autumn and pot or box up. Cut Sow 2-3 seeds in each block and water adequate rootball. Make planting holes and when there is no chance of frost, seed­ back the foliage by about one-half, water well. Provide the conditions described in with a trowel and water well after firming lings should be hardened off in a cold frame very sparingly and ventilate freely to guard the caption sequence below. When the in. Water well until the plants have be­ (see page 91) or by turning off the greenhouse against gray mold. Plenty of light is neces­ seedlings have reached first true leaf come established. Pot-grown greenhouse heating system and gradually increasing the sary to avoid the production of drawn, weak stage, thin to the strongest per block. perennials can be used as dot plants. ventilation first by day and then at night. growth. Plant out as normal in spring.

5 Place the flat in a propagating case at 6 As soon as the first seedlings emerge, 7 Spray seedlings with Captan or another 8 Prick out seedlings into flats, boxes or 21°C/70°F, or in a warm place indoors if a place the flat in good light. Keep the dilute fungicide to combat damping off individual pots as soon as they are large case is not available. temperature at 21°C/70°F. disease. Ensure that ventilation is adequate. enough to handle. Fruits and vegetables 1

The cool greenhouse can be used to best not open the ventilators until the temperature Early strawberries effect in growing food crops if it is used to reaches 24°C/75°F. As the flowers open, cultivate not only tomatoes, cucumbers and carry out a daily pollination routine, trans­ the other vegetable fruits described on ferring pollen from flower to flower with a pages 70-73 but also more tender vegetables small paint brush. During this pollination such as okra. Melons and early strawberries period do not damp down the house as this are also good subjects for the cool house and may prevent fruit from forming. To obtain so, if space allows, are peaches and nec­ fewer, but larger fruit, remove the smallest tarines which often fail to do well in the open. flowers as soon as their petals have fallen off and leave eight to ten fruits on each plant. Early strawberries Once fruit begins to set, resume the The cool house will enable the gardener to damping down routine and water the plants pick crops of strawberries in March or April. very well in sunny weather. Continue feeding Propagation In late June, peg down the until the fruits begin to turn pink in order to runners of plants growing in the open garden improve fruit flavor. into 3 in pots filled with John Innes No. 1 potting compost buried with their rims level Melons with the soil surface. After four to six weeks, In the cool house, melons can be cultivated when the new plants are well established, as described for the cold house on page 69 sever them from the parents and place the except that by maintaining a minimum pots on well-drained soil or in an open cold springtime temperature of 21°C/70°C fruit frame. Water them well and as plants grow will be produced much earlier. In the cool pot them on into their final 6 in pots using house melon seed can be planted in February 1 Mid-December Bring rooted plants in 6 in 2 Two weeks later raise the temperature to John Innes No. 2 or an equivalent peat-based and March to give earlier fruit in June and pots into the cool house. Make sure they 7°C/45°F. When flower trusses appear raise mix. Until September, liquid feed the plants July respectively. Remember to damp down are well spaced. Keep the temperature just it to 10°C/50°F. Ventilate and damp down once a week and water frequently. the house well except during pollination and above freezing. Liquid feed twice a week. when the temperature exceeds 21°C/70°F. Leave the plants undisturbed until Novem­ when the fruits start to ripen. ber then bury the pots up to their rims in peat or well-drained soil to prevent frost from Okra reaching their roots. Ideally, this should be Also known as gumbo and ladies' fingers, done in a cold frame but a sheltered corner okra are unusual vegetable fruits particu­ of the garden (not a frost pocket) will suffice larly good for cooking in curries and other if necessary. If there is any risk of frost damage, oriental dishes. They are not hard to grow close the frame or cover the plants with straw. but being tropical plants they need fairly Greenhouse cultivation In mid-December high temperatures, particularly for germina­ take the pots into the greenhouse and place tion and plant raising. them well apart on a sunny shelf to allow good Raising from seed Sow seed thinly in a seed air circulation and maximum light. For a fort­ flat filled with moist soil mix or sow them night keep the temperature just above freez­ singly in peat pots from February onwards. ing then raise it to 7°C/45°F. Do not be Cover the seeds with a thin layer of mix, tempted to turn the heating up any higher as water them in, then cover the pots or flats this will create too much foliage at the with a sheet of glass and one of newspaper. expense of fruiting capacity. When the flower Turn the glass once a day and maintain a trusses appear in February, raise the minimum temperature of 18°-21oC/65o-70°F. The seeds temperature to 10°C/50°F and ventilate the will take from one to three weeks to ger­ house a little during the daytime if the green­ minate, depending on the temperature. As house air temperature exceeds 21°C/70°F. soon as they are big enough to handle, prick At this stage plants will benefit if the house out the seedlings into 3 in peat or plastic pots is damped down once a week and if they are filled with John Innes No. 1 potting compost. 3 When the flowers open stop damping 4 When fruit has set resume damping given a high potash liquid feed twice a week. Greenhouse cultivation In early spring, plant down and increase the temperature to down. Support fruit trusses with forked When the flowers are open, increase the out okra direct into the greenhouse border 13°C/55°F. Ventilate the house at 24°C/75°F. twigs inserted in the pots. Stop feeding minimum temperature to 13°C/55°F but do soil or transplant them into 10 in pots of Pollinate the flowers daily with a brush. when fruit begins to color. Fruits and vegetables 2

John Innes No. 2 compost. Whichever method placed with a preparation made from sods is chosen, plants should be provided with of fibrous chalky loam stacked for six months canes for support and placed 21-24 in apart then mixed with one part of rubble to every in each direction. Throughout the growing ten parts of loam. A fortnight before planting season, water plants well and when they are in spring, mix in 8oz of John Innes base 9-12 in high, pinch out the growing points to fertilizer to every 2 gal bucketful of soil. encourage a bushy habit and a good suc­ Care of plants A peach will need a minimum cession of flowers and fruit. Watch out for temperature of 7°C/45°F from late winter signs of whitefly and red spider mite. until fruit is formed. Only ventilate the house Okra should be harvested when they are when the temperature rises above 18°C/65°F. young and the seeds inside their pods still Until the flowers open, damp down the house soft. Harvest between June and September. on sunny days and spray the foliage with clean water daily. In early summer, mulch Peaches plants well with rotted manure or garden In a large greenhouse, especially a lean-to, compost and apply a liquid tomato feed it is possible to grow a fan-trained peach or every 10 days from bud burst to the start of nectarine. Both these fruits will crop more fruit ripening. reliably in the cool house than in the garden. When the flowers open hand pollinate The best sort of peach to choose for a cool them with a small paint brush and when house is the common plum rootstock St fruitlets form thin them to about two per Julien A which is semi-dwarfing and so more cluster when they are about 1/2 in long. Thin manageable. again at the 1 in stage to leave fruits evenly Soil The border soil of the greenhouse can be spaced 8-10 in apart. 1 March Transplant young plants raised in 2 Pinch out the growing points to used but should be enriched with plenty of Care after harvesting After the fruits have heat direct into greenhouse soil or transfer encourage bushy growth and a good organic matter before a peach is planted. been picked, open the ventilators and leave them to 10 in pots. Space plants 21-24 in succession of fruits when plants are 9-12 in Alternatively, the border soil may be re­ them open until spring. apart and provide canes for support. tall. Guard against pests.

FAN-TRAINED PEACH

If space allows a fan-trained peach may be organic matter and provide wires 6 in grown against the back wall of a lean-to . apart for support. For early fruiting main­ greenhouse or under the roof of a double tain a minimum temperature of 7°C/45°F or single-span cool house. Ideally an area from late winter until fruits are formed and 3 Through the growing period water plants 4 June onwards Cut young pods as soon as of 15 ft x 10 ft is needed. Plant the tree ventilate only when the temperature regularly. If necessary spray against red they are ready, using sharp scissors, to give direct into greenhouse soil enriched with exceeds 18°C/65°F. spider mite using malathion or a similar a long cropping period. Remember that old low-persistence pesticide. pods are stringy and unpalatable. The year in a warm greenhouse 1

In theory, raising the greenhouse temperature considered to be raising food crops such as cool regime. Ventilators will not need open­ Electric fan heaters are also useful back ups to bring it into the warm category—minimum tomato, melon and lettuce, with a few sub­ ing until the temperature reaches 21-24"C/ for solid fuel systems. Fan heaters also have night temperature 13°C/55°F—greatly in­ tropical foliage plants to add interest, a cool 70-75°F. If, on days of cool winds, hot sun the beneficial effect of circulating air, Pests creases the range of plants that can be house will suffice, with the foliage plants and passing cloud banks the temperature and diseases, especially fungal diseases ,and grown. However, two important factors must kept in a large propagating case heated to briefly rises to 38°C/100°F, there need be no mildew, can be a problem all the year round be set against this benefit. First, the cost of warm greenhouse levels. Similarly if a large cause for alarm. Shading, however, is vital in a warm greenhouse. A buoyant atmo­ heating a greenhouse to warm level is very number of seeds are to be raised in the early especially as many of the plants grown come sphere, such as that produced by a fan high. Second, the range of plants easily spring, a propagating case of soil-heated from forest or jungle environments where heater, helps to prevent such troubles. available to gardeners and suitable for warm bench bed will be more economical. shade is dense and light intensity low. greenhouse conditions is relatively small. A medium sized greenhouse can also be Foliage plants The character of a well-stocked warm fitted with a partition and used as a combined Heating Many of the foliage plants cultivated in warm greenhouse is quite different from that of cool and warm house. The inner section can The heating system will need careful design greenhouses are widely grown as house cold and warm houses. Many of the plants then be double-glazed and fitted with a high- to ensure that it is capable of maintaining the plants. Some houses plants require a higher are grown for their foliage, which is often powered heating system, while the outer minimum temperature necessary. See pages minimum temperature than even a warm large and handsomely patterned. A warm part of the house is run as a cool house. This 20-21. Whichever fuel is chosen for the main greenhouse provides, but most will thrive in greenhouse full of foliage plants, ferns and allows plants to be moved from one to heating system, failures can occur. Electricity the better light and more even environment orchids has a lush, tropical feeling. The another when they are needed for flowering is subject to power cuts, which can affect of a greenhouse. The many books on house gardener's response to this markedly different or forcing. Bulbs can be placed in the cool gas and oil systems as well as electric ones plants describe the growing conditions atmosphere is a matter of taste, but the section after flowering, and plants raised by cutting power to pumps and igniters. needed. Bear in mind that while winter contrast between a warm house, which from seed in the warm house can be moved Solid fuel and oil systems may be forced out conditions in a warm greenhouse may be reproduces a different climate, and the cool into the cool section as the first stage in of action by fuel supply problems. A back-up ideal for some house plants, they may find house, which moderates an existing one, hardening off. system which uses another fuel is vital, for if summer temperatures there too hot. Shading must be appreciated. The routine management of a warm the winter night temperature is allowed to must be considered an essential when Before deciding on a warm greenhouse, greenhouse follows much the same pattern fall many valuable plants may be lost. A growing foliage plants. Among foliage plants the gardener should consider the plants to be as any other heated house. In general, kerosene heater, kept well maintained and suitable for warm greenhouse conditions are: grown. If the main use for a greenhouse is ventilation problems are fewer than under a with a full fuel tank, is a good insurance. Aphelandra squarrosa (zebra plant). Deep

January February March April May June Restrict watering to those plants Water more freely and ventilate in Ventilate freely on warm days and Ventilate for most of the day, but Increase watering, damping down Turn off and overhaul the heating in flower or active growth. sunny weather. maintain a more humid beware of night frosts, which can and shading as temperatures rise. system. Use a fan or kerosene Keep humidity low and ventilate Keep up cold weather precautions atmosphere. Shade susceptible still be sharp. Water freely, Continue feeding and pest and heater if unseasonal weather only around noon, maintain a such as insulation and draft plants from bright sun. Increase increase humidity by damping disease control. occurs. Ventilate freely and shade buoyant atmosphere. proofing. humidity by syringing, spraying and down and syringing, and shade Continue to sow primula and sow the house. Water twice a day if Sow begonia, gloxiana, Sow half-hardy annuals and begin damping down, keeping plants in when necessary. Where most cineraria for winter flowering. Sow necessary. Maintain humidity by strepocarpus in heat, also those sowing bedding plants. Sow celery flower dry. Begin feeding plants in plants require shade permanent Begonia semperflorens for winter damping down, spraying and seeds listed under Cold and Cool and brassicas for transplanting into active growth and those due for summer shading can be applied flowering. syringing frequently. greenhouses for sowing in a the open garden. Sow tuberous spring flowering. this month. Continue feeding and Take cuttings of most plants, Continue to sow primula, propagator. begonia seeds in a propagating Sow tomato, cucumber, pepper, be on the alert for increasing pest especially euphorbia, azalea, calceolaria, cineraria, and zinnia Bring in bulbs for forcing. Force case. eggplant, melon stocks, aster, and disease problems. Fumigate heaths, and begonia. Pot on for early autumn flowering in pots. early-flowering azaleas and other Take cuttings of chrysanthemum, zinnia, coleus. Prick off seedlings the greenhouse against pests if rooted cuttings and prick on Sow gloxiana and begonia for flowering shrubs. Force seakale, fuchsia, salvia and perpetual - grown from previous month's possible. seedlings. Harden off seedlings as flowering the following year. witloof chicory and rhubarb boxed carnations. sowing. Take softwood cuttings of necessary in a frame. Take cuttings of fuchsia, hydrangea, up in the autumn. Box up dahlia tubers in peat to Take cuttings of dahlia, fuchsia, camellia, fuchsia, osmanthus and Move remaining potted bulbs into tuberous begonia, rockea and other Take softwood cuttings of begonia promote growth for cuttings next hydrangea, solanum, salvia. other suitable plants. the open garden or frame for succulents. and geranium. month. Continue re-potting. Divide ferns Repot azaleas, camellias and other plunging. Pot chrysanthemums into flowering Root succulents, coleus, Continue re-potting and pot up and cannas if necessary. shrubs after they have finished Pot on gloxiana, celosia, begonia. pots. Pot on as necessary young philodendron, tradescantia and rooted cuttings. Stop decorative chrysanthemums flowering. Trim plants into shape Pot on chrysanthemums and stand plants grown from seeds and other plants which develop aerial Bring more bulbs and shrubs in for and perpetual carnations at the same time. Pot on fuchsia, the pots outdoors in full sun. cuttings. roots. flowering. propagated from cuttings taken petunia and zonal pelargonium. Hand-pollinate melons. Check perennials and re-pot those Bring in batches of primula, and earlier in the year. Re-pot orchids. Feed tuberous begonias. that are getting pot-bound. cineraria. Move orchids and camellias into Move seedlings of half-hardy Clear out unwanted, sickly or Force lily of the valley. shady areas of the greenhouse. annuals and bedding plants to a overcrowded plants. Bring in begonia tubers, place in frame to harden off before planting Prepare pots, flats and benches flats of peat and start into growth. out. Move winter-flowering bulbs for seed sowing and propagation. Pot up as leaves appear. to a frame and plunge. The year in a warm greenhouse 2

green, broadly white-veined leaves with as foliage plants, both having dark green succeeding pages. Annuals and the other light shade and moderate humidity. For spikes of yellow bracts and flowers. 2-3ft. leaves felted with purple hairs. C. aurantiaca flowering plants listed in the cool greenhouse propagation, see pages 60-61. ( alathea spp. Many plants in this genus are is shrubby, C. sarmentosa has a trailing habit. section can be grown in a warm house. Streptocarpus (cape primrose). S. rex/7 and its grown as house plants. They need a minimum Iresine spp. Several members of this genus Coleus Thyrsoideus. This sub-shrub carries hybrids have dark wrinkled leaves and clusters temperature of 16"C/60"F. C. Makoyana (pea­ are grown as short-term foliage plants in pots. clusters of blue flowers in winter. It is best of funnel-shaped flowers in a variety of cock plant) is one of the most striking, with The beefsteak plant (/. herbstil) has deep red- raised annually from cuttings in spring. 3 ft. colors. Shade tolerant. oval leaves yellow-green above with a bold purple oval leaves on red stems. Columnea. These trailing plants are very well patterning of large and small dark green ovals. Maranta leuconeura (prayer plant). This low- suited to hanging baskets. C. glorosa has Shrubs and climbers The same pattern is reproduced in red on the growing spreading plant can be used at the pendant chains of small reddish leaves and The following species which survive at a undersides of the leaves. 3 ft. front of a bench bed. Species have varied- tubular red flowers in winter and spring. winter minimum of 13°C/55°F. Cyperus altemifolius (umbrella grass). Not colored leaves. Crossandra infundiluliformis. A shrubby peren­ Acalphya hispada. This shrub has large oval botanically a grass, this plant provides a Peperomia spp. Plants from this genus grown nial, this plant carries fan-shaped pink to red leaves and crimson tassel like flower clusters. valuable contrast to broad-leaved plants. It for their foliage have shrubby, trailing and flowers for much of the year. The foliage is It will grow to 6 ft, but can be kept to half this requires plenty of moisture. 2-4ft. climbing habits. Many are epithytes, and all attractive. 2-3 ft. height by pruning. Dieffenbachia (dumb cane). Species include need a free-draining soil mix. lusticia spp. Several are grown as annuals Antigonon leptopus (coral vine). Fast-growing D. amoena, with white spotted leaves and Pilea. Two species are grown as foliage plants. from spring cuttings. /. carnea has pink to and needing plenty of space, this twining D. picta with smaller, deep green ivory P. cadierei is a bushy plant with elliptic leaves purple tongue-like flowers in autumn. It can climber has narrow leaves and small bright flushed leaves. The variety D. p. 'Rudolph patterned with silvery blotches. P. microphylla reach 4-6 ft if regularly potted on. J.. rizzenii pink flowers in clusters. 10 ft or more. Roehrs' has longer, almost entirely yellow has sprays of small leaves. The inconspicuous has an arching habit and clusters of scarlet Coffea arabica 'Nana' (dwarf coffee). The leaves with whitish blotches and green flowers shed pollen explosively, hence the and yellow flowers for much of the year. coffee tree has shiny dark green leaves, mid-rib and leaf margins. All thrive best at vernacular name of artillery plant. Rhoeo spathaca (boat lily). Small white flowers fragrant white flowers and red berry-like above 16°C/60°F. 3 ft or more. are carried on boat-shaped bracts in the leaf fruits. 3-6 ft. Fittonia verschaffelti. This trailing plant has Flowering plants axils. Becomes clump-forming with age. 1ft. Dipladenia spendens. A vigorous twining olive-green leaves with an elaborate net­ Plants listed below are perennials. Other Saintpaulia ionantha (African violet). Easy to climber with large pink flowers. Tuberous- work of red veins. flowering plants appear in the bulbs list, and propagate, and compact, this plant has rooted, it should be cut back hard each Gynura (velvet plant). Two species are grown orchids and begonias are discussed on the become very popular. Maintain 16°C/60°F, winter. 10 ft.

July August September October November December Ventilate night and day according Prepare heating system for autumn Remove permanent shading and Reduce watering and cut humidity. Cut ventilation to the minimum, Maintain minimum temperatures, to temperature. Maintain a moist operation. Order fuel if necessary. start the main heating system, Continue to ventilate and provide opening the house only in the ventilate carefully and water atmosphere and keep all plants Use a fan or kerosene heater to setting the thermostat to maintain heat as necessary. Do not allow air middle of the day. Water sparingly sparingly. Only those plants in well watered. Shade as necessary. maintain night temperature in the necessary minimum night to become stagnant through and reduce humidity. Keep bloom or about to bloom will need If necessary, repaint the greenhouse unseasonal weather. Continue temperature. Continue to water inadequate ventilation, or mildew temperature above the minimum much water. Cure drafts and interior, choosing a spell of settled watering, shading and pest and and damp down freely and may occur. Wash down the glass, but not too warm. insulate wherever possible. weather for the task and moving disease control. ventilate when necessary. inside and out, to permit Re-pot lilies. Bring in early bulbs Bring in more bulbs for forcing. Cut the plants outside or into a frame. Sow more annuals for spring Temperatures may range from maximum light penetration during from the frame. back chrysanthemums as they Maintain the pest control flowering. Sow cyclamen. very warm to freezing, so control winter. Bring primulas and calceolaria in finish flowering, and place the program. Look out for and combat Take cuttings of half-hardy ventilation carefully. Pot up tulips and further batches from the frame or cool house for stools in a frame. Bring in azaleas, fungal diseases. bedding plants such as geranium, Pot up more bulbs for winter of other bulbs for winter and early flowering. deutzia, primula, cineraria and Continue to sow primula, also take softwood cuttings such flowering. Place cyclamen, spring flowering. Bring in remaining Lift and store begonia tubers. cyclamen for winter flowering. cineraria, calceolaria, also first as coleus, begonia, tradescantia, cineraria and primula into chrysanthemums. Box up seakale, witloof chicory and Force seakale and witloof chicory. batches of annuals for winter and regal and fancy pelargoniums. flowering pots. Re-pot all plants that have outgrown rhubarb for forcing. spring flowering. Feed and water chrysanthemums Bring into the greenhouse azaleas, their pots during the summer. Take cuttings of hydrangeas and placed outdoors. Tie them in to camellias and other perennials Bring in any perennial bedding other plants not propagated in stakes to prevent wind damage. which have spent the summer in plants and tub or pot fruit trees June. Pot up first batch of bulbs for the open garden. Bring in and shrubs needing winter Re-pot freesias and pot on cuttings winter flowering. Pot on cineraria chrysanthemums for autumn protection. and seedlings planted earlier in the and primula grown from seed. flowering. Plant climbers and fruit trees and year as necessary. Pot on perpetual Spray and wipe down the leaves of bushes. Feed cyclamen, camellia, carnations and place them in an foliage plants. cineraria and primula. open frame. Prune woody climbers. Pinch out Move remaining winter-flowering the flower buds on fibrous begonias shrubs to a frame or outdoor to encourage winter flowering. plunge bed. Using frames 1

A frame is a versatile piece of equipment placed round the walls. Whichever heating Growing early carrots in a heated frame which can be used as an extension <>l the system is chosen (see also pages 18-23) it greenhouse or on its own. A frame is parti­ should always include an accurate thermo­ cularly useful for a gardener without a green­ stat to aid careful regulation of the growing house, especially if it can be heated, for given conditions within the frame. the restrictions in size, a heated frame can be Insulation To help conserve the heat built up used for most of the plants that can be grown in a frame during the day, the frame lights can in a greenhouse. Both heated and unheated be covered on cold nights with burlap sack­ frames can be used for raising new plants, ing or a roll of old carpet. Place blocks of including early vegetables; for extending the wood carefully on top of the sacking or carpet growing season; for hardening off green­ to prevent it from blowing away. Alter­ house-grown plants before they are planted natively, buy a special sheet with eyelet out in the garden; for overwintering plants holes and tie it to wooden pegs placed in the such as chrysanthemums and for plunging soil. The sides of the frame can also be potted bulbs that will later be taken indoors insulated by lining them with bales of straw 1 February Dig garden soil in the frame. 2 Rake in 2-3 oz of general fertilizer then to bloom. The soil, mix or other growing encased in chicken wire. Place heating cables in the frame and cover water well. Close the frame. medium placed in the frame will depend on them with 6 in of good garden soil. the exact use to which the frame is put. Ventilation The main shapes and sizes of frames are Plants grown in heated and cold frames need described in detail on page 7. The frame good ventilation to encourage free air circu­ should be deep enough to accommodate the lation. Poor ventilation increases air humidity plants to be grown in it. within the frame and encourages the growth of disease-causing organisms. Make sure that Siting the lights of the frame can be opened at A frame can be placed abutting a greenhouse several different levels and that they can or on its own. If one wall of the frame is easily be removed altogether. For ventilation placed against the greenhouse wall the frame the lights may be propped open with a block will benefit from improved insulation and re­ of wood, or a brick, or pushed back entirely duced heat loss. Another advantage is that off the frame and placed at an angle over the the heating system of the greenhouse can frame with one end on the ground, as long usually be extended to serve the frame. Place as they will not blow away. In very windy a frame that is to be used on its own in an weather secure the lights with cord wound 3 A week later Sow seed in drills 4 in apart 4 March As seedlings develop thin (if open, sunny, easily accessible position that round cleats screwed to the frame wall, or or broadcast at 1/12 oz per square yard. Set necessary) to 1—11/2 in apart. Remove all affords plenty of light and some shelter from by hooks and eyes. thermostat to 18°C/65°F. Keep frame shut. thinnings. Water to firm. Replace lights. high winds. Never place a frame in a corner of the garden known to be a frost pocket. The Watering general rules for siting frames and green­ To water the plants in a frame the lights can houses are further explained on pages 12-13. simply be lifted or removed. Always water plants with a rose fitted to the watering can Heating or hose so that soil is not washed away from A cold frame, that is a frame with no form of around plant roots. Semi-automatic watering heating, is less useful than a heated frame with a perforated hose or capillary watering which will allow a wider range of plants to be as used in the greenhouse (see pages 24-26) grown. In a heated frame, early vegetables are also effective and time-saving. In the will be ready for cropping sooner and there capillary system, water is supplied via a trickle is less chance of tender plants failing to sur­ irrigation line which ensures a slow, steady vive the winter. A heating system for a frame water supply to the growing medium in the works by heating the soil and/or the air. Soil frame. When the frame is not in use and in the heating can be provided by electric cables or, summer, remove the lights so that the soil can if the frame is abutting a heated greenhouse, get a good natural watering from the rain. 5 As weather warms open lights on sunny 6 April Remove lights completely when all by hot water pipes. The air in a frame can be This will also help to prevent a damaging days but close them at night. Plants will chance of frost is past. Store lights in a heated by electric cables or hot water tubes build-up of mineral salts in the soil. now need more water. safe place. Harvest carrots as needed. Using frames 2

Light and shading drainage or, if a capillary watering system is on a perforated polyethylene sheet placed in tains heat better and is cooled less by the To ensure maximum entry of light, keep frame used, on a 2 in layer of coarse sand placed on the frame. If necessary, make provision for wind. Vegetables sown in a cold frame will lights clean at all times and renovate and a thick sheet of polyethylene. Note that seeds any particular needs of the crop to be grown still crop earlier than those sown outdoors clean them in summer. As in the greenhouse, planted in pots or boxes will need more care —lettuces for example do best in humus-rich with no protection. Among the best crops for plants in a frame risk being scorched and in watering as they dry out more quickly than soil while carrots prefer soil that has not been the cold frame are cucumbers, zucchinis, badly damaged by hot sun. To prevent this, those planted direct into the soil. Seedlings of freshly manured. melons, smaller squashes and outdoor tom apply a shading compound to the inside of tender or half-hardy plants raised in a heated Care of seedlings Freshly sown seed of most atoes. Cucumber and similar seeds are best the frame lights as necessary, or place a sheet frame will also need hardening off before vegetable crops will germinate best at a tem­ pre-germinated at a temperature of 21°C of muslin or small mesh plastic netting over they are planted out into the garden. perature of 18°C/65°F so this is the ideal 70°F before being planted in the cold frame the frame on hot, sunny days. The covering thermostat setting for seed planted in late in early May. Ventilate the frame as necessary can be rolled back in cloudy weather. Early crops in a heated frame winter or early spring. On cold nights, insu­ during the day and close it down at night Carrots, radishes, lettuces, beets and spring late the frame with burlap or similar material. until plants are established then remove the Raising seed onions are among the many vegetables that The frame should be ventilated during the lights in June. Seed of all kinds can be sown in a heated or can be grown in a heated frame for early day as long as the weather is not very cold or For outdoor tomatoes, raise seeds indoors unheated frame in pots, boxes or flats or cropping and for eating when young and windy. In bad weather ensure maximum and plant them out in the cold frame in May directly into prepared soil. Turn on the heat­ tender. Months of planting for heated frames entry of light by washing all debris off the or early June. Ventilate the frame as neces­ ing system, if there is one, for a day or two are shown in the list above. lights regularly. As the weather warms the sary but do not remove the lights completely before sowing to warm the soil. Seeds of Soil Most early crops can be sown in the lights can be opened wider during the day until the plants are well established, by hardy plants can be sown in a heated frame frame direct into good well-dug garden soil and closed at night. Once all risk of frost is which time they will have probably outgrown as early as February, seeds of tender plants enriched with well-rotted manure, compost past and plants are well established, the the height of the frame. The lights can be from late February to March. For an un­ or peat, plus 2-3 oz of a general well-balanced lights can be removed altogether, cleaned replaced at the end of the season to help heated frame, add on another month to six fertilizer per square yard. If the garden top and stored and the heating system turned off. ripen the last fruits and combat frost. weeks in each case, and more if the spring soil is very stony or shallow, it may be prefer­ is a cold one. Seedlings in pots or boxes are able to replace the top 1-11/2 ft with new Crops in a cold frame Cuttings best placed in the frame on a 3 in layer of good-quality top soil or to replace the soil For vegetables, a cold frame provides similar Cuttings of all types can be grown in a frame. gravel or weathered ashes to allow good completely with good sterilized soil placed protection to cloches (see page 94) but re­ Use a heated frame for cuttings of tender

Hardening off in an unheated frame

1 Spring As air temperature rises, place 2 During first week (weather permitting) 3 During second week leave lights open a 4 In third week remove plants from the boxes or pots of greenhouse-reared leave lights half open during the day for little at night. Towards end of week remove frame and plant in their permanent seedlings or cuttings in the frame. ventilation but close down each night. lights completely except in windy weather. positions in the garden. Using frames 3

Overwintering and storage The plunge bed A frame can act as a useful protected storage A plunge bed is a bed of damp sand, peat or a OVERWINTERING site for plants during the winter and, at the mixture of gravel and weathered coal ashes Softwood shrub cuttings can be planted in a same time, save valuable space in the green­ 1ft deep into which pots are buried or cold frame in June, semi-hard ones in July house. A heated frame will be needed for plunged up to their rims. A plunge bed in a and August. See pages 57-59 for details. tender plants such as pelargoniums and cold frame is useful for accommodating fuchsias which should be placed in the frame plants throughout the year. From spring on­ Hardening off in September. In the same month, freesias wards, as alpines finish flowering in the alpine Many tender or half-hardy plants raised in the can be potted up and placed in a heated house, transfer them to the plunge bed. greenhouse need to be put through a "tough- frame. Outdoor chrysanthemums can be Plunge the pots up to their rims and keep the ening-up" process called hardening off before overwintered in an unheated frame after they bed damp but never let it become dry or they are planted out into the garden. A cold have been cut back and boxed in a pro­ waterlogged. The cool moist environment of frame is ideal for this purpose. In spring, when prietary potting mix. The frame should be well the plunge bed will produce good strong there is no risk of tender or half-hardy plants ventilated except in very severe weather to growth. Similarly, pot-grown greenhouse Heated and unheated frames are very use­ being exposed to frost once they are in their help prevent diseases such as botrytis, which plants can be plunged in summer, which will ful for storing and protecting flowering permanent positions in the garden, take pots are encouraged by stagnant air. prevent them from drying out too quickly. plants in winter, so freeing valuable green­ or boxes of young plants from the greenhouse Storage A cold frame can be employed to During the summer there is no need to place house space. Use a heated frame for and place them in the frame. For one week store dormant bulbs and tubers that are the lights on the frame. tender plants such as pelargoniums. Lift leave the lights open during the day (as long susceptible to frost damage. After lifting Bulb forcing In winter, use the plunge bed for plants from the garden in autumn, cut as the weather is not cold or windy) but close dahlia tubers, for example, pack them in forcing bulbs. Plant bulbs in pots, plunge them them back and plant in boxes before them at night. During the second week, leave boxes of dry peat before storing them in a and cover the pots with a 3 in layer of peat. placing them in the frame. Similarly, make the lights open a little at night. Towards the heated frame. Store bulbs in a cold frame Place the lights over the frame, leaving them chrysanthemum "stools" by cutting back end of the second week open the frame as loosely packed in wooden boxes with plenty open a little for ventilation. After eight weeks plants to within 4-6 in of the ground wide as possible at night. In the third week of room for air to circulate between them. the bulbs will have formed good root systems before boxing them up and placing them the plants can be planted in their permanent Make sure the frame is well ventilated but and can be taken indoors in succession for in an unheated frame. Ventilate well.. positions in the garden. guard against damp which can cause rot. flowering.

Plunging bulbs in an unhealed frame

1 October Fill frame with a 1 ft layer of sand, 2 Plant hyacinth bulbs in pots then plunge 3 Place lights over frame to protect pots 4 After eight weeks Remove pots from peat or a mixture of gravel and weathered up to their rims in the frame. Cover with from heavy winter rainfall. Keep the frame frame and take indoors in sequence for coal ashes. Water and allow to settle. a 3 in layer of peat to exclude light. well ventilated. flowering. Using cloches

Cloches provide plants with virtually the same over. Any cloches likely to be overturned by protected according to its specific needs and protection as cold frames, except that they strong winds should have fittings to anchor make sure that the same crop is not grown STORING CLOCHES retain heat rather less well and that the air them to the ground or should be secured in the same soil two years running. Before inside them is cooled more quickly by the with string tied to pegs placed in the ground. sowing seed or planting out seedlings raised wind. The advantage of cloches is that they Leave plenty of room between rows of in a greenhouse or heated frame, put the are more mobile and versatile to use. Cloches cloches for easy access and watering. cloches in position and leave them for two can be employed in many ways—to warm to three weeks to dry and warm the soil. A the soil before seeds are sown; for raising Ventilation dressing of balanced fertilizer can be raked in seedlings, especially half-hardy annual bed­ Ventilation is essential to prevent the build­ before cloches are positioned. ding plants and vegetables to extend the up of stagnant, over-moist airthat encourages growing season at each end of the year; to disease. If single cloches are placed in rows, Watering protect individual plants, particularly alpines, always leave a small gap between each one Cloches need only be removed for watering from cold and wet and to save blooms from if the cloches have no built-in ventilation if they are covering small seedlings which splashing and spoiling by mud; to provide system such as adjustable top or sides. In the need a very even sprinkling of water. Other­ shelter from cold and wind and to ripen off case of a polyethylene tunnel sides can be wise, water can be applied to cloches from onions and similar crops in poor weather. lifted and supported with a pot or wooden overhead with a watering can or hose if there Cloches can also be used to spread the season block. The gaps between the cloches can be is insufficient rain. The water runs down the of cut flowers. Rows of gladioli, for example, increased if necessary to let in more air, but sides of the cloches and is absorbed into the tend to flower at the same time, but if half is to avoid too much draft, and consequent soil, reaching the roots of the plants which cloched, the cutting period is lengthened. heat loss, close the ends with purchased grow naturally towards sources of food and cloche ends or with a sheet of glass or thick water. For long rows of cloches it is also Using cloches plastic held in place with a wooden stake. possible to supply water via a sprinkler or Store cloches not in use by stacking them Cloches should be placed in an open position irrigation tubing placed between the rows. on their ends in a sheltered corner of the away from the shade of trees. Never put them Soil preparation On light soil make a shallow channel on the garden where they will not get broken or in a very windy place where they will cool Before placing cloches in position, prepare outside of each cloche in which water can blown over by strong winds. quickly and risk being damaged or blown the soil for the plants or crop that is to be easily collect and drain into the soil.

Year-round uses for cloches

1 January Place cloches over soil prepared 2 Early spring Use cloches to protect newly 3 Autumn In rainy weather place harvested 4 Winter Single cloches can be put over for seed sowing. Leave for 2-3 weeks to dry sown seed and seedlings. Close cloche ends onions under cloches to dry out before alpines such as cushion plants susceptible and warm soil. Do not close cloche ends. but ventilate well according to type. storage. Ventilate well. Leave ends open. to rotting in wet soil.