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FLORICULTURAL PRODUCTION AND MANAGEMENT Part I: Background and Introduction

Neil Anderson

Horticulture is the fastest growing segment of The diverse number of produced requires each within the United States. An array of employee in the distribution channel, including floral products provides market diversity for the breeder and producer companies, distributors, industry. These include flowering potted propagators, pre-finish and finish growers, and , foliage plants, cut , cut foliage, annual retailers, to be trained in maximizing growth bedding and plants, and herbaceous biennials potential and quality. Knowledgeable and perennials. In 2003, the wholesale value of U.S. implementation of optimal post- care and floricultural crops was $5.07 billion for 11,913 handling treatments ensure maximum product shelf growers with sales greater than $10,000 and 929 life for the retailer and maximum performance for the million ft2 in production. For growers with sales consumer. Keeping up-to-date with the latest greater than $100,000, the crop total was $4.76 production techniques ensures sales of top-quality billion. While this crop category is in the top five plants which will maximize earning potential. "crops" surveyed by the U.S. Department of Agriculture, it contains multiple commodity groups Knowledgeable manipulation of the growing with hundreds of species. The largest environment is required to maximize floriculture floriculture commodity is bedding and garden plants production and profit, as well as to continue the at $2.42 billion (51%), followed by potted flowering tradition of grower excellence in the Midwest. Refer plants at $829 million (17.4%), potted foliage at $623 to the , Container Production, Pest million (13.1%), herbaceous perennials at $620 Management, Insect Management, Disease million (13.0%), at $425 million (8.9%), Management and Water Management in this manual propagative material at $351 million (7.4%), and cut for additional information. foliage or greens at $109 million (2.3%).

This industry enhances the lives of every citizen by providing color and interest to indoor and outdoor environments. power and convenience are two important features of floricultural crops, particularly annual bedding plants. In Minnesota, annual, perennial, groundcover, herb, , and potted production is valued at a wholesale value of nearly $86 million and it continues to grow! More than 250 Minnesota commercial companies produce these crops in approximately 13 million ft2 of space consisting of glass, fiberglass, rigid plastic, and film plastic , plus shade houses. In the near future, the industry estimates that the sales of annuals and perennials will increase by 30%. Part of this anticipated growth will arise from the many new crops entering the market each year, as well as the extended summer sales opportunity for bedding plants beyond the traditional Mother's Day to Memorial Day sales period.

43.1-1 1106

FLORICULTURAL PRODUCTION AND MANAGEMENT Part II: Greenhouse Production and Management

Terry Ferris

Flower Induction, Initiation and Development in between 35o F and 48o F. For example, perennials Floriculture Crops such as Asclepias tuberosa and Astilbe need twelve Growers always strive to have healthy, vigorous weeks of cold to break dormancy and flower. foliage on greenhouse crops, cut flowers and most Hydrangeas and require six weeks of cold to bedding plants. Growers also need to ensure the develop flowers. Tulips and initiate timely presence of flowers on flowering crops. flowers during the warm summer, however, they However, before a plant can flower, the plant must need a cold treatment to promote rooting, reach a physiological readiness, and then, either reach elongation and subsequent floral development. plant maturity or receive an environmental stimulus to induce the plant to flower. Once induced to Light Intensity and/or Accumulated Light – Light flower, flower parts are initiated at the tip of the intensity controls floral induction and initiation in . The initiated parts then develop by some species. African Violets need a minimum of enlarging and taking on qualitative changes such as 500 foot-candles for flowering. Zonal Geraniums color and fragrance. Floral induction and initiation will not flower when light intensity is too low. are controlled by one set of conditions while floral development may be controlled by the same or by Daylength – Plants measure the length of the light different set of conditions. Several different floral and dark periods of the day through phytochrome control mechanisms exist in the plant world. pigment which absorbs red and far-red light. This Growers need to know what controls flowering in phenomenon is referred to as Photoperiodism. order to schedule the production of a crop. Growers Darkness also affects phytochrome in a similar should consult supplier brochures, industry manner that far-red light does. It is actually the colleagues, or the scientific literature to identify length of the darkness that is most important in specific mechanisms. Floral control mechanisms or controlling the phytochrome response. The common plant conditions are described as follows: photoperiodic response groups include the following:

Age of Plant or Number of – In some plant 1. Obligate Long-day Plants species, the age of the plant, or more specifically, the Obligate Long-day plants flower only when the number of leaves formed, controls when the length of the day is greater than some critical induction and initiation of flowering will occur. For minimum time, which is usually 12 hours. example, Cyclamen start initiating flowers after Examples include Wave Petunias, Lobelia and seven or eight leaves are formed. Easter Lilies start Gazania. Many of these plants bloom naturally in flowering after 86 to 93 leaves have formed and Corn the summer. will flower after 22 leaves have formed. 2. Obligate Short-day Plants Specific Temperatures – For many plants, a specific Obligate Short-day plants flower only when the temperature range is required for floral induction and length of day is shorter than some critical initiation. For example, Cineraria initiates after maximum which is usually 12 hours. Many of four weeks at 45-55o F and Calceolarias need six these bloom naturally in the fall and include weeks at 50o F to flower. , and Kalanchoe.

Vernalization – Some floricultural crops require an 3. Day-neutral Plants exposure to cool temperatures for extended periods of Day-neutral plants are plants whose floral time to either initiate flower buds or to promote floral induction and initiation are not controlled by day development. In , this temperature is generally length. Examples include Roses, , between 32o F and 50o F. Growers use a temperature Nicotiana and Centrathus.

43.2-1 0510 4. Facultative Long-day Plants exchange, the side walls may be constructed of Facultative Long-day plants flower faster or have inflatable poly tubes with an inflation fan connected more flowers under long-days. Flowering is not to a thermostat that will inflate the tubes, or deflate specifically controlled by photoperiod, but is and collapse the tubes to let in fresh outside air influenced by it. Examples include Petunias, depending upon the temperature. Pansy, Dianthus and Sunflowers. Purlins – Purlins run horizontally from rafter to rafter 5. Facultative Short-day Plants and provide additional support. These may be Facultative Short-day plants flower faster or have especially important in high wind and heavy snow more flowers under short-days. Flowering is not load areas. specifically controlled by photoperiod, but is influenced by it. Examples include Zinnia, Ridge – The Ridge refers to the peak of the Cosmos and Rieger Begonias. greenhouse where the two sides of the roof meet. Round roofs would not have a distinct Ridge. Growers need to be aware of conditions that control floral induction and initiation as well as those that Eave – The Eave of a greenhouse is where the influence floral development. The two processes sidewall meets the roof. When the Eave of one may require different conditions. greenhouse is common with an adjacent greenhouse, the Eave area is referred to as the Gutter. Greenhouse Structures Greenhouses are built with a slight drop from one end The short growing season in the upper mid-west wall to the opposite end wall to allow gravity to limits year-round outdoor production of many facilitate the runoff of water down the Gutters. This floriculture crops. Therefore, greenhouse production water can be collected in underground storage tanks is an essential part of many commercial floricultural and used for irrigation or on the cooling pads. operations. The greenhouse structure that a grower selects will be influenced by the initial capital Span – The Span of a greenhouse is the width, or available and the cultural requirements of the crops to distance from one Eave to the next Eave, both being be grown. Structural components of greenhouses are under one Ridge. described below and pictured in Figure l.

Rafters – Rafters provide vertical support and can be part of a triangular truss or they can be arched as in quonset-type greenhouses. Spacing of the rafters influences the strength of the structure. Rafters are generally spaced on two- to four-foot centers. Very wide greenhouses require reinforced rafter and truss construction.

End Walls – End Walls on the north side of a greenhouse may be of solid, non-transparent construction for added strength and energy conservation.

Side Posts and Columns – Side posts and columns establish the height of the greenhouse and provide Figure 1. Basic structure components of a vertical support. Older greenhouses had eight- to greenhouse: A. Ridge, B. Rafter, C. End nine-foot sidewalls, while newer greenhouses are Wall, D. Side Post, E. Side Wall, F. frequently 10 to 12 feet or more tall. Taller Purlin, G. Eave/Gutter. greenhouses allow for a layer of hanging baskets that are high enough above the crop below to avoid Some structural modifications exist to enhance excessive shading of that crop. greenhouse ventilation. Ventilation is the exchanging of inside air with outside air and is essential to Side Walls – Side walls may be constructed with control temperature and humidity within the vents at the eave. To provide additional air greenhouse. Historically, ridge vents and side vents

43.2-2 0510 have been used for this purpose. Growers have 2. Free-standing Gable Greenhouse increasingly been adopting the use of inflatable Free-standing Gable greenhouses are framed sidewalls and roof designs that completely open the using steel, aluminum or . Steel provides roof in order to allow for better ventilation and air the strongest support and wood the weakest exchange. support. Any wood used should be treated to prevent decay under the expected humid There are many greenhouse designs, and there are conditions. Copper napthanate and other wood advantages and disadvantages of each. Lean-to preservative products approved for use around greenhouses are seldom used commercially due to plants can be obtained through a greenhouse difficulty in integrating automation. They also have supply company. Gabled greenhouses can be limited space and they have problems with proper covered with almost any type of covering as environmental control. The three most common described below. A series of free-standing types of commercial greenhouses are described greenhouses allows a grower to run different below: environmental conditions in each house and, therefore, grow a wide variety of crops that 1. Single Quonset or Hoop House require different growing conditions. Separate Quonset or hoop houses are frequently houses also allow for isolation of crops for insect constructed of aluminum framing and are one of and disease management. Connecting the the most economical and long lasting greenhouse greenhouses to a common work area or structures (Figure 2). However, they have limited Headhouse can facilitate their use in cold vertical headroom, especially along the side walls, climates (Figure 3). which can limit growing space, and reduce space utilization efficiency. When covered with a double layer of poly, they have good energy efficiency, in part due to the lack of seams in the poly covering. This creates a tight greenhouse that traps humidity, which condenses on the inside of the roof. Condensation dripping from the roof onto plants below can cause favorable condition for the development of diseases. To prevent this dripping, anti-condensation products can be sprayed to the inside of the covering. Or the roof . design can be changed to create more of a peak

that is not as flat as the top of an arch, which will Figure 3. Free-standing Gable Greenhouse. cause condensation droplets to roll down the side

walls.

3. Gutter Connected or Ridge and Furrow Gutter connected or ridge and furrow greenhouses are two or more Gable greenhouses placed side by side (Figure 4). This arrangement can provide very efficient growing spaces as automation of equipment is easily accommodated in the large open spaces inside. There are a limited number of side walls exposed to the outside which reduces total energy loss. Temporary inside walls can be created by attaching poly to the inside of the gutter and dropping it to the floor. This accommodates growing crops with different cultural requirements.

Figure 2. Quonset or Hoop House. W. Width, L. Length, H. Height.

43.2-3 0510 in polyethylene production uses the co-extrusion process. Three liquid resins are extruded simultaneously creating a single layer of film with three different chemistries across it. In the present tri-extruded films, the inner core may contain an anti- fog surfactant, a UV-inhibitor or an infra-red (IR) blocking chemical. These additions are designed to add extra properties to the film. The anti-fog should Figure 4. Gutter Connected or Ridge and Furrow reduce condensation build-up on the interior of the Greenhouses. film. UV-inhibitors slow down the rate of UV break- down of the film, while the IR blocking agents help to keep heat in the greenhouse by trapping in infrared Greenhouse Coverings or Glazings radiation. Glazings or covering materials for greenhouses vary in light transmission, heat retention, longevity and Fiberglass-reinforced Plastic (FRP) – Fiberglass- cost. A grower needs to consider cultural reinforced Plastic is not as popular today as it once requirements of a crop when selecting a glazing was due to its susceptibility to breakdown by UV material to use. High light requiring crops like Roses light, resulting in a ten-year maximum life span. The and Geraniums may perform better under a glazing stronger corrugated sheets are used on the roof and that lets in high light levels. Bedding plants tolerate a the weaker flat sheets are used on the side walls. wider range of light intensities. A greenhouse with Light transmission is about equal to that of glass, but numerous structural support pieces will also have the light is more diffused resulting in less shadows. lower light levels due shading, compared to a Heat retention is only slightly better than glass. The greenhouse with fewer support structures. bi-wall products discussed below have become good Commonly used greenhouse coverings are described replacements for fiberglass products. below. Double Layer Rigid Acrylic Panels – Double Layer Glass – Glass transmits high levels of light, but the Rigid Acrylic Panels are known for their high light number of sash bars needed to support the panes transmission, long life of over 30 years, and 60% cause shadows, thereby reducing the overall light energy savings compared to glass. It is flammable transmission. Heat loss is also relatively high due to which does deter some growers from installing it. the high conductance of heat through the glass, as Anti-condensate coatings are available for this well as the seepage of heat around the sash bars. product. Glass houses are expensive compared to alternatives, but they do have the advantage that they can last for Double Layer Rigid Polycarbonate Panels – Double over 30 years. Layer Rigid Polycarbonate Panels have the same 60% energy savings as the Acrylic Panels. However, Polyethylene Film – Polyethylene film is almost the Polycarbonate product has been more popular for always used as two layers with 0.5 to 4.0 inches of air commercial greenhouses due to its lower price, flame space between the layers to serve as an insulating resistance, and greater resistance to hail damage. dead air space. A small squirrel-cage fan is mounted Polycarbonate does turn yellow due to UV inside the greenhouse to inflate the space between the breakdown, therefore, it has a shorter life expectancy two plastic layers. The outer layer should be the of approximately ten years. Polycarbonate is stronger layer of six mil polyethylene, while the inner available in flat and corrugated single layer sheets layer only needs to be four-mil polyethylene. although energy conscious growers have preferred the double layer panels. Ultra-violet (UV) light can break down the polyethylene causing it to yellow and turn cloudy, Temperature Control In the Greenhouse which reduces its light transmission. Therefore, all Environment polyethylene used for covering year-around Growers must constantly evaluate the internal production greenhouses, has a UV inhibitor environmental conditions within the greenhouse in incorporated into it. Without this inhibitor, the order to achieve a desired rate and type of plant polyethylene film would last for only one heating growth. When any one of the five environmental season, rather than four years. The latest technology factors for plant growth is limiting, growth will be

43.2-4 0510 compromised. Growers must monitor and adjust the temperatures to be below 70o F. Temperature can environment to optimize all aspects of the also influence the rate of floral development or even environment for each crop including temperature, the number of flowers present in crop species that light, water, gases and nutrition. have alternative floral induction and initiation control mechanisms, other than temperature. Temperatures Uniform light, temperature and humidity across the above 80o F or below 54o F frequently decrease the greenhouse will promote uniform growth and number or flowers initiated in crops. Snapdragons, development of the crops being grown. Under Zonal Geraniums and Fuchsias all become less normal conditions, warm air will rise and it is floriferous as the temperature increases above 80oF. common for the temperature at floor lever to be 10 to It is important, therefore, for growers to know what 15o F cooler than the temperature at the eave. This controls floral induction and initiation in each crop stratification of temperature is an important and use that information concurrently with consideration when monitoring and controlling the determining temperatures for unfolding rates. temperature. Temperature sensors should be placed at plant level as that is the level where the Effect of Temperature on Growth – The temperature will influence the growth of the plants. temperature of the root zone of a plant will greatly influence the growth rate of the crop. Growing plants Day and Night Temperatures – Plants are adapted to with a warmer root zone temperature than air optimize growth under the natural outdoor temperature can maximize plant growth while environment of warmer days and cooler nights. conserving energy for greenhouse heating. The root Warm days maximize photo synthesis while cooler zone can be warmed by sun exposure directly to the nights minimize respiration. The result is a , or by root zone heating. Locating heating pipes maximization of dry matter accumulation and the or hot water heating tubes under the greenhouse growth of the plant. Growers mimic this temperature benches or installing hot water hearing tubes under by using an average of five to ten degrees F warmer the greenhouse benches, or installing hot water day temperature than night temperatures in the heating tubes in the greenhouse floor are common greenhouse. methods to deliver heat more directly to the root zone. Average Daily Temperature – The average daily temperature is calculated by adding the day Controlling Plant Height with Temperature – The temperature to the night temperature and dividing by height of a plant is determined by the number of two. Typically, the higher the average daily nodes present and the length of the internodes. The temperature the faster the growth rate of plants. elongation and length of the internodes is controlled by the difference (DIF) between the day and night Optimizing Temperatures for Specific Crops – The temperature. DIF is calculated as follows: rate at which a plant develops or grows can be quantified by calculating the rate of leaf unfolding on DIF = Day Temperature – Night Temperature the plant. Each crop will have an optimal temperature for leaf unfolding, which is generally Positive DIF values result in long internodes. between 54o F and 86o F. Temperatures outside of Negative DIF values result in shorter internodes. this range will decrease the rate of development. For Maintaining one constant temperature throughout the example, grown at an average daily day and night, which equals a zero DIF will result in temperature of 68o F will unfold one new leaf per plants that will generally be 70% shorter than if the day. The leaf unfolding rate models for several plants were grown at a + 10 DIF (68o F Day – 58o F commercial floriculture crops are available in the Night). This response has been documented for a scientific literature. Growers can monitor the leaf wide variety of floriculture crops, including bedding unfolding rates for a specific crop and make plants. DIF and growth retardants limit cell comparisons from year to year to assist in accurate elongation and division by influencing the plant timing of the crop for target market dates. hormone Gibberellic Acid (GA) synthesis in plants.

Controlling Flowering with Temperature – Floral The temperatures during the first three to four hours induction and initiation is specifically controlled by after sunrise are responsible for determining about temperature for some floriculture crops. For 70% of the elongation that takes place due to warm example, Freesias and many Primulas require day temperatures. Therefore, by dropping the

43.2-5 0510 temperature five to ten degrees below the night Condensation on the leaf surface can also be reduced temperature for the first three to four hours of by lowering the humidity level. Opening ridge vents daylight, 70% of the negative DIF or shortening of to bring in cooler drier air, and allowing warmer the internodes will be achieved. The negative DIF humid air to rise up and out of the greenhouse, will effect can be used as a non-chemical means of lower the humidity level in the greenhouse. controlling plant height. The morning temperature Greenhouses with computerized environmental drop is easier and more practical to maintain than control systems can use “heat and vent” cycles called keeping the day temperatures cooler for the entire Purging to expel the humid air. Growers will heat day in the greenhouse. The three- to four-hour the air two to five degrees warmer than the desired morning temperature drop does not affect the overall set temperature and simultaneously open the ridge growth rate of the crop as would an entire day of vents for two to five minutes. The computerized cooling. The morning temperature drop is also more environmental control system can monitor energy efficient than maintaining a warmer night temperature and humidity levels and predict when temperature. condensation will occur, and then implement the purge automatically. Propagation facilities need to Negative DIF environments can result in some side maintain higher humidity levels. Mist systems or fog effects. Many plants will show downward curling or systems are installed to deposit very small water bending of the leaves or petioles. Seedlings may droplets into the air to achieve higher humidity show chlorosis. However, DIF is a daily response, levels. therefore, if the environment is changed to a positive DIF for a few days prior to shipping the crop, these Lighting in the Greenhouse side effects will usually be reversed. Light is an energy source for plants. Plants contain light absorbing chemicals called pigments. Different Light intensity and Daylength will affect how a plant pigments absorb different wavelengths or colors of will respond to DIF. The higher the light intensity, light. The pigment absorbs red and blue the more responsive the plant is to DIF. Plants are wavelengths of light which are involved in also more responsive during short days. This . It is critical that adequate light be explains why differences in the effectiveness of DIF available to all plants to ensure optimal are apparent at different times of the year. photosynthetic rates for leaf and flower development as well as dry matter accumulation. Please see Humidity in the Greenhouse Chapter 13, Plant Growth and Development for Warm air holds more moisture than cooler air. additional information. Therefore, as temperature stratifications occur in the greenhouse, humidity stratifications also occur. Insufficient Light – Lack of sufficient light can be a Temperature and humidity stratifications create non- limiting factor for plant growth in a greenhouse uniform growth within a crop, they are energy environment, especially in the winter. Plants inefficient, and these conditions can create disease growing under low light conditions may exhibit slow problems. Inside corners of the greenhouse are dead growth rates, chlorosis, small new leaves, stretching zones where temperature and humidity levels can of the internodes, delayed flowering, and aborted become undesirable, thereby creating ideal conditions flowers. While light intensities may reach as high as for diseases to develop. When the sun sets, the leaf 10,000 foot-candles (2,000 µmol/m2/sec) at noon surfaces become cooler as the sun is no longer during a clear day in June, light intensities as low as warming the leaf. But, the leaves continue to radiate 500 foot-candles (100 µmol/m2/sec) are common in heat into the cooler night air. Moisture in the warm greenhouses during cloudy days in December. Most humid air potentially condenses on the cooler leaf plants are light saturated for maximum surface, thereby creating a moist environment on the photosynthetic rates 2,000 to 3,000 foot-candles (400 leaf for fungal and bacterial development. Mixing to 600 µmol/m2/sec. When natural lighting is less the air within the greenhouse with Horizontal Air than 2,000 to 3,000 foot-candles, artificial lights that Flow (HAF) fans will help mix the air layers and have adequate red and blue light qualities can minimize temperature and humidity stratifications. enhance the photosynthetic productivity of plants. HAF is a common strategy to promote uniform Lamps that provide 300 to 600 foot-candles (40 to 80 growth and minimize disease potential. µmol/m2/sec), such as high pressure sodium vapor lamps of metal halide lamps, are used 16 to 24 hours per day.

43.2-6 0510 Excess Light – In the summer when light intensities cause delayed and/or inhibited floral initiation and far exceed 2,000 to 3,000 foot-candles, a large development in Poinsettias. portion of the light reaching the leaves is wasted. The excessive light can cause photo-oxidation Controlling Gases in the Greenhouse resulting in the destruction of chlorophyll and the Carbon Dioxide (CO2) – The closed environment of bleaching of the leaves. High light can also promote the greenhouse creates a unique opportunity to excessive or evaporative loss of water monitor and modify carbon dioxide levels during from the leaves, which results in wilting and drying crop production. During the winter when the of the leaves. This can be prevented by hanging greenhouse is closed all day, CO2 levels may drop mesh shade cloth from eave to eave, or by applying a below the ambient concentrations of 300 to 360 ppm whitewash to the greenhouse covering. A 30% to due to plants using the CO2 for photosynthesis, and 50% shade is commonly used. due to no fresh air coming into the greenhouse to replenish the CO2. CO2 can become a limiting factor Controlling Daylength for Floral Induction and for plant growth under these conditions. CO2 Initiation – Daylength is the length of the light and injection into the greenhouse, referred to as CO2 dark periods in a growing situation. Daylength can fertilization, can enhance and hasten vegetative plant be a controlling factor for flower induction and growth and flowering. Plant growth can be enhanced initiation for many plants. Plants that are by increasing CO2 up to 1200 to 1500 ppm during photoperiodic can be induced to flower with one closed greenhouse conditions. photoperiodic Daylength, and the opposite Daylength will keep them vegetative. Plants should grow Ethylene (C2H4) – Ethylene is a water soluble gas and vegetatively to a desired size prior to inducing and a natural occurring which is produced initiating flowers on the crop. in , , flowers, stems, leaves and . Ethylene controls a multitude of plant responses as Long Day (LD) light regimes can be created by: (1) described below. When fuel sources of high purity using natural long days, or (2) using Night- are combusted in the presence of adequate oxygen, interruption Lighting (NI). NI is created by only CO2 and water vapor are produced, however, exposing plants to at least 10 to 15 foot-candles of this type of complete combustion rarely exists. By- light via incandescent or high intensity lights from products of incomplete combustion include ethylene 10:00 PM to 2:00 AM. This makes the plant react to gas which can be injurious to plants. short dark periods which provides the same effect as long days. Growers can put the lights on a timer or Plants exposed to external ethylene sources such as have the lights controlled through a computerized exhaust from vehicles or improperly vented heaters, environmental control system. will frequently exhibit the Triple Pea Response, which consists of: Short Day (SD) light regimes can be created by: (1) 1. Dwarfing. using natural short days, or (2) during natural long 2. Stem Thickening. days, create Short Days by covering plants with 3. Epinasty. Blackout Cloth. The Blackout Cloth must hang to Epinasty is the curling of stems, petioles and leaves. the ground so no light reaches the plants. If the External ethylene can also cause abortion, Blackout Cloth covers from gutter to gutter in a ripening of , and senescence of plant parts. greenhouse, the fans should run to prevent heat Concentrations of 0.1 ppm for 24 hours can injure a buildup under the Blackout Cloth. High temperatures plant. Exposure to ten ppm for a few hours can kill a under the Blackout Cloth can cause hard growth, plant. chlorosis, malformed flowers, delayed flowering, and bud abortion. Opening the Blackout Cloth from Air samples can be sent to a testing lab for ethylene 11:00 PM to 2:00 AM may also help prevent heat detection. Heaters should always be vented to the accumulation under the Blackout Cloth during high outside and have adequate venting for complete temperature periods in the summer. Blackout Cloth combustion. Avoid running motors that run on is sometimes pulled during natural Short Days to carbon based fuels in the production area. prevent stray light from reaching the crop during required dark periods. There are many reported cases Irrigation of Greenhouse Crops where stray light from security lights or automobile Water Quality – It is important to know the chemical traffic shine into the production green houses and content of the water used for greenhouse irrigation

43.2-7 0510 regardless of its source. Soil testing labs will also wide pH ranges while many grow best at pH levels analyze water samples. below 6.0.

A water quality test should include a soluble salts To counter the potential affects of cumulative test which is measured with an Electrical alkalinity on medium pH, growers may utilize the Conductivity (EC) meter and is reported in following procedures. mmho/cm. It measures all electrically charged ions dissolved in the water. The more dissolved solids in 1. Use acidic residue fertilizers. the water, the greater the electrical conductivity which equals a higher soluble salt reading. The 2. Use less lime in the preplant pH adjustment and upper acceptable EC level of irrigation water for fertilizer program. seedlings is 0.75 mmho/cm and for older crops is 1.5 mmho/cm. Salts from irrigation water can 3. Use acid injection in the irrigation lines. accumulate in the growing medium and cause plant injury if they are excessively high. Monitoring 4. Use a reverse osmosis filtering system. soluble salts should be a routine part of any fertility program for containerized or container-grown plants. Injection of nitric acid, phosphoric acid or sulfuric acid into the irrigation lines is done with a The alkalinity of irrigation water is critical in commercial fertilizer injector to bring the water pH controlling medium pH. Alkalinity is the down to a 5.8 pH. At a pH of 5.8, bicarbonates are Milliequivalents of carbonate and bicarbonate per bicarbonates are broken down to water and carbon liter of water. It is reported as Milliequivalents per dioxide. The amount of acid needed to lower the liter of water (Me/L) of equivalent of calcium alkalinity is dependant on the original and desired carbonate. Low levels of alkalinity, 1.0 to 1.5 Me/l alkalinity, and the pH of the water. North Carolina are desirable for irrigation water. At this level, the State University has an alkalinity calculator on the effects on growing medium pH are manageable. internet at www.floricultureinfo.com. Click on Floriculture Software. When the water alkalinity is greater than 1.5 Me/L, the growing medium pH begins to rise. As water is High alkalinity is often accompanied by high applied to the medium, the carbonates and Calcium (Ca) and Magnesium (Mg) in the water. bicarbonates in the alkaline water combine with the Water hardness, reported as Milliequivalents per hydrogen ions (H+) in the medium. This chemical liter of water (Me/L) of equivalent calcium reaction forms carbonic acid (H2CO3) which breads carbonate, is a measure of combined Ca and Mg in down into water (H2O) and carbon dioxide (CO2). the water. It is important to recognize that alkalinity The H+ ions extracted from the medium by alkaline and hardness are not identical. An imbalance in the water, results in a rise in the medium pH, since pH is Ca and Mg levels can result in nutrient deficiencies a measurement of H+ ion concentration. of one or both of the nutrients. A Ca:Mg ratio of 3 to 5 Ca:1 Mg should be maintained. When the growing medium volume is small, as in a It is wise to have a water test done every few years plug tray, alkaline water can increase the medium and during unusual water events such as drought or pH very quickly, even in a matter of a few days, as flooding periods as they can alter water quality. For there is not much medium to buffer the reactions. additional information please refer to Chapter 28, Cumulative quantities of carbonate and bicarbonate . can increase in the medium over time with consecutive irrigations of crops. If the length of the Under Watering – When water is not applied crop cycle is short as such as with a three- to four- frequently or in adequate quantities, the plants will week Marigold crop, the cumulative affect may not have a hardened appearance. Under watering reduces be a significant. If, however, the crop cycle is longer, photosynthesis and overall growth. In addition, the for example a 12-week Chrysanthemum crop, the elongation of young cells is reduced, resulting in cumulative affect may be quite significant and may smaller leaves and shorter stem internodes. In severe warrant some method of intervention or control. cases, wilting, marginal leaf burn, dry patches on the How tolerant a crop is to increased pH levels will leaves and death may result. also vary by plant species. Some crops will tolerate

43.2-8 0510 Over Watering – Applying water too frequently or in when it is dry to a dept of the middle knuckle, it is excessive quantities will keep the soil pores filled time to irrigate. with water which reduces oxygen availability to the roots resulting in a weaken root system. High water 4. Select the Proper Time of Day to Irrigate content in the growing medium may produce large Irrigate so that the plants are turgid and remain leaves, but they will be soft and succulent, which turgid during the heat of the day, which is usually makes them susceptible to high temperatures and from 11:00 AM to 2:00 PM. Avoid irrigating at a high light stress. Over watered plants can wilt due to time which would leave the plants wet over night. lack of oxygen in the growing medium. They can also have excessively long internodes, chlorotic 5. Keep the Leaves as Dry as Possible lower leaves, soft growth, and are more susceptible to A film of water on the leaf surface creates an nutrient deficiencies. It is important to let the environment conducive to disease development, growing medium dry to 40% to 60% of its original especially when going into the cooler, darker weight before re-watering. This will allow oxygen to evening and night hours. Irrigation systems that reenter the medium, as oxygen is required for root minimize leaf wetting will help control diseases. development. It takes much longer for a plant to Water early in the day so the leaves have time to recover from over watering that from under watering. dry before darkness to minimize disease Therefore, it is better to error on the side of growing development. plants slightly dry. 6. Adjust Irrigation Relative to the Environment Best Management Irrigation Practices – Best Adjust the frequency of irrigation as changes in Management Practices (BMP) for greenhouse the environment occur. This includes light irrigation includes, but is not limited to the following: intensity, temperature, air movement and humidity. Many irrigation systems are integrated 1. Use a Well Drained Growing Medium with computerized environmental control systems For additional information, please see the that automatically monitor environmental Growing Media section of this chapter and also conditions and adjust the irrigation accordingly. Chapter 41, Container Production. Conditions that increase the plant’s use and transpiration of water will require the frequency 2. Water Thoroughly of irrigation to increase; the reverse is also true. The root zone should be entirely wetted each time For example, with four to five consecutive days of a plant is watered. Recommendations include cloudy weather, plants may not need to be creating a 10% leachate with each irrigation to watered at all, depending on temperature. Over ensure saturation, and to minimize soluble salt watering during cloudy weather can lead to soft accumulation. Many alternative irrigation growth plus physiological and pathological techniques are available to ensure thorough problems. watering, yet minimize water run-off. Growing Media for Greenhouse Crops 3. Water Just Prior to a Moisture Stress Level A growing medium for container greenhouse crops Never wait to irrigate until the plant wilts. All requires a good water holding capacity as well a good plant species differ in their water requirements. aeration and drainage. For information on water Signs that a plant is approaching water stress holding capacity, porosity and characteristics of include loss of luster of the leaf surface. Plus, a container growing media, please refer to Chapter 41, subtle change in leaf color occurs, becoming a Container Production. In addition, specific attributes bluer or grayer shade of green. The color of the of media components for greenhouse production are growing medium may also be used to evaluate the discussed below. irritation status. Pear-based media and most other media, become lighter tan as the medium dries. Peat – Sphagnum peat and Hypnum peat are the most The weight of the growing medium can also be commonly used types of peat in the greenhouse. The used to gage irrigation requirements. Allow high water holding capacity of peat is created by the plants to dry down to 40% to 60% of its original many small capillary pores created by many small water weight before re-watering. Using the peat particles. Peat increases water holding capacity. “Finger Test” on container crops can also be used. Good drainage and gas exchange occurs in peat only Insert the pointer finger into the medium and if it is a very coarse peat, therefore, peat with large

43.2-9 0510 particles is preferable to finely ground peat. well and is used in propagation media for that Sphagnum peat is more coarse and has a lower pH purpose. It does compact over time, therefore, it than Hypnum peat. The pH of Sphagnum peat ranges should be used on short term crops like bedding between 3.0 and 4.6, therefore, dolomitic lime is plants rather than in longer term crops. Vermiculite generally added to peat-based media to raise the pH has no affect on medium pH. to 5.8 to 6.2. Peat particles are naturally hydrophobic, however, adding a wetting agent and/or Sand – Sand can be very fine textured or it can using warm water will aid in wetting the peat. consist of larger particle sizes. Only sand with large particles size will improve aeration and drainage and Composted Bark – Composted softwood bark and it must be used at over 25% of the medium volume. hardwood bark are good organic media components It is heavy, therefore it has limited use in greenhouse that are less expensive than peat. Thermophyllic crops which need to be transported to market. The micro-organisms sufficiently heat the composting added weight can increase shipping cost and be a bark and render it essentially pasteurized. The large disadvantage in handling. Sand particles have very particle size of bark chips promotes good drainage. little water holding capacity and sand can increase A bark-based medium is drier compared to a peat- medium pH. based medium. If a grower over waters a bark-based medium it is not as critical as it would be in a peat- Hulls – Composted rice hulls are another based medium. Bark media may tie up some alternative organic medium component. They can chemicals including growth regulators and vary from large full rice hulls to a finely ground that are applied as drenches. Avoid chemical product. Coarse rice hulls enhance the aeration of a drenching these products when bark is a major medium and finely ground rice hulls enhance the component in the medium. water holding capacity of a medium. It is wise to re- evaluate watering practices when first starting to Coir – Coir is derived from ground coconut husks grow in a medium containing rice hulls. Rice hulls and has the consistency of a fibrous semi-coarse peat. have a minimal impact on medium pH. It is functions similar to peat and it can be used as an equivalent substitute for peat or as an addition to Rockwool – Rockwool is derived from basalt rock peat. It is slightly better aerated than peat and it wets that is pulverized, heated and spun into fibers like more readily than peat. It has a pH of 4.9 to 6.8. cotton candy. Slabs of Rockwool are used in Plants grown in coir have enhanced rooting compared hydroponic production, whereas granular Rockwool to other media. This may be due to natural hormones is used in container production. Rockwool has no found in the coir. Therefore, coir has become a impact on medium pH or Cation Exchange Capacity. popular component in rooting media. It has good water holding capacity, therefore, it is added to crops that require frequent irrigation such as Perlite – Perlite is derived from a volcanic mineral hanging baskets. A 1 Peat:1 Rockwool mixture that is heated and popped like popcorn into puffy, makes an excellent growing medium. white porous particles. The large particle size provides good medium aeration and drainage. It Preferred properties of a growing medium for holds up well and does not affect the pH of a greenhouse crops include the following: medium. Perlite may release some fluoride which can cause tip burn on monocot plants. As a 1. Well drained and well aerated, but still have good precautionary measure, limit the use of perlite in water holding capacity. media used for monocots such as Lilies and Cholophytum. Perlite has been used successfully in 2. Bulk density of 0.4 to 0.6 g/cm2. long term crops including many foliage plants. 3 A pH of 5.4 to 6.2 for Soilless media, and 6.2 to Vermiculite – Vermiculite is derived from a mica- 6.5 for soil-based media. like mineral and is heated and popped like popcorn to form light weight, golden, layered particles. 4. A minimum of 15% to 20% air by volume for Vermiculite is graded according to particle size with container crops. the Grade being relatively fine compared to regular Horticultural Grade in which the 5. High nutrient holding capacity of 6 to 15 particles are much larger. Vermiculite holds water Me/100cc.

43.2-10 0510 6. Pre-plant slow-release phosphorus fertilizer according to dimension and volume in both U.S. and incorporated to promote early root development. metric terms. For additional information, please refer to Chapter 48, Marketing, Merchandising and Sales. 7. Dolomitic lime incorporated to adjust pH. Plastic has been the dominate container material in 8. Micro-nutrients incorporated to supply minor the industry. Recycling programs should be used to nutrients for the crop duration. minimize the contribution of plastics in the stream of waste products. New types of biodegradable 9. A wetting agent to counter the hydrophobic nature container materials are becoming more available on of peat. the market in response to industry pressure for more “green’ and sustainable alternatives to plastic. Growers are almost exclusively using Soilless media for greenhouse crops. Various combinations of the Germination and Development of Plugs above described components are prepared by The germination of seeds in plug trays, where each individual growers, or they purchase pre-mixed is placed and grown in its own cell, has media which are also adjusted to each grower’s revolutionized the bedding plant and vegetable specific growing conditions and crops. transplant industries. Plug production is divided into four stages from germination to transplanting for the The depth of the container that a crop will be grown ease of specifying optimal levels of environmental in, and the moisture preferences of the crop, greatly and growing medium factors during production. influence the type of growing medium that should be Optimal environmental conditions and growing used. If grown in open benches or beds, cut flower medium requirements change as the plant transitions beds require a growing medium of seven inches. from one stage of development to the next (Table 1).

Containers for Greenhouse Production Production Stage 1 is frequently accomplished in The bedding plant industry has used the 1020 Flat as growth chambers or tight greenhouses where the industry standard for many years. It is a flat that humidity levels are high and temperatures are warmer is 22 inches wide by 21 inches long. A sheet of than most growing temperatures. Light and fertility bedding packs that fits into a flat is referred requirements increase as seedlings develop, while the to as an insert. The inserts are composed of a series temperature and moisture requirements decrease over of individual packs with a various number of cells per the same time period. The overall strategy in pack. The inserts are specified by a set of four producing quality plugs is to develop a strong root numbers: the first two numbers specify the number of system, while restricting shoot growth. In addition to packs per flat and the second two numbers specify the environmental condition, the type of fertilizer the number of cells per pack. For example, a 1206 influences the type of plant growth achieved. High flat has 12 packs per flat with 6 cells per pack; a 3201 NH4 and excessive P will promote shoot growth and excessive stem elongation, while high NO3 and Ca, flat has 32 detachable packs with a single cell and moderate P, will promote root development and composing the pack. There are some suppliers maintain a toned plug. Negative DIF and growth experimenting with smaller cell sizes to increase the regulators are also effective in controlling plant number of plants produced per square foot of bench height of many plug species. space. This is an economically based incentive, not one based on plant growth. To offset the smaller cell Plugs should be transplanted into a moist medium as dimensions, deeper cells are used so the root volume soon as possible once they reach an appropriate size remains somewhat constant. Deeper cells and and before they become root-bound. Plugs held too containers provide better drainage and are often use long in the plug tray will have delayed growth after as part of a water management strategy. transplanting. Several references are available for achieving optimal growing conditions during plug Many floriculture products are grown in 2.5-inch, 4- production for individual plant species. inch, 5-inch and 8-inch containers which are moved by using plastic molded shuttles or carrying trays. Seed Enhancements Larger specimens and hanging baskets of 10-inch or Plug growers have encouraged seed companies to 12-inch diameter or larger are also common in the develop seed enhancements to improve the percent trade. Containers in the retail setting must be labeled germination in order to achieve a consistent 100%

43.2-11 0510

Table 1. Plant development as influenced by environmental factors and growing medium requirements during the four stages of plug production.

Plant Development Stages

1 2 3 4

Seed Imbibes Stem and Growth and Plants Ready Plant Development Water, Cotyledons Development for Stage Description Radical Emerge of True Transplanting, →→→→→→→→ Emerges Leaves Shipping or Bedding

Factors Affecting ↓ Plant Growth ↓ Optimum Condition of Environmental Factors and Growing Medium Requirements

Moisture High High to Moderate Low Moderate

Temperature 70 to 80o F 65 to 78o F 62 to 70o F 60 to 68o F

Light Low Low High High 1500 Ft-c. 1500 Ft-c. >1500 Ft-c. >1500 Ft-c.

Fertility Not 50 to 75 50 to 100 100 to 150 Applicable ppm NO3 ppm NO3 ppm NO3

stand of vigorous seedlings and for the precise pre-germination, the germination process is allowed placement of the seed in the planting medium. A full to progress to the point that the radicle, or young seedling stand is important for sales as well as for root, starts to protrude from the seed. Hydrated seeds efficiency in automated transplanting. Enhanced are more delicate and have a more limited shelf life seed is frequently more costly and growers should than regular seed because the metabolic events evaluate the benefits against the higher cost given leading to germination have been initiated. specific production goals. Therefore, hydrated seed needs to be used within a short time of purchase. Seed suppliers will Seed Hydration – Seed hydration treatments promote recommend proper handling and storage procedures water uptake by the seeds to start the early for the seed purchased. physiological events of germination. The seed is then re-dried prior to shipping to the grower. Pre- Pelletized Seed – Mechanical seeders are used to hydration, priming, matri-conditioning, and pre- precisely drop seeds into plug cells. The ability of germination, all use hydration to increase the rate of the seeder to pick up the seed and place it as close to germination and uniformity of the seedling stand. In the center of the cell is difficult with some raw seeds

43.2-12 0510 due to the shape, size or other seed characteristic. of the plant decreases compared to the darker side of For example, Begonia seeds are extremely small, the stem. Hence, the stem cells on the dark side have tomato seed has a layer of fuzz that causes it to stick more auxin and elongate more than those on the to surfaces, and Marigold seeds are very long with a lighter side. This results in non-uniform growth of papus tail. Therefore, tomato seed is de-fuzzed and the cells within the stem and the bending of the stem Marigold seed is de-tailed prior to sale. Pelletizing is towards the light. When seedlings are grown under a process that adds a substance to the outside of small low light, the high auxin concentrations cause rapid or irregular shaped seeds that will make them larger stem elongation. As the seedlings are moved into and more round in shape for easier seeding. Species higher light intensities, the light destroys the auxin that have small, fine textured seedlings such as and the rate of elongation slows. Lobelia, Alyssum and Portulaca, are multiple seeded. Pelletizing three to four seeds together into one pellet Auxin also inhibits the growth of lateral or axillary greatly improves the consistency of multiple seeding. buds. This is known as Apical Dominance. Auxin Pellets vary in composition, so growers may need to is synthesized in the apical stem tip and in the newly adjust misting rates during germination to ensure formed unexpanded leaves and is translocated water imbibition into the seed. downward in the phloem to other plant parts including the axillary buds. High auxin Seed Coating – Seed coatings are substances applied concentrations in the axillary buds inhibits the buds to the outside of the seed to enhance seed from growing. Cytokinin, another plant hormone, is performance. These substances include , synthesized in the roots and moves through the xylem insecticides and micronutrients. Film coatings are a to other plants parts including the axillary buds. thin layer natural or synthetic polymers applied as a Cytokinins promote the growth of axillary buds. liquid to the outside of the seed. They frequently Therefore, the balance of auxin to cytokinins in the have a colorant that enhances the visibility of the axillary buds determines if the buds will grow. When seed during . Some films will smooth the a plant’s terminal branch is pinched, which removes outside texture or decrease the static electricity on the the apical stem tip and the young unexpanded leaves, outside of the seed which facilitates the seed flowing the natural source of auxin is also removed. through the seeding equipment. It is possible to have Consequently the auxin concentration in the axillary several layers of film coatings on a seed, each with a buds goes down, while the cytokinin concentration different benefit. Insecticides or fungicides can be remains constant and hence, the balance of auxin to included in film coatings. cytokinin in the axillary buds is altered and buds are promoted to grow. . Growth Regulators for Floriculture Crops Auxin also initiates the formation of adventitious Plant growth regulators or PGR’s, are used to block, roots. Commercial rooting hormone products contain interfere, modify or enhance plant responses that are the natural auxin Indoleacetic Acid (IAA), or the normally controlled by natural plant hormones. synthetic auxins including Indolebutyric Acid (IBA), Understanding how the main five categories of Naphthaleneacetic Acid (NAA). These products can natural occurring plant hormones impact plant be applied to the base of cuttings as a thin film of growth is necessary when selecting the appropriate powder. They can also be dissolved in alcohol and PGR for a specific use. Plant hormones are naturally diluted with water to a final concentration between found in a plant, whereas, PGR’s refer to materials 200 to 5,000 ppm, and then cuttings can be dipped or applied externally to the plant. Plant hormones may soaked in the solution. This method enhances the also be PGR’s. The five naturally occurring Plant permeability of the solution into woody stem . Hormones are described below. Gibberellic Acid – There are many formulations of Auxin – A major role of auxin is to promote growth Gibberellic Acid (GA) in plants. Gibberellic acid through cell enlargement. Stem tips and associated promotes plant growth by stimulating cell division expanding leaves are primary locations for auxin and enlargement. Internode elongation is attributed synthesis. Auxins are translocated down the stem. to Gibberellic acid. Pillar Geraniums are frequently Auxin is involved in tropistic growth movements sprayed with Gibberellic acid to promote internode including the downward growth of roots, the upward elongation which creates a taller plant. growth of , and the bending of the plant Soaking seeds in Gibberellic acid enhances towards light. Auxin is inactivated by blue light, germination in some species. It also promotes floral therefore, the auxin concentration on the lighter side development in some herbaceous species.

43.2-13 0510 Commercially this has been used on Cyclamen, needs to be avoided. Diseased and dead leaf Spathiphyllum and Statice to reduce the time to litter can also release significant levels of ethylene. flower. Plants stored or shipped in boxes and/or plant sleeves can accumulate ethylene in the shipping packaging Cold temperatures promote the development of resulting in severe plant injury. Examples of Gibberellic acid in plants. During the winter, deleterious post-harvest exposure to ethylene include: Gibberellic acid is formed in the tulip which flower bud abscission in Thanksgiving Cactus and then elongates the floral stem in the spring. Hibiscus, epinasty of Poinsettia petioles, flower Commercially, Gibberellic acid is used to substitute closing in Kalanchoe, and leaf yellowing and flower for the cold requirement needed to break bud shattering in Geraniums. Proper ventilation, dormancy in some woody species. For example, avoidance of repining or senescencing plant material, dormant buds can be stimulated to grow by cooler temperatures, and the use of potassium applying a series of Gibberellic acid sprays to replace permanganate filters are possible means to limit the cold treatment normally needed to overcome ethylene damage during shipping. dormancy. Pro-Gibb is a liquid formulation of Gibberellic acid and Gibb-Tab is a tablet formulation, Silver thiosulfate (STS) and Ethyl-Bloc are both are used as Plant Growth Regulators (PGR’s). compounds that inhibit ethylene synthesis in the plant. STS can be sprayed on Geranium blossoms Cytokinins – Cytokinins promote cell division and when they show 25% color. STS can also be used in stimulate shoot formation in plants. Cytokinins also the holding water of cut flowers to extend vase life. delay leaf senescence and reduce leaf yellowing in Ethyl-Bloc is a gaseous compound that is also used in cut-flowers including cut Asiatic lilies and potted cut flower post harvest applications by wholesalers Easter lilies. Synthetic cytokinins, such as Accell and retailers to block ethylene production. and Promalin, are formulations of benzyladenine and are used as Plant Growth Regulators (PGR’s). Ironically, ethylene also produces several beneficial effects on plants, of which several are used Abscisic Acid – Abscisic Acid (ABA) is involved in commercially. Ethylene in its gaseous form is hard dormancy, abscission and stomatal closing in plants. to apply, however, Ethephon, a liquid form is sold as It is starting to be used commercially to control these Ethrel and Florel. Upon spraying these products on a plant functions. plant, ethylene is produced inside the plant tissue. Uses of Ethephon include the following: Ethylene – Ethylene (C2H4) is a water-soluble gas that is naturally produced by all plants. There are 1. Promote flowering in Bromeleaceae. desirable and undesirable plant responses to ethylene. Ethylene is known as the “Ripening Hormone” as it 2. Abort early flowers on New Guinea Impatiens. promotes ripening of fruits as well as senescence of flowers and other plant parts. Ripe fruits and plants 3. Defoliate Hydrangeas prior to cooling. under stress release increased levels of ethylene. Injured plants and plants bending and swaying in the 4. Manage height control in bedding plants. wind also release ethylene as a “wound response”. Ethylene released from moving plant parts causes a 5. Increase the number and uniformity of branching stem thickening and dwarfing response. This is on herbaceous crops. noticeable in un-staked in the nursery as well as in plants on the edges of greenhouse benches where Many growers pinch Poinsettias, Mums or the leaves are constantly rubbed or touched. Geraniums, and then 24 hours later, spray with Ethephon to improve the branching of the crop. Avoiding the deleterious effects of ethylene is a major concern in floriculture. Ethylene can cause Growth Retardants leaf, bud and flower abscission, epinasty, early Growth Retardants are chemicals used to decrease flower senescence, and leaf yellowing. Ethylene internode elongation on a wide range of floriculture build-up exposure during shipping is of great crops to create a tighter plant with an improved visual concern. Shipping or storing floriculture products plant form or structure. Many are anti-gibberellic with fruits should always be avoided. The exhaust acid agents. Growth retardants do not decrease the from vehicles is another major source of ethylene that number of leaves, they decrease the internode length.

43.2-14 0510 Therefore, the primary response is reduced plant B-Nine – B-Nine (Daminozide, B-9) is only applied height. Several Beneficial side-effects have been as a spray as it is very mobile in the plant after documented with growth retardants including: application. It is applied at 1,200 to 5,000 ppm from either a Liquid or Wettable Powder formulation. B- 1. Greener leaves or increased chlorophyll. Nine requires 12 to 24 hours to be absorbed into the plant, therefore, it is important not to wet the leaves 2. Thicker epidermal layers. again for 24 hours after application. B-Nine is effective on a wide range of plants, however, it has 3. Increased resistance to insects. little to no effect on Impatiens, Coleus, Pansy, Snapdragons, Geraniums and Lilies. 4. Lower transpiration rates. Cycocel – Cycocel (Chlormequat, CCC) is available 5. Increased . as a liquid and can be either sprayed on a plant, or used as a growing medium drench. Spraying is 6. Increased frost tolerance. generally less expensive. Cycocel is commonly used to control plant height of Poinsettias, Geraniums and 7. More rapid flowering in some species. many bedding plants. Sprays can result in yellow blotches or chlorotic margins on the leaves 24 hours 8. More toned plant growth. after application. This is temporary and the plant will grow out of it. This condition is known as “Cycocel Growth retardants and other PGR’s should be applied Burn”, but it should not be a long term issue. to dry leaves of non-stressed plants. Some products Combinations of Cycocel and B-Nine have a are not as effective under high temperatures, synergistic effect and can be tank-mixed for more therefore, morning or late afternoon applications may effective control than either product would provide be more effective. Applying sprays under conditions alone. that allow the plant to stay wet longer will also aid in the uptake of many products. These conditions occur A-Rest – A-Rest (Ancymidol) is a liquid that can be during higher humidity periods, cloudy weather, low applied as a spray or drench depending on the crop. air movement and cooler temperatures. Drench A-Rest is one of the more effective growth retardants applications to the growing medium are frequently on monocot plants. Dipping or Easter lily effective, however, composted bark ties up some bulbs in A-Rest for 30 minutes after the cold growth retardants, therefore, if the medium contains treatment, but prior to planting, works well to control bark, a spray application should be used. When stem elongation in potted plants. A-Rest sprays can applying a spray, uniformly wet the plant just to the cause phytotoxicity resulting in necrotic spots on the point of runoff. The volume of product required for a leaves. This is more likely to occur when the drench versus a spray may vary considerably and can temperature is above 70o F. Poinsettias have shown substantially affect the ultimate cost of application. sensitivity to A-Rest.

Apply growth retardants prior to the stretching of the Bonzi – Bonzi (Paclobutrazol) is very active at low plant. Plants growing under cooler conditions require concentrations in almost all plant species. Bonzi is less growth retardants than similar plants under only translocated in the xylem, not in the phloem. warmer conditions. Northern growers generally use Therefore, the product only moves upward in the fewer applications and lower concentrations plant. Drenches are effective as are sprays that apply compared to southern growers. Likewise, a northern the product to the stem rather than the leaf tissue. grower may experience different crop responses from Growers need to be careful not to over-apply Bonzi year to year based on differing natural weather as excessive concentrations result in long term conditions. recovery times to normal growth. Bonzi as a drench on plugs at the time of seeding for long term height Although several growth retardants are available on control is being experimented with. the market, five of the most common are described below. Not all growth retardants are effective on all Sumagic – Sumagic (Uniconazole), like Bonzi, plants. Read and follow the label, and check for belongs to the chemical group classified as triazoles. use on specific plants and for appropriate Triazoles are very active in almost all plant species. concentrations for the intended use.

43.2-15 0510 Sumagic can be applied as a spray, drench or a dip bedding plants and flowering potted plants. Low for cuttings or bulbs. temperature toning is not used on foliage plants. Toning with low light conditioning is restricted to Other PGR’s – Off-Shoot-O and Atrimmec are foliage plants and is essential in ensuring foliage will chemicals that terminate shoot growth and can, adapt to lower light conditions experienced in the therefore, be use as chemical pinching agents. The consumer setting. Lowering the light intensity for six growth of the terminal shoot is inhibited, which then weeks to six months, depending on size and plant causes the lateral buds behind the terminal to grow species, at the end of foliage production greatly because the Apical Dominance has been removed. reduces chlorosis and leaf drop in post production settings. Post Production Handling Shelf Life refers to the post production period for Shipping – Plants should be moist, but not wet at the containerized or container-grown plants, and Vase time of shipping. Excessive moisture creates a Life refers to the post production period for cut humid environment which encourages the flowers. The retention of product quality and development of Botrytis in the confined conditions of ultimate longevity of a product in the post production closed boxes, sleeves, trucks and coolers. Ethylene setting is directly correlated to the chain of conditions can also cause post production injury. Symptoms extending from early production, through harvest, include leaf chlorosis, bud and flower abscission, and to holding, shipping, and retail sales. Healthy epinasty and potential overall plant decline. Ethylene plants will hold up better in post production. build-up can occur due to normal plant release of Therefore, providing optimum light, temperature, ethylene in confined areas. Bending and bruising of fertility, water and CO2 during production is the first foliage during Sleeving and handling will release step in maintaining quality throughout the sales ethylene, as will decaying plant parts, exposure to period. ripe fruits, and exhaust from vehicles and engines. All precautions should be taken to minimize exposure A compact plant is less susceptible to to ethylene. Minimizing the time a plant is in a mechanical damage during movement through the sleeve is also important. Sleeved Poinsettias generate market channels. Negative DIF and/or PGR’s are significant ethylene and, therefore, experience tools available to growers to develop compact plants epinastic leaves, chlorosis and droopy if kept in addition to selection, and to cultural in the sleeve more than a few hours. Venting and management through environmental control. Plants providing adequate air circulation in the shipping that are toned at the end of the production period are containers and storage rooms will help control also less susceptible to temperature, water and ethylene build-up. STS as a spray and Ethyl-Bloc as mechanical stresses during shipping and marketing. a gaseous treatment applied prior to shipping can Toning is achieved by providing less than adequate minimize ethylene evolution from plants. Ethylene light, water, heat and/or fertilizer at the end of production and the plant’s sensitivity to ethylene will production to create a temporary reversible stress on decrease as temperature decreases. Maintaining the plants. The industry refers to this process as temperatures as low as tolerated by the plant without hardening off. Reducing or even stopping causing injury during shipping has multiple benefits. fertilization for one to two weeks prior to shipping, Low temperatures will limit ethylene damage and frequently improves the quality and shelf life of a decrease respiration rates, which conserves the plant for the consumer. During production, frequent carbohydrates in the plant. Most bedding plants and watering keeps the internal water content of the plant potted flowering plants can be shipped at high, resulting in “soft growth”. Soft plants wilt temperatures in the range of 40o to 60o F. Cold- readily when exposed to the stress of drying winds, sensitive plants such as foliage plants and Poinsettias high temperatures, high light intensity, and should not shipped at temperatures below 50o F. insufficient watering, all of which can occur during Darkness and low light during shipping can cause shipping and retail display. Reduced watering during chlorosis, leaf drop, floral bud abortion, and the last few weeks of production, will develop harder, stretching of plant parts. Unfortunately, providing more toned plant growth which will have a greater light during shipping is generally not possible. tolerance to environmental and mechanical stress Typically, green plants can tolerate seven days of during post production. Lowering the temperature by darkness and bedding plants tolerate approximately five to ten degrees F after the flower buds are visible, two days of darkness provided precautions are taken will also tone plants and this practice is used for to control the temperature.

43.2-16 0510 Vase Life of Cut Flowers – Vase life of cut flowers is 1. High transpiration rates resulting in excessive dependent on many variables. The time of day for water loss. harvesting cut flowers can greatly influence the longevity of some species. Flowers accumulate 2. Plugging of by air, bacteria, or carbohydrates during the day via photosynthesis and chemicals exuded by the plants. then during the night, carbohydrates are consumed through respiration. Therefore, a flower harvested in 3. Presence of disease organisms including late afternoon will frequently have greater Botrytis. carbohydrate reserves and have a longer vase life than one harvested in the morning. Immediately after 4. Insufficient carbohydrate supply to support harvest, cut flowers should be cooled to remove the respiration. field heat from the plants. 5. Exposure to ethylene. The market chain is the chain of life for fresh flowers. It includes the time from producer to Commercial floral preservatives have been developed wholesaler to retailer to consumer. Keeping flowers to combat these potential problems. The four major cool throughout the chain of life is essential to extend ingredients in a preservative are as follows: vase life longevity. Storage and shipping temperatures of 35o to 40o F are appropriate for most 1. Acidifier – Maintains cell fluid pH for normal cut flowers. Sensitive tropical flowers, including the metabolic functions and promotes hydration. Orchids, should not be held below 50o F or they will show browning. Cut flowers are shipped in 2. Carbohydrate – Sucrose or fructose that serves as cardboard boxes lined with foam, plastic sheeting a substrate for respiration. and/or newspaper for insulation . The boxes should 3. or Bactericide – Prevents stem have holes in the sides for ventilation to prevent plugging from diseases. ethylene build-up in the box. When flowers arrive at a storage facility or retailer’s 4. Respiration Inhibitor – minimizes respiration cooler, the flowers should be hydrated and placed in rates. preservative as soon as possible. Hydration, the uptake of water into the stem and flower head, is Floral preservatives should be used in all steps promoted by maintaining a pH of 5.2 to 5.8 in the throughout the chain of life including having the holding solution. This pH closely equates to the pH consumer add it to their holding water. of the cell fluid in the plant. Citric acid is used to acidify the holding solution. Warm water at 70o to Good sanitation practices during post production 110o F will also aid in hydration. handling and shipping will help reduce incidence of ethylene and disease exposure. Refrigerator holding Flowers that have been held dry for any length of containers should be sanitized at least once per week. time will need to have the stems re-cut to remove any Plant debris should always be removed immediately potential air blockage at the base of the stem. The from the storage area. xylem vessels in the stem are like a series of straws. When water evaporates from the xylem cells at the Crop Scheduling base of a cut stem, air replaces the water . Scheduling a crop is the most fundamental part of a The capillary action is interrupted and the water production program. Creating a road map for molecules are sufficiently large so they cannot move production will aid in ordering supplies, optimizing around the air in the xylem resulting in a lack of space utilization in the greenhouse, fine tuning water uptake and subsequent premature death of the environmental conditions, meeting target market flower. Remove one to two inches of stem tissue to dates, plus predicting and optimizing production eliminate the blockage. Cut the stem at an angle to numbers and profits. One of the main goals in ensure that the cut surface does not rest flat on the scheduling should be to increase the number of crop bottom of the holding container as this would prevent turns in the operation. This refers to the number water uptake. consecutive crops produced in the same production area in a given period of time. Vase life decline can be caused by following conditions:

43.2-17 0510 Creating a production schedule or plan requires a expenses are those that are directly incurred by grower to develop a detailed schedule for the major growing a specific crop including propagules, crops produced. To facilitate implementation of all containers, growing medium, fertilizer and all other the schedules when there are a large number of expenses. Comparing the total expenses to the actual varieties or minor crops involved, it is preferred to revenue will determine the profitability of each schedule no more than five scenarios per greenhouse specific crop. turn or per grower. Compare growth and development requirements across the crops to be Successful growers will know which crops are more grown and group them by similarities. profitable and will eliminate crops that operate at a loss. Minimizing the dumpage or percent loss of The schedule or plan should include specific specific crops is also important to the bottom line, environmental conditions that are required to achieve and this must be tracked for each crop. An the steps in plant growth and development. This acceptable loss factor within the industry is no would include temperature, photoperiod, light greater than four percent for most corps. Good intensity and irrigation. The schedule should also record keeping will facilitate management of include timing of germination and propagation, plus expenses and realization of profitability. transplanting, fertilization, and container sizes.

Once the schedule or production plan is established, the second step is to monitor and record the actual implementation steps as well as environmental conditions for plant development. This will comprise the actual production record. A comparison of the actual, to the planned schedule will aid the grower in meeting the required market date. As individual crops fall behind in development during production, the grower can adjust temperature and/or other environmental conditions to get the crop caught up to the schedule.

Poor optimization of space utilization reduces profitability. Growing young plants at the highest density possible for the longest period of time and then finishing plants at a low density for short periods of time, will increase space optimization. Reviewing the production schedule and records will provide guidance in optimizing timing and quality of the crop in subsequent years. Successful strategies can be duplicated and alternative strategies can be developed to overcome problems that did occur.

Financial records are equally important to develop and maintain in order to improve future business practices. A cost analysis should be done for each crop by determining the expenses and revenue allocated to each crop. Fixed expenses should be determined and allocated on a per-square-foot-of- bench area, and assessed to the crop based on the number of weeks it occupied that space. Empty bench space must also be accounted for and expensed to some crop when using this strategy. Variable

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