CHAPTER 7 Plant Propagation

Sexual Propagation ...... 1 Seed ...... 1 Germination ...... 2 Methods of Breaking Dormancy ...... 2 Starting Seeds ...... 3 Seed Requirements ...... 6 Transplanting and Handling ...... 7 Propagation of Ferns by Spores ...... 8 Asexual Propagation ...... 9 Cuttings ...... 9 Stem Cuttings...... 9 Leaf Cuttings ...... 10 Root Cuttings ...... 10 Layering ...... 11 Division ...... 12 Grafting ...... 12 Budding ...... 14 Plant Tissue Culture for the Home ...... 14 Medium Preparation ...... 14 CHAPTER 7 Plant Propagation

Edited and revised by David C. Sorensen, University of New Hampshire Cooperative Extension

Plant propagation is the process of multiplying the numbers of a species, per- petuating a species, or maintaining the youthfulness of a plant. There are two types of propagation, sexual and asexual. Sexual reproduction is the union of the pollen and egg, drawing from the genes of two parents to create a new, third individual. Sexual propagation involves the floral parts of a plant. Asexual propagation involves taking a part of one parent plant and causing it to regener- ate itself into a new plant. Genetically it is identical to its one parent. Asexual propagation involves the vegetative parts of a plant: stems, roots, or leaves.

The advantages of sexual propagation are that it may be cheaper and quicker than other methods; it may be the only way to obtain new varieties and hybrid vigor; in certain species, it is the only viable method for propagation; and it is a way to avoid transmission of certain diseases. Asexual propagation has advan- tages, too. It may be easier and faster in some species; it may be the only way to perpetuate some cultivars; and it bypasses the juvenile characteristics of certain species.

Sexual Propagation Although some seeds will keep for several years if stored properly, it is advisable to purchase only Sexual propagation involves the union of the pollen enough seed for the current year’s use. Good seed (male) with the egg (female) to produce a seed. The will not contain seed of any other crop, weeds, seed is made up of three parts: the outer seed coat, seeds, or other debris. Printing on the seed packet which protects the seed; the endosperm, which is a usually indicates essential information about the food reserve; and the embryo, which is the young variety, the year for which the seeds were packaged, plant itself. When a seed is mature and put in a and germination percentage you may typically favorable environment, it will germinate, or begin expect, and notes of any chemical seed treatment. If active growth. In the following section, seed germi- seeds are obtained well in advance of the actual nation and transplanting of seeds will be discussed. sowing date or are stored surplus seeds, keep them in a cool, dry place. Laminated foil packets help Seed ensure dry storage. Paper packets are best kept in tightly closed containers and maintained around 40 To obtain quality plants, start with good quality degrees F. in a low humidity. seed from a reliable dealer. Select varieties to provide the size, color, and habit of growth desired. Some gardeners save seed from their own gardens; Choose varieties adapted to your area which will however, such seed is the result of random pollina- reach maturity before an early frost. Many new tion by insects or other natural agents, and may not vegetable and flower varieties are hybrids, which produce plants typical of the parents. This is espe- cost a little more than open pollinated types. How- cially true of the many hybrid varieties. (See Veg- ever, hybrid plants usually have more vigor, more etables chapter for information on saving vegetable uniformity, and better production than nonhybrids seed.) Most seed companies take great care in and sometimes have specific disease resistance or handling seeds properly. Generally, do not expect other unique cultural characteristics. more than 65% to 80% of the seeds to germinate. From those germinating, expect about 60% to 75% to produce satisfactory, vigorous, sturdy seedlings.

Chapter 7 Plant Propagation 1 Germination has a minimum germination temperature of 50 degrees F. and a maximum temperature of 95 There are four environmental factors which affect degrees, but an optimum germination tempera- germination: water, oxygen, light, and heat. ture of about 80 degrees. Where germination temperatures are listed, they are usually the Water optimum temperatures unless otherwise speci- The first step in the germination process is the fied. Generally, 65 to 75 degrees F. is best for imbibition or absorption of water. Even though most plants. This often means the germination seeds have great absorbing power due to the flats may have to be placed in special chambers nature of the seed coat, the amount of available or on radiators, heating cables, or heating mats to water in the germination medium affects the maintain optimum temperature. The importance uptake of water. An adequate, continuous supply of maintaining proper medium temperature to of water is important to ensure germination. achieve maximum germination percentages Once the germination process has begun, a dry cannot be over-emphasized. period will cause the death of the embryo. Germination will begin when certain internal Light requirements have been met. A seed must have a Light is known to stimulate or to inhibit germi- mature embryo, contain a large enough endosperm nation of some seed. The light reaction involved to sustain the embryo during germination, and here is a complex process. Some crops which contain sufficient hormones or auxins to initiate the have a requirement for light to assist seed germi- process. nation are ageratum, begonia, browallia, impa- tiens, lettuce, and petunia. Conversely, calen- dula, centaurea, annual phlox, verbena, and vinca will germinate best in the dark. Other Methods of Breaking Dormancy plants are not specific at all. Seed catalogs and One of the functions of dormancy is to prevent a seed packets often list germination or cultural seed from germinating before it is surrounded by a tips for individual varieties. When sowing light- favorable environment. In some trees and shrubs, requiring seed, do as nature does, and leave seed dormancy is difficult to break, even when the them on the soil surface. If they are covered at environment is ideal. Various treatments are per- all, cover them lightly with fine peat moss or fine formed on the seed to break dormancy and begin vermiculite. These two materials, if not applied germination. too heavily, will permit some light to reach the seed and will not limit germination. When Seed Scarification starting seed in the home, supplemental light can Seed scarification involves breaking, scratching, be provided by fluorescent fixtures suspended 6 or softening the seed coat so that water can enter to 12 inches above the seeds for 16 hours a day. and begin the germination process. There are several methods of scarifying seeds. In acid Oxygen scarification, seeds are put in a glass container In all viable seed, respiration takes place. The and covered with concentrated sulfuric acid. The respiration in dormant seed is low, but some seeds are gently stirred and allowed to soak from oxygen is required. The respiration rate increases 10 minutes to several hours, depending on the during germination, therefore, the medium in hardness of the seed coat. When the seed coat has which the seeds are placed should be loose and become thin, the seeds can be removed, washed, well-aerated. If the oxygen supply during germi- and planted. Another scarification method is nation is limited or reduced, germination can be mechanical. Seeds are filed with a metal file, severely retarded or inhibited. rubbed with sandpaper, or cracked with a hammer to weaken the seed coat. Hot water Heat scarification involves putting the seed into hot A favorable temperature is another important water (170 to 212 degrees F). The seeds are requirement of germination. It not only affects allowed to soak in the water, as it cools, for 12 to the germination percentage but also the rate of 24 hours and then planted. A fourth method is germination. Some seeds will germinate over a one of warm, moist scarification. In this case, wide range of temperatures, whereas others seeds are stored in nonsterile, warm, damp require a narrow range. Many seeds have mini- containers where the seed coat will be broken mum, maximum, and optimum temperatures at down by decay over several months. which they germinate. For example, tomato seed

Chapter 7 Plant Propagation 2 Seed Stratification Starting Seeds Seeds of some fall-ripening trees and shrubs of Media the temperate zone will not germinate unless A wide range of materials can be used to start chilled underground as they over winter. This so seeds, from plain vermiculite or mixtures of called “after ripening” may be accomplished soilless media to the various amended soil mixes. artificially by a practice called stratification. The With experience, you will learn to determine following procedure is usually successful. Put what works best under your conditions. How- sand or vermiculite in a clay pot to about 1 inch ever, keep in mind what the good qualities of a from the top. Place the seeds on top of the me- germinating medium are. It should be rather fine dium and cover with ½ inch of sand or vermicu- and uniform, yet well-aerated and loose. It lite. Wet the medium thoroughly and allow should be free of insects, disease organisms, and excess water to drain through the hole in the pot. weed seeds. It should also be of low fertility or Place the pot containing the moist medium and total soluble salts and capable of holding and seeds in a plastic bag and seal. Place the bag in a moving moisture by capillary action. One mix- refrigerator. Periodically check to see that the ture which supplies these factors is a combina- medium is moist, but not wet. Additional water tion of 1/3 sterilized soil, 1/3 sand or vermiculite will probably not be necessary. After 10 to 12 or perlite, and 1/3 peat moss. weeks, remove the bag from the refrigerator. Take the pot out and set it in a warm place in the The importance of using a sterile medium and house. Water often enough to keep the medium container cannot be over-emphasized. The home moist. Soon the seedlings should emerge. When gardener can treat a small quantity of soil mix- the young plants are about 3 inches tall, trans- ture in an oven. Place the slightly moist soil in a plant them into pots to grow until time for heat-resistant container in an oven set at about setting outside. 250 degrees F. Use a candy or meat thermometer to ensure that the mix reaches a temperature of Another procedure that is usually successful uses 180 degrees F. for at least 1/2 hour. Avoid over- sphagnum moss or peat moss. Wet the moss heating as this can be extremely damaging to the thoroughly, then squeeze out the excess water soil. Be aware that the heat will release very with your hands. Mix seed with the sphagnum or unpleasant odors in the process of sterilization. peat and place in a plastic bag. Seal the bag and This treatment should prevent damping-off and put it in a refrigerator. Check periodically. If other plant diseases, as well as eliminate poten- there is condensation on the inside of the bag, the tial plant pests. Growing containers and imple- process will probably be successful. After 10 to ments should be washed to remove any debris, 12 weeks remove the bag from the refrigerator. then rinsed in a solution of 1 part chlorine bleach Plant the seeds in pots to germinate and grow. to 9 parts water. Handle seeds carefully. Often the small roots and shoots are emerging at the end of the stratifica- An artificial, soilless mix also provides the tion period. Care must be taken not to break desired qualities of a good germination medium. these off. Temperatures in the range of 35 to 45 The basic ingredients of such a mix are sphag- degrees F (2 to 70C) are effective. Most refrigera- num peat moss and vermiculite, both of which tors operate in this range. Seeds of most fruit and are generally free of diseases, weed seeds, and nut trees can be successfully germinated by these insects. The ingredients are also readily available, procedures. Seeds of peaches should be removed easy to handle, lightweight, and produce uni- from the hard pit. Care must be taken when form plant growth. “Peat-lite” mixes or similar cracking the pits. Any injury to the seed itself can products are commercially available or can be be an entry path for disease organisms. made at home using this recipe: 4 quarts of shredded sphagnum peat moss, 4 quarts of fine vermiculite, 1 tablespoon of superphosphate, and 2 tablespoons of ground limestone. Mix thor- oughly. These mixes have little fertility, so seedlings must be watered with a diluted fertil- izer solution soon after they emerge. Do not use garden soil by itself to start seedlings; it is not sterile, is too heavy, and will not drain well.

Chapter 7 Plant Propagation 3 Containers Seedlings in rows are easier to label and handle Flats and trays can be purchased or you can at transplanting time than those which have been make your own from scrap lumber. A convenient sown in a broadcast manner. Sow the seeds size to handle would be about 12 to 18 inches thinly and uniformly in the rows by gently long and 12 inches wide with a depth of about 2 tapping the packet of seed as it is moved along inches. Leave cracks of about 1/8-inch between the row. Lightly cover the seed with dry ver- the boards in the bottom or drill a series of holes miculite or sifted medium if they require dark- to ensure good drainage. ness for germination. A suitable planting depth is usually about twice the diameter of the seed. You can also make your own containers for starting seeds by recycling such things as cottage Do not plant seeds too deeply. Extremely fine cheese containers, the bottoms of milk cartons or seed such as petunia, begonia, and snapdragon bleach containers, and pie pans, as long as good are not covered, but lightly pressed into the drainage is provided. At least one company has medium or watered in with a fine mist. If these developed a form for recycling newspaper into seeds are broadcast, strive for a uniform stand by pots, and another has developed a method for sowing half the seeds in one direction, then the consumer to make and use compressed sowing the other way with the remaining seed in blocks of soil mix instead of pots. a crossing pattern.

Clay or plastic pots can be used and numerous Large seeds are frequently sown into some sort types of pots and strips made of compressed peat of a small container or cell pack which eliminates are also on the market. Plant bands and plastic the need for early transplanting. Usually 2 or 3 cell packs are also available. Each cell or mini-pot seeds are sown per unit and later thinned to holds a single plant which reduces the risk of allow the strongest seedling to grow. root injury when transplanting. Peat pellets, peat or fiber-based blocks, and expanded foam cubes Seed Tape can also be used for seeding. Most garden stores and seed catalogs offer indoor and outdoor seed tapes. Seed tape has Seeding precisely spaced seeds enclosed in an organic, The proper time for sowing seeds for transplants water-soluble material. When planted, the tape depends upon when plants may safely be moved dissolves and the seeds germinate normally. Seed out-of-doors in your area. This period may range tapes are especially convenient for tiny, hard-to- from 4 to 12 weeks prior to transplanting, de- handle seeds. However, tapes are much more pending upon the speed of germination, the rate expensive per seed. Seed tapes allow uniform of growth, and the cultural conditions provided. emergence, eliminate overcrowding, and permit A common mistake is to sow the seeds too early sowing in perfectly straight rows. The tapes can and then attempt to hold the seedlings back be cut at any point for multiple-row plantings, under poor light or improper temperature and thinning is rarely necessary. ranges. This usually results in tall, weak, spindly plants which do not perform well in the garden. Pregermination Another method of starting seeds is After selecting a container, fill it to within 3/4 pregermination. This method involves sprouting inch of the top with moistened growing medium. the seeds before they are planted in pots or in the For very small seeds, at least the top ¼-inch garden. This reduces the time to germination, as should be a fine, screened mix or a layer of the temperature and moisture are easy to control. vermiculite. Firm the medium at the corners and A high percentage of germination is achieved edges with your fingers or a block of wood to since environmental factors are optimum. Lay provide a uniform, flat surface. seeds between the folds of a cotton cloth or on a layer of vermiculite in a shallow pan. Keep moist, For medium and large seeds, make furrows 1 to 2 in a warm place. When roots begin to show, inches apart and 1/8 to ¼-inch deep across the place the seeds in containers or plant them surface of the container using a narrow board or directly in the garden. While transplanting pot label. By sowing in rows, good light and air seedlings, be careful not to break off tender roots. movement results, and if damping-off fungus Continued attention to watering is critical. does appear, there is less chance of it spreading.

Chapter 7 Plant Propagation 4 When planting seeds in a container that will be Lack of uniformity, overwatering, or drying out set out in the garden later, place 1 seed in a 2- to are problems related to manual watering. Excel- 3-inch container. Plant the seeds at only ½ the lent germination and moisture uniformity can be recommended depth. Gently press a little soil obtained with a low-pressure misting system. over the sprouted seed and then add about ¼ Four seconds of mist every 6 minutes or 10 inch of milled sphagnum or sand to the soil seconds every 15 minutes during the daytime in surface. These materials will keep the surface spring seems to be satisfactory. Bottom heat is an uniformly moist and are easy for the shoot to asset with a mist system. Subirrigation or water- push through. Keep in a warm place and care for ing from below may work well, keeping the flats them as for any other newly transplanted seed- moist. However, as the flats or pots must sit in lings. water constantly, the soil may absorb too much water, and the seeds may rot due to lack of A convenient way to plant small, delicate, oxygen. pregerminated seeds is to suspend them in a gel. You can make a gel by blending cornstarch with Temperature and Light boiling water to a consistency that is thick Several factors for good germination have al- enough so the seeds will stay suspended. Be sure ready been mentioned. The last item, and by no to cool thoroughly before use. Place the gel with means the least important, is temperature. Since seedlings in a plastic bag with a hole in it. most seeds will germinate best at an optimum Squeeze the gel through the hole along a temperature that is usually higher than most premarked garden row. Spacing of seeds is home night temperatures, special warm areas determined by the number of seeds in the gel. If must often be provided. The use of thermostati- the spacing is too dense, add more gel; if too cally controlled heating cables is an excellent wide, add more seeds. The gel will keep the method of providing constant heat. germinating seeds moist until they establish themselves in the garden soil. After germination and seedling establishment, move the flats to a light, airy, cooler location, at a Watering 55 to 60 degree F. night temperature and a 65 to After the seed has been sown, moisten the plant- 70 degree F. day reading. This will prevent soft, ing mix thoroughly. Use a fine mist or place the leggy growth and minimize disease troubles. containers in a pan or tray which contains about Some crops, of course, may germinate or grow 1 inch of warm water. Avoid splashing or exces- best at a different constant temperature and must sive flooding which might displace small seeds. be handled separately from the bulk of the When the planting mix is saturated, set the plants. container aside to drain. The soil should be moist but not wet. Seedlings must receive bright light after germina- tion. Place them in a window facing south, if Ideally, seed flats should remain sufficiently possible. If a large, bright window is not avail- moist during the germination period without able, place the seedlings under a fluorescent having to add water. One way to maintain light. Use two 40-watt, cool-white fluorescent moisture is to slip the whole flat or pot into a tubes or special plant growth lamps. Position the clear plastic bag after the initial watering. The plants 6 inches from the tubes and keep the lights plastic should be at least 1 inch from the soil. on about 16 hours each day. As the seedlings Keep the container out of direct sunlight, other- grow, the lights should be raised. wise the temperature may rise to the point where the seeds will be harmed. Many home gardeners cover their flats with panes of glass instead of using a plastic sleeve. Be sure to remove the plastic bag or glass cover as soon as the first seedlings appear. Surface watering can then be practiced if care and good judgement are used.

Chapter 7 Plant Propagation 5 Seed Requirements

PLANT APPROXIMATE APPROXIMATE GERMINATION GERMINATION TIME TO SEED GERMINATION TEMPERATURE IN LIGHT (L) BEFORE LAST TIME (degrees F.) OR DARK (D) SPRING FROST (days)

Begonia 12 weeks or 10 - 15 70 L Browallia more 15 - 20 70 L Geranium 10 - 20 70 L Larkspur 5 - 10 55 D Pansy (Viola) 5 - 10 65 D Vinca 10 - 15 70 D

Dianthus 10 weeks 5 - 10 70 - Impatiens 15 - 20 70 L Petunia 5 - 10 70 L Portulaca 5 - 10 70 D Snapdragon 5 - 10 65 L Stock 10 - 15 70 - Verbena 15 - 20 65 D

Ageratum 8 weeks 5 - 10 70 L Alyssum 5 - 10 70 - Broccoli 5 - 10 70 - Cabbage 5 - 10 70 - Cauliflower 5 - 10 70 - Celosia 5 - 10 70 - Coleus 5 - 10 65 L Dahlia 5 - 10 70 - Eggplant 5 - 10 70 - Head lettuce 5 - 10 70 L Nicotiana 10 - 15 70 L Pepper 5 - 10 80 - Phlox 5 - 10 65 D

Aster 6 weeks 5 - 10 70 - Balsam 5 - 10 70 - Centurea 5 - 10 65 D Marigold 5 - 10 70 - Tomato 5 - 10 80 - Zinnia 5 - 10 70 -

Cucumber 4 weeks 5 - 10 85 - Cosmos or less 5 - 10 70 - Muskmelon 5 - 10 85 - Squash 5 - 10 85 - Watermelon 5 - 10 85 -

Chapter 7 Plant Propagation 6 Transplanting and Handling Containers for Transplanting There is a wide variety of containers from which If the plants have not been seeded in individual to choose for transplanting seedlings. These containers, they must be transplanted to give containers should be economical, durable, and them proper growing space. One of the most make good use of space. The type selected will common mistakes made is leaving the seedlings depend on the type of plant to be transplanted in the seed flat too long. The ideal time to trans- and individual growing conditions. Standard plant young seedlings is when they are small and pots may be used, but they waste a great deal of there is little danger from setback. This is usually space and may not dry out rapidly enough for about the time the first true leaves appear above the seedling to have sufficient oxygen for proper or between the cotyledon leaves (the cotyledons development. or seed leaves are the first leaves the seedling produces). Don’t let plants get hard and stunted There are many types of containers available or tall and leggy. commercially. Those made out of pressed peat can be purchased in varying sizes. Individual Seedling growing mixes and containers can be pots or strips of connected pots fit closely to- purchased or prepared similar to those men- gether, are inexpensive, and can be planted tioned for germinating seed. The medium should directly in the garden. When setting out plants contain more plant nutrients than a germination grown in peat pots, be sure to cover the pot mix, however. Some commercial soilless mixes completely. If the top edge of the peat pot ex- have fertilizer already added. When fertilizing, tends above the soil level, it may act as a wick, use a soluble house plant fertilizer, at the dilu- and draw water away from the soil in the pot. To tion recommended by the manufacturer, about avoid this, tear off the top lip of the pot and then every 2 weeks after the seedlings are established. plant flush with the soil level. Remember that young seedlings are easily damaged by too much fertilizer, especially if they Community packs are containers in which there are under any moisture stress. is room to plant several plants. These are gener- ally inexpensive. The main disadvantage of a To transplant, carefully dig up the small plants community pack is that the roots of the indi- with a knife or wooden plant label. Let the group vidual plants must be broken or cut apart when of seedlings fall apart and pick out individual separating them to put out in the garden. plants. Gently ease them apart in small groups which will make it easier to separate individual Compressed peat pellets, when soaked in water, plants. Avoid tearing roots in the process. expand to form compact, individual pots. They Handle small seedlings by their leaves, not their waste no space, don’t fall apart as badly as peat delicate stems. Punch a hole in the medium into pots, and can be set directly out in the garden. If which the seedling will be planted. Make it deep you wish to avoid transplanting seedlings enough so the seedling can be put at the same altogether, compressed peat pellets are excellent depth it was growing in the seed flat. Small for direct sowing. plants or slow growers should be placed 1 inch apart and rapid-growing, large seedlings about 2 Community packs and cell packs, which are inches apart. After planting, firm the soil and strips of connected individual pots, are also water gently. Keep newly transplanted seedlings available in plastic and are frequently used by in the shade for a few days, or place them under commercial bedding plant growers, as they fluorescent lights. Keep them away from direct withstand frequent handling. In addition, many heat sources. Continue watering and fertilizing homeowners find a variety of materials from as in the seed flats. around the house useful for containers. These homemade containers should be deep enough to Most plants transplant well and can be started provide adequate soil and have plenty of drain- indoors, but a few plants are difficult to trans- age holes in the bottom. plant. These are generally directly seeded out- doors or sown directly into individual containers indoors. Examples include zinnias and cucurbits, such as melons and squash.

Chapter 7 Plant Propagation 7 Hardening Plants Propagation of Ferns by Spores Hardening is the process of altering the quality of Though ferns are more easily propagated by other plant growth to withstand the change in environ- methods, some gardeners like the challenge of mental conditions which occurs when plants are raising ferns from spores. One tested method for transferred from a greenhouse or home to the small quantities follows: garden. A severe check in growth may occur if plants produced in the home are planted out- Put a solid, sterilized brick (bake at 250 degrees F. doors without a transition period. Hardening is for 30 minutes) in a pan and add water to cover the most critical with early crops, when adverse brick. When the brick is wet throughout, squeeze a climatic conditions can be expected. thin layer of moist soil and peat (1:1) onto the top of the brick. Pack a second layer (about an inch) on top Hardening can be accomplished by gradually of that. Sprinkle spores on top. Cover with plastic lowering temperatures and relative humidity (not touching the spores) and put in a warm place in and reducing water. This procedure results in an indirect light. It may take up to a month or more for accumulation of carbohydrates and a thickening the spores to germinate. Keep moist at all times. A of cell walls. A change from a soft, succulent type prothallus (one generation of the fern) will develop of growth to a firmer, harder type is desired. first from each spore, forming a light green mat. Mist lightly once a week to maintain high surface This process should be started at least 2 weeks moisture; the sperm must be able to swim to the before planting in the garden. If possible, plants archegonia (female parts). After about three weeks, should be moved to a 45 to 50 degree F. tempera- fertilization should have occurred. Pull the mat ture indoors or outdoors in a shady location. A apart with tweezers in ¼-inch squares and space cold frame is excellent for this purpose. When them ½-inch apart in a flat containing a 2-inch layer put outdoors, plants should be shaded, then of sand, ¼-inch of charcoal, and about 2 inches of gradually moved into sunlight. Each day, gradu- soil/peat mix. Cover with plastic and keep moist. ally increase the length of exposure. Don’t put When fern fronds appear and become crowded, tender seedlings outdoors on windy days or transplant to small pots. Gradually reduce the when temperatures are below 45 degrees F. humidity until they can survive in the open. Light Reduce the frequency of watering to slow exposure may be increased at this time. growth, but don’t allow plants to wilt. Even cold- hardy plants will be hurt if exposed to freezing temperatures before they are hardened. After proper hardening, however, they can be planted outdoors and light frosts will not damage them.

The hardening process is intended to slow plant growth. If carried to the extreme of actually stopping plant growth, significant damage can be done to certain crops. For example, cauliflower will make thumb size heads and fail to develop further if hardened too severely. Cucumbers and melons will stop growth if hardened.

Chapter 7 Plant Propagation 8 Asexual Propagation Place stem and leaf cuttings in bright, indirect light. Root cuttings can be kept in the dark until new Asexual propagation, as mentioned earlier, is the shoots appear. best way to maintain some species, particularly an individual that best represents that species. Clones are groups of plants that are identical to their one Stem Cuttings parent and that can only be propagated asexually. Numerous plant species are propagated by stem The Bartlett pear (1770) and the Delicious apple cuttings. Some can be taken at any time of the (1870) are two examples of clones that have been year, but stem cuttings of many woody plants asexually propagated for many years. must be taken in the fall or in the dormant season. The major methods of asexual propagation are cuttings, layering, division, budding and grafting. Tip cuttings: Detach a 2 to 6-inch piece of stem, Cuttings involve rooting a severed piece of the including the terminal bud. Make parent plant; layering involves rooting a part of the the cut just below a node. Remove parent and then severing it; and budding and lower leaves that would touch or grafting is joining two plant parts from different be below the medium. Dip the varieties. stem in rooting hormone if de- sired. Gently tap the end of the cutting to remove excess hormone. Cuttings Insert the cutting deeply enough Many types of plants, both woody and herbaceous, into the media to support itself. At are frequently propagated by cuttings. A cutting is a least one node must be below the vegetative plant part which is severed from the surface. parent plant in order to regenerate itself, thereby Tip cuttings forming a whole new plant.

Take cuttings with a sharp blade to reduce injury to the parent plant. Dip the cutting tool in rubbing alcohol or a mixture of one part bleach : nine parts Medial cuttings water to prevent transmitting diseases from infected Medial cuttings: Make the first cut just above a plant parts to healthy ones. Remove flowers and node, and the second cut just flower buds from cuttings to allow the cutting to above a node 2 to 6 inches down use its energy and stored carbohydrates for root and the stem. Prepare and insert the shoot formation rather than fruit and seed produc- cutting as you would a tip cutting. tion. To hasten rooting, increase the number of Be sure to position right side up. roots, or to obtain uniform rooting (except on soft, Axial buds are always above fleshy stems), use a rooting hormone, preferably leaves. one containing a fungicide. Prevent possible con- tamination of the entire supply of rooting hormone Cane cuttings: Cut cane-like stems into sections by putting some in a separate container for dipping containing one or two eyes, or cuttings. nodes. Dust ends with fungicide or activated charcoal. Allow to dry Insert cuttings into a rooting medium such as coarse several hours. Lay horizontally sand, vermiculite, soil, water, or a mixture of peat with about half of the cutting and perlite. It is important to choose the correct below the media surface, eye rooting medium to get optimum rooting in the facing upward. Cane cuttings are shortest time. In general, the rooting medium usually potted when roots and should be sterile, low in fertility, drain well enough new shoots appear but new shoots to provide oxygen, and retain enough moisture to from dracaena and croton are often prevent water stress. Moisten the medium before cut off and re-rooted in sand. inserting cuttings, and keep it evenly moist while cuttings are rooting and forming new shoots.

Chapter 7 Plant Propagation 9 Single Eye: The eye refers to the node. This is Split vein: Detach a leaf from the stock plant. used for plants with alternate Slit its veins on the lower leaf leaves when space or stock mate- surface. Lay the cutting, lower side rial are limited. Cut the stem about down, on the medium. New plants ½-inch above and ½-inch below a will form at each cut. If the leaf node. Place cutting horizontally or tends to curl up, hold it in place by vertically in the medium. covering the margins with the rooting medium. Double Eye: This is used for plants with oppo- site leaves when space or stock material is limited. Cut the stem Leaf sections: This method is frequently used about 12-inches above and 12- with snake plant and fibrous inches below the same node. Insert rooted begonias. Cut begonia the cutting vertically in the me- leaves into wedges with at least dium with the node just touching one vein. Lay leaves flat on the the surface. medium. A new plant will arise at the vein. Cut snake plant leaves Heel cutting: This method uses stock material into 2-inch sections. Consistently with woody stems efficiently. make the lower cut slanted and the Make a shield-shaped cut about upper cut straight so you can tell halfway through the wood around which is the top. Insert the cutting a leaf and axial bud. Insert the vertically. Roots will form fairly shield horizontally into the me- soon, and eventually a new plant dium. will appear at the base of the cutting. These and other succulent cuttings will rot if kept too moist. Leaf Cuttings Leaf cuttings are used almost exclusively for a few indoor plants. Leaves of most plants will Root Cuttings either produce a few roots but no plant, or just Root cuttings are usually taken from 2 to 3 year decay. old plants during their dormant season when they have a large carbohydrate supply. Root Whole leaf cuttings of some species produce new shoots, with petiole: Detach the leaf and up to 1½ which then form their own root systems, while inches of petiole. Insert the lower root cuttings of other plants develop root sys- end of the petiole into the medium. tems before producing new shoots. One or more new plants will form at the base of the petiole. The leaf Plants with may be severed from the new large roots: Make a straight top cut. Make a plants when they have their own slanted cut 2 to 6 inches below the roots, and the petiole reused. first cut. Store about 3 weeks in moist sawdust, peat moss, or sand at 40 degrees F. Remove from Whole leaf storage. Insert the cutting verti- without petiole: This is used for plants with sessile cally with the top approximately leaves. Insert the cutting vertically level with the surface of the into the medium. A new plant will rooting medium. This method is form from the axillary bud. The often used outdoors. leaf may be removed when the new plant has its own roots.

Chapter 7 Plant Propagation 10 Plants with Compound small roots: Take 1 to 2 inch sections of roots. layering: This method works for plants with Insert the cuttings horizontally flexible stems. Bend the stem to the about 12 inch below the medium rooting medium surface. This method is usually as for simple used indoors or in a hotbed. layering, but alternately cover and expose stem sections. Wound Layering the lower side of the stem sections Stems still attached to their parent plants may form to be covered. Examples: heart-leaf roots where they touch a rooting medium. Severed philodendron, pothos. from the parent plant, the rooted stem becomes a new plant. This method of vegetative propagation, called layering, promotes a high success rate be- Mound (stool) cause it prevents the water stress and carbohydrate layering: Cut the plant back to 1 inch above shortage that plague cuttings. the ground in the dormant season. Mound soil over the emerging Some plants layer themselves naturally, but some- shoots in the spring to enhance times plant propagators assist the process. Layering their rooting. Examples: gooseber- is enhanced by wounding one side of the stem or by ries, apple rootstocks. bending it very sharply. The rooting medium should always provide aeration and a constant supply of moisture. Air layering: Air layering is used Tip layering: Dig a hole 3 to 4 inches deep. to propagate some indoor plants Insert the shoot tip and cover it with thick stems, or to rejuvenate with soil. The tip grows down- them when they become leggy. Slit ward first, then bends the stem just below a node. Pry the sharply and grows upward. slit open with a toothpick. Sur- Roots form at the bend, and round the wound with wet the recurved tip becomes a unmilled sphagnum moss. Wrap new plant. Remove the tip plastic or foil around the sphag- layer and plant it in the early num moss and tie in place. When spring or late fall. Examples: roots pervade the moss, cut the purple and black raspberries, plant off below the root ball. trailing blackberries. Examples: dumbcane, rubber tree. The following propagation methods can all be Simple layering: Bend the stem to the ground. Cover part of it with soil, leaving the last 6 to 12 inches exposed. Bend the tip into a vertical position and stake in place. The sharp bend will often induce rooting, but wound- ing the lower side of the branch or loosening the bark by twisting the stem may help. Examples: rhododen- dron, honeysuckle.

Chapter 7 Plant Propagation 11 considered types of layering, as the new plants form Corms: A large new corm forms on top of before they are detached from their parent plants. the old corm, and tiny cormels form around the large corm. After Stolons and Separation the leaves wither, dig up the runners: A stolon is a horizontal, often Corms corms and allow them to dry fleshy stem that can root, then in indirect light for 2 or 3 produce new shoots where it weeks. Remove the cormels, touches the medium. A runner is a then gently separate the new slender stem that originates in a corm from the old corm. Dust leaf axil and grows all new corms with a fungicide along the ground or and store in a cool place until downward from a planting time. Examples: hanging basket, crocus, gladiolus. producing a new plant at its tip. Plants that produce stolons or Division runners are propagated by sever- Plants with more than one rooted crown may be ing the new plants from their divided and the crowns planted separately. If the parent stems. Plantlets at the tips stems are not joined, gently pull the plants apart. If of runners may be rooted while the crowns are united by horizontal stems, cut the still attached to the parent, or stems and roots with a sharp knife to minimize detached and placed in a rooting injury. Divisions of some outdoor plants should be medium. Examples: strawberry, dusted with a fungicide before they are replanted. spider plant. Examples: snake plant, iris, prayer plant, day lilies. Offsets: Plants with a rosetted stem often reproduce by forming new shoots at their base or in leaf axils. Sever the new shoots from the parent plant after they have developed their own root system. Unrooted offsets of some species may be removed and placed in a rooting medium. Some of these must be cut off, while others may be simply Grafting lifted off of the parent stem. Grafting and budding are methods of asexual plant Examples: date palm, haworthia, propagation that join plant parts so they will grow bromeliads, many cacti. as one plant. These techniques are used to propa- gate cultivars that will not root well as cuttings or Separation: Separation is a term applied to a whose own root systems are inadequate. One or form of propagation by which more new cultivars can be added to existing fruit plants that produce bulbs or corms and nut trees by grafting or budding. multiply. The portion of the cultivar that is to be propagated Bulbs: New bulbs form beside the origi- is called the scion. It consists of a piece of shoot with nally planted bulb. Separate these dormant buds that will produce the stem and bulb clumps every 3 to 5 years for branches. The rootstock, or stock, provides the new largest blooms and to increase plant’s root system and sometimes the lower part of bulb population. Dig up the clump the stem. The cambium is a layer of cells located after the leaves have withered. between the wood and bark of a stem from which Gently pull the bulbs apart and new bark and wood cells originate. (See Fruit replant them immediately so their chapter for discussion of apple rootstock). roots can begin to develop. Small, new bulbs may not flower for 2 or Four conditions must be met for grafting to be 3 years, but large ones should successful: the scion and rootstock must be compat- bloom the first year. Examples: ible; each must be at the proper physiological stage; tulip, narcissus. Chapter 7 Plant Propagation 12 the cambial layers of the scion and stock must meet; Whip or tongue and the graft union must be kept moist until the grafting: This method is often used for wound has healed. material 1/4 to ½ inch in diameter. The scion and rootstock are usu- Cleft grafting: Cleft grafting is often used to ally of the same diameter, but the change the cultivar or top growth scion may be narrower than the of a shoot or a young tree (usually stock. This strong graft heals a seedling). It is especially success- quickly and provides excellent ful if done in the early spring. cambial contact. Make one 2½-inch Collect scion wood 3/8 to 5/8 inch long sloping cut at the top of the in diameter. Cut the limb or small rootstock and a matching cut on tree trunk to be reworked, perpen- the bottom of the scion. On the cut dicular to its length. Make a 2-inch surface, slice downward into the vertical cut through the center of stock and up into the scion so the the previous cut. Be careful not to pieces will interlock. Fit the pieces tear the bark. Keep this cut together, then tie and wax the wedged apart. Cut the lower end union. of each scion piece into a wedge. Prepare two scion pieces 3 to 4 inches long. Insert the scions at the Care of the Graft: Very little success in grafting will outer edges of the cut in the stock. be obtained unless proper care is maintained for the Tilt the top of the scion slightly following year or two. If a binding material such as outward and the bottom slightly strong cord or nursery tape is used on the graft, this inward to be sure the cambial must be cut shortly after growth starts to prevent layers of the scion and stock touch. girdling. Rubber budding strips have some advan- Remove the wedge propping the tages over other materials. They expand with slit open and cover all cut surfaces growth and usually do not need to be cut, as they with grafting wax. deteriorate and break after a short time. It is also an excellent idea to inspect the grafts after 2 or 3 weeks to see if the wax has cracked, and if necessary, Bark grafting: Unlike most grafting methods, rewax the exposed areas. After this, the union will bark grafting can be used on large probably be strong enough and no more waxing limbs, although these are often will be necessary. infected before the wound can completely heal. Collect scion Limbs of the old variety which are not selected for wood 3/8 to 1/2 inch in diameter grafting should be cut back at the time of grafting. when the plant is dormant, and The total leaf surface of the old variety should be store the wood wrapped in moist gradually reduced as the new one increases until at paper in a plastic bag in the refrig- the end of 1 or 2 years, the new variety has com- erator. Saw off the limb or trunk of pletely taken over. Completely removing all the the rootstock at a right angle to limbs of the old variety at the time of grafting itself. In the spring, when the bark increases the shock to the tree and causes excessive is easy to separate from the wood, suckering. Also, the scions may grow too fast, make a 12-inch diagonal cut on making them susceptible to wind damage. one side of the scion, and a 1½- inch diagonal cut on the other side. Leave two buds above the longer cut. Cut through the bark of the stock, a little wider than the scion. Remove the top third of the bark from this cut. Insert the scion with the longer cut against the wood. Nail the graft in place with flat- headed wire nails. Cover all wounds with grafting wax.

Chapter 7 Plant Propagation 13 Budding Care of Buds Place the bud in the stock in August. Force the Budding, or bud grafting, is the union of one bud bud to develop the following spring by cutting and a small piece of bark from the scion with a the stock off 3 to 4 inches above the bud. The new rootstock. It is especially useful when scion material shoot may be tied to the resulting stub to prevent is limited. It is also faster and forms a stronger damage from the wind. After the shoot has made union than grafting. a strong union with the stock, cut the stub off close to the budded area. Patch budding: Plants with thick bark should be patch budded. This is done while the plants are actively growing, so their bark slips easily. Remove a Plant Tissue Culture for the Home rectangular piece of bark from the Although technical procedures for aseptic culture of rootstock. Cover this wound with plant cells, tissues, and organs are as diverse as the a bud and matching piece of bark plant material on which they are practiced, a simpli- from the scion. If the rootstock’s fied general procedure can be followed in the home. bark is thicker than that of the All that is needed are a few basic supplies which scion, pare it down to meet the can easily be obtained. The procedures outlined in thinner bark so that when the this section can be used in the home to propagate union is wrapped the patch will be various species of plants, both easy (African violets, held firmly in place. coleus, chrysanthemums) and difficult (orchids, ferns, weeping figs) to propagate.

Chip budding: This budding method can be used when the bark is not slipping. Slice Medium Preparation downward into the rootstock at a For 2 pints of tissue culture medium, mix the follow- 45 degree angle through 1/4 ing ingredients in a 1-quart home canning jar: of the wood. Make a second cut upward from the first cut, 1/8 cup sugar about one inch. Remove a bud and attending chip of 1 teaspoon all-purpose, soluble fertilizer bark and wood from the mixture. Check the label to make sure it has scion shaped so that it fits the all of the major and minor elements, especially rootstock wound. Fit the bud ammonium nitrate. If the latter is lacking, add chip to the stock and wrap 1/3 tsp. of a 35-0-0 soluble fertilizer. the union. 1 tablet (100 mg) of inositol (myo-inositol) which can be obtained at most health food stores T-budding: This is the most commonly used budding technique. When the bark 1/4 of a pulverized vitamin tablet which has 1 is slipping, make a vertical cut to 2 mg of thiamine (same axis as the root stock) 4 Tablespoons coconut milk (cytokinin source) through the bark of the rootstock, drained from a fresh coconut. The remainder avoiding any buds on the can be frozen and used later. stock. Make a horizontal cut at the top of the vertical cut 3 to 4 grains (1/400 teaspoon!) of a (in a T shape) and loosen the commercial rooting compound which has 0.1 bark by twisting the knife at active ingredient IBA the intersection. Remove a • Fill the jar with distilled or deionized water. If shield-shaped piece of the purified water is not available, water that has scion, including a bud, bark, been boiled for several minutes can be and a thin section of wood. substituted. Push the shield under the loosened stock bark. Wrap the union, • Shake the mixture and make sure all materials leaving the bud exposed. have dissolved.

Chapter 7 Plant Propagation 14 • Baby food jars with lids, or other heat- solution. After this time period, rinse off excess resistant glass receptacles with lids can be bleach by dropping the plant part into sterile water. used as individual culture jars. They should Remember, once the plant material has been in the be half filled with cotton or paper to support bleach, it has been disinfested and should only be the plant material. The medium should be touched with sterile tweezers. poured into each culture bottle to the point where the support material is just above the After the plant material has been rinsed, remove solution. any bleach-damaged tissue with a sterile razor blade. Then remove the cap of a culture bottle When all bottles contain the medium and have the containing sterile medium, place the plant part onto lids loosely screwed on, they are ready to be steril- the support material in the bottle making sure that ized. This can be done by placing them in a pressure it is not completely submerged in the medium, and cooker and sterilizing them under pressure for 30 recap quickly. minutes or placing them in an oven at 320 degrees F. for 4 hours. After removing them from the Transferring should be done as quickly as possible sterilizer, place them in a clean area and allow the in a clean environment. Therefore, scrub hands and medium to cool. If the bottles will not be used for counter tops with soap and water just before begin- several days, wrap groups of culture bottles in foil ning to disinfest plant material. Rubbing alcohol or before sterilizing and then sterilize the whole a dilute bleach solution can be used to wipe down package. Then the bottles can be removed and the working surface. cooled without removing the foil cover. Sterilized water, tweezers, and razor blades, which will be After all plants have been cultured, place them in a needed later, can be prepared in the same manner. warm, well-lit (no direct sunlight) environment to encourage growth. If contamination of the medium has occurred, it should be obvious within 3 to 4 Plant Disinfestation and Culture days. Remove and wash contaminated culture Once the growing medium is sterilized and cooled, bottles as quickly as possible to prevent the spread plant material can be prepared for culture. Because to uncontaminated cultures. plants usually harbor bacterial and fungal spores, they must be cleaned (disinfested) before placement When plantlets have grown to sufficient size, on the sterile medium. Otherwise, bacteria and transplant them into soil. Handle as gently as fungi may grow faster than the plants and dominate possible because the plants are leaving a warm, the culture. humid environment for a cool, dry one. After transplanting, water the plants thoroughly and Various plant parts can be cultured, but small, place them in a clear plastic bag for several days. actively growing portions usually result in the most Gradually remove the bag to acclimate the plants to vigorous plantlets. For example, ferns are most their new environment; start with one hour per day readily propagated by using only ½ inch of the tip and gradually increase time out of the bag over a of a rhizome. For other species, ½ to 1 inch of the two-week period until the plants are strong enough shoot tip is sufficient. Remove leaves attached to the to dispense with the bag altogether. tip and discard. Place the plant part into a solution of 1 part commercial bleach to 9 parts water for 8 to 10 minutes. Submerge all plant tissue in the bleach

Chapter 7 Plant Propagation 15