Plant Propagation PDF

HO-98 Plant Propagation Adapted from the Virginia Master Gardener Handbook. Edited by Ray McNeilan, Extension agent emeritus, Multnomah County, Oregon State University. Edited for Kentucky by Richard Durham, consumer horticulture Extension specialist and state Master Gardener coordinator, Universit...

HO-98 Plant Propagation Adapted from the Virginia Master Gardener Handbook. Edited by Ray McNeilan, Extension agent emeritus, Multnomah County, Oregon State University. Edited for Kentucky by Richard Durham, consumer horticulture Extension specialist and state Master Gardener coordinator, University of Kentucky. (See Chapter 20, Vegetable Gardening, for information on In this chapter: saving vegetable seed.) Most seed companies take great care in handling seeds properly. Generally, do not expect more than Sexual Propagation  01 65 percent to 80 percent of the seeds to germinate. From those germinating, expect about 60 percent to 75 percent to produce Propagation of Ferns by Spores 06 satisfactory, vigorous, sturdy seedlings. Asexual Propagation 07 Germination There are four environmental factors that affect germination: Sexual Propagation water, oxygen, light, and heat. S exual propagation involves the union of the pollen (male) Water with the egg (female) to produce a seed. The seed is made The first step in the germination process is imbibition, or up of three parts: the outer seed coat, which protects the absorption of water. Even though seeds have great absorbent seed; the endosperm, which is a food reserve; and the embryo, power due to the nature of the seed coat, the amount of avail- which is the young plant itself. When a seed is mature and put able water in the germination medium affects the uptake of in a favorable environment, it will germinate, or begin active water. An adequate, continuous supply of water is important to growth. In this section, seed germination and transplanting of ensure germination. Once germination has begun, a dry period seeds are discussed. will cause death of the embryo. Seed Light To obtain quality plants, start with good quality seed from a Light is known to stimulate or to inhibit germination of some reliable dealer. Select varieties that will provide the size, color, seed. The light reaction involved here is a complex process. and habit of growth desired. Choose varieties adapted to your Examples of crops that need light to assist seed germination are area that will reach maturity before an early frost. Many new ageratum, begonia, browallia, impatiens, lettuce, and petunia. vegetable and flower varieties are hybrids, which cost a little Conversely, calendula, centaurea, annual phlox, verbena, and vinca more than open pollinated types. However, hybrid plants usu- will germinate best in the dark. Other plants are not specific at all. ally have more vigor and uniformity and better production than Seed catalogs and seed packets often list germination or cultural nonhybrids and sometimes have specific disease resistance or tips for individual varieties. When sowing light-requiring seed, other unique cultural characteristics. do as nature does, and leave them on the soil surface. If they are Although some seeds will keep for several years if stored to be covered at all, cover them lightly with fine peat moss or fine properly, it is advisable to purchase only enough seed for the vermiculite. These two materials, if not applied too heavily, will current year’s use. Good seed will not contain seed of any other permit some light to reach the seed and will not limit germina- crop or debris. Printing on the seed packet usually indicates tion. When starting seed in the home, supplemental light can be essential information about the variety, the year for which the provided by fluorescent fixtures suspended 6 to 12 inches above seeds were packaged, germination percentage you may typically the seeds for 16 hours a day. expect, and notes of any chemical seed treatment. If seeds are obtained well in advance of the actual sowing date or are stored Oxygen surplus seeds, keep them in a cool, dry place. Laminated foil In all viable seed, respiration takes place. Respiration in dor- packets help ensure dry storage. Paper packets are best kept mant seed is low, but some oxygen is required. The respiration in tightly closed containers and maintained around 40°F in rate increases during germination; therefore, the medium in low humidity. which the seeds are placed should be loose and well aerated. Some gardeners save seed from their own gardens; however, If the oxygen supply during germination is limited or reduced, such seed is the result of random pollination by insects or germination can be severely retarded or inhibited. other natural agents and may not produce plants typical of the parents, which is especially true of the many hybrid varieties. CHAPTER 03 Plant Propagation Heat Seed Stratification A favorable temperature is another important require- Seeds of some fall-ripening trees and shrubs of the temper- ment of germination. It affects the rate of germination as well ate zone will not germinate unless chilled underground as they as germination percentage. Some seeds will germinate over overwinter. This so-called “afterripening” can be accomplished a wide range of temperatures, while others require a narrow artificially by a practice called “stratification.” range. Many seed have minimum, maximum, and optimum The following stratification procedure is usually successful. temperatures at which they germinate. For example, tomato Put sand or vermiculite in a clay pot to about one inch from seed has a minimum germination temperature of 50°F and a the top. Place the seeds on top of the medium and cover with maximum temperature of 95°F but an optimum germination one-half inch of sand or vermiculite. Wet the medium thor- temperature of about 80°F. When germination temperatures are oughly and allow excess water to drain through the hole in the listed, usually the optimum temperatures are given unless oth- pot. Place the pot containing the moist medium and seeds in a erwise specified. Generally, 65° to 75°F is best for most plants. plastic bag and seal. Place the bag in a refrigerator. Periodically This range means germination flats often have to be placed in check to see that the medium is moist but not wet. Additional special chambers or on radiators, heating cables, or heating water will probably not be necessary. After 10 to 12 weeks, mats to maintain optimum temperature. The importance of remove the bag from the refrigerator, take the pot out and set maintaining proper medium temperature to achieve maximum it in a warm place in the house, and water often enough to keep germination percentages cannot be overemphasized. the medium moist. Soon the seedlings should emerge. When Germination will begin when certain internal requirements the young plants are about three inches tall, transplant them have been met. A seed must have a mature embryo, contain an into pots to grow until time for setting outside. endosperm large enough to sustain the embryo during germina- Another procedure that is usually successful uses sphagnum tion, and contain sufficient hormones to initiate the process. moss or peat moss. Wet the moss thoroughly, then squeeze out excess water with your hands. Mix seed with the sphagnum Methods of Breaking Dormancy or peat and place in a plastic bag. Seal the bag and put it in a refrigerator. Check it periodically. If there is condensation on One of the functions of dormancy is to prevent a seed from the inside of the bag, the process will probably be successful. germinating before it is surrounded by a favorable environ- After 10 to 12 weeks, remove the bag from the refrigerator and ment. In some trees and shrubs, seed dormancy is difficult plant the seeds in pots to germinate and grow. Handle seeds to break, even when the environment is ideal. The seed can carefully, because often the small roots and shoots are emerging be treated in various ways to break dormancy and cause it to at the end of the stratification period and care must be taken begin germinating. not to break these off. Temperatures in the range of 35° to 45°F Seed Scarification (2° to 7°C) are effective, and most refrigerators operate in this range. Seeds of most fruit and nut trees can be successfully Seed scarification involves breaking, scratching, or softening germinated by these procedures. Seeds of peaches should be the seed coat so that water can enter and begin the germina- removed from the hard pit. Care must be taken when cracking tion process. There are several methods of scarifying seeds. pits, because any injury to the seed itself can be an entry path In acid scarification, seeds are put in a glass container and for disease organisms. covered with concentrated sulfuric acid. The seeds are gently stirred and allowed to soak from 10 minutes to several hours, depending on the hardness of the seed coat. When the seed Starting Seeds coat has become thin, seeds can be removed, washed, and Media planted. Another scarification method is mechanical. Seeds A wide range of materials can be used to start seeds, from are filed with a metal file, rubbed with sandpaper, or cracked plain vermiculite or mixtures of soilless media to various with a hammer to weaken the seed coat. Hot water scarifica- amended soil mixes. With experience, you will learn what tion involves putting the seed into water that is 170° to 212°F. works best under your conditions. However, keep in mind The seeds are allowed to soak in the water as it cools for 12 to that germinating medium should be rather fine and uniform, 24 hours and then planted. A fourth method is one of warm, but also well aerated and loose. It also should be free of insects, moist scarification. In this case, seeds are stored in nonsterile, disease organisms, and weed seeds; of low fertility (indicated warm, damp containers, where the seed coat will be broken by low total soluble salts); and capable of holding and moving down by decay over several months. moisture by capillary action. The importance of using a sterile medium and container cannot be overemphasized (Figure 3.1). The home gardener can treat a small quantity of soil mixture in an oven to make it sterile. Place slightly moist soil in a heat-resistant container in an oven set at about 250°F. Use a candy or meat thermometer 3-2  Plant Propagation CHAPTER 03 “Peatlite” mixes or similar products are commercially avail- ºF / ºC able or can be made at home using this recipe: four quarts of 212 / 100 few resistant weed shredded sphagnum peat moss, four quarts of fine vermiculite, seeds; resistant plant one tablespoon of superphosphate, and two tablespoons of viruses ground limestone. (Superphosphate and ground limestone are 200 / 93 generally readily available from most garden centers or farm supply stores and can be found in the fertilizer section.)Mix thoroughly. These mixes have little fertility, so seedlings must 190 / 88 be watered with a diluted fertilizer 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. 180 / 82 Containers Flats and trays can be purchased, or you can make your own most weed seeds all plant 170 / 77 from scrap lumber. A convenient size would be 12 to 18 inches pathogenic long, 12 inches wide, and two inches deep. To ensure good bacteria; most plant drainage, leave an opening about one-eight inch wide between viruses 160 / 71 boards in the bottom of the tray or drill a series of holes where two board meet. most plant You can also make your own containers for starting seeds by pathogenic soil insects 150 / 66 recycling cottage cheese containers, bottoms of milk cartons, fungi bleach bottles, metal pie pans, etc., as long as good drainage most plant is provided. At least one company has developed a form for pathogenic 140 / 60 recycling newspaper to make pots, and another has developed bacteria; worms, slugs, centipedes botryis gray mold a method for the consumer to make and use compressed blocks of soil mix instead of pots. Clay or plastic pots also can be used. gladiolus 130 / 54 rhizoctonia solani Numerous types of pots and strips made of compressed peat yellows, are on the market. Plant bands and plastic cell packs, which fusarium are strips of connected individual pots, are also available. With 120 / 49 sclerotium rolfsii, these types of containers, each cell or minipot holds a single nematodes sclerotinia sclerotiorum plant, which reduces the risk of root injury when transplanting. water molds Peat pellets, peat or fiber-based blocks, and expanded foam 110 / 43 cubes can also be used for seeding. Seeding 100 / 38 The proper time for sowing seeds for transplants depends upon when plants may safely be moved outdoors in your area. Figure 3.1. Temperatures at which soil organisms are killed. This period can be from four to 12 weeks prior to transplant- ing, depending upon speed of germination, rate of growth, to ensure that the mix reaches a temperature of 140°F (or up and cultural conditions such as temperature and amount of to 180°F to control weed seeds) for at least 30 minutes. Avoid sunlight (Table 3.1). A common mistake is to sow seeds too overheating, as it can be extremely damaging to the soil. Be early and then attempt to hold the seedlings back under poor aware that the heat will release unpleasant odors during the light or improper temperature ranges, which usually results in sterilization process. This treatment should prevent damping- tall, weak, spindly plants that do not perform well in the garden. off and other plant diseases as well as eliminate potential plant pests. Growing containers and implements should be washed to Steps for seeding (see Figure 3.2): remove any debris then rinsed in a solution of one part chlorine After selecting a container, fill it with moistened growing bleach to 10 parts water. medium to within three-quarters of an inch of the top. For An artificial, soilless mix can also provide a good germina- very small seeds, at least the top one-quarter inch should be a tion medium and produce uniform plant growth. The basic fine, screened mix or a layer of vermiculite. Firm the medium ingredients of such a mix are sphagnum peat moss and ver- at the corners and edges with your fingers or a block of wood miculite, both of which are readily available, easy to handle, to provide a uniform, flat surface. and lightweight. One mixture that has these characteristics For medium and large seeds, make furrows one to two inches is a combination of one-third sterilized soil, one-third sand apart and one-eighth to one-quarter inch deep across the surface or vermiculite or perlite, and one-third sphagnum peat moss. of the container using a narrow board, pointed end of a plastic 3-3 CHAPTER 03 Plant Propagation Table 3.1. Seed Requirements. Step 1. Make shallow depressions Approx. Approx. Germ. in the medium for Germ. in Time to Seed Germ. Temp. uniform seeding. Plant Light (L) or before Last Time (Degrees Dark (D) Spring Frost* (days) F) 12 weeks or Begonia 10 - 15 70 L more Browallia 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 10 weeks Dianthus 5 - 10 70 -- Step 2. Sow the Impatiens 15 - 20 70 L seeds thinly and Petunia 5 - 10 70 L evenly. Label each variety. Portulaca 5 - 10 70 D Snapdragon 5 - 10 65 L Stock 10 - 15 70 -- Verbena 15 - 20 65 D 8 weeks Ageratum 5 - 10 70 L Alyssum 5 - 10 70 -- Broccoli 5 - 10 70 -- Cabbage 5 - 10 70 -- Cauliflower 5 - 10 70 -- Celosia 5 - 10 70 -- Step 3. Cover the seeds with dry Coleus 5 - 10 65 L vermiculite. Water carefully. Dahlia 5 - 10 70 -- Eggplant 5 - 10 70 -- vermiculite Head lettuce 5 - 10 70 L soil mixture Nicotiana 10 - 15 70 L Pepper 5 - 10 80 -- Phlox 5 - 10 65 D Figure 3.2. Sowing seeds in a starter flat. 6 weeks Aster 5 - 10 70 -- Balsam 5 - 10 70 -- Do not plant seeds too deeply. A suitable planting depth is Centurea 5 - 10 65 D usually about twice the diameter of the seed. Extremely fine Marigold 5 - 10 70 -- seed such as petunia, begonia, and snapdragon are not covered; Tomato 5 - 10 80 -- they are lightly pressed into the medium or watered in with a Zinnia 5 - 10 70 -- fine mist. If fine seeds are broadcast, strive for a uniform stand 4 weeks or less Cucumber 5 - 10 85 -- by sowing half the seeds in one direction, then sowing the Cosmos 5 - 10 70 -- remaining seed in the opposite crosswise direction. Muskmelon 5 - 10 85 -- Large seeds are frequently sown into some sort of small con- Squash 5 - 10 85 -- tainer or cell pack, eliminating the need for early transplanting. Watermelon 5 - 10 85 -- To allow the strongest seedling to grow, two or three large seeds *Length of time is based on relative rate of seeding growth and how long it usually are sown per unit and later thinned. will take to obtain a sizeable transplant. Seed Tape pot label, or even the dull point of a pencil. Sowing in rows pro- Most garden stores and seed catalogs offer indoor and out- duces good exposure to light and air movement, and if damp- door seed in tape. Seed tape, although much more expensive ingoff fungus appears, there is less chance of it spreading. Also, per seed, has precisely spaced seeds enclosed in an organic, seedlings in rows are easier to label and handle at transplanting water-soluble material. When planted, the tape dissolves and time than those that have been sown in a broadcast manner. Sow seeds germinate normally. Seed tapes are especially convenient seeds thinly and uniformly in rows by gently tapping the packet for tiny, hard-to-handle seeds. They allow uniform emergence, of seed as you move it along the row. If seeds require darkness eliminate overcrowding, and permit sowing in perfectly straight for germination, lightly cover them with dry vermiculite or rows. Tapes can be cut at any point for multiple-row plantings, sifted medium. and thinning is rarely necessary. 3-4  Plant Propagation CHAPTER 03 Pregermination constantly, the soil may absorb too much water, and the seeds Another method of starting seeds is pregermination, which may rot due to lack of oxygen. involves sprouting seeds before they are planted in pots or Temperature and Light in the garden. This method reduces time to germination, as temperature and moisture are easy to control. A high percent- Since most seeds will germinate best at an optimum tem- age of germination is achieved, since environmental factors perature that is usually higher than most home night tem- are optimum. To pregerminate seeds, lay them between folds peratures, special warm areas often must be provided. The use of a cotton cloth or on a layer of vermiculite in a shallow pan. of thermostatically controlled heating cables is an excellent Keep seed in a warm place, and, because continued attention to method of providing constant heat. watering is critical, keep the cloth or vermiculite moist. When After germination and seedling establishment, move flats to roots begin to show, place seeds in containers or plant them a light, airy, cooler location at a 55° to 60°F night temperature directly in the garden. While transplanting pregerminated and a 65° to 70°F day reading, which will prevent soft, leggy seedlings, be careful not to break off tender roots. growth and minimize disease troubles. Some crops, of course, When planting pregerminated seeds in containers that will may germinate or grow best at a different constant temperature be set out in the garden later, use containers that are two to and must be handled separately from the bulk of the plants. three inches in diameter, with one seed per container. Plant the Seedlings must receive bright light after germination. Place seeds at only half the recommended depth. Gently press a little them in a window facing south, if possible. If a large, bright soil over the sprouted seed and then add about one-quarter window is not available, place seedlings under a fluorescent inch of milled sphagnum or sand to the soil surface, which will light. Use two 40-watt, cool-white fluorescent tubes or special keep the surface uniformly moist and enable the shoot to push plant growth lamps. Position plants six inches from the tubes through easily. Keep these containers in a warm place and care and keep lights on about 16 hours each day. As seedlings grow, for the seedlings as for any other newly transplanted seedlings. lights should be raised. Watering Transplanting and Handling After the seed has been sown, thoroughly moisten the plant- If plants have not been seeded in individual containers, they ing mix. Use a fine mist or place the containers in a pan or tray must be transplanted to give them proper growing space. One of that contains about one inch of warm water. Avoid splashing the most common mistakes made is leaving the seedlings in the or excessive flooding, which might displace small seeds. When seed flat too long. The ideal time to transplant young seedlings the planting mix is saturated, set the container aside to drain. is when they are small and there is little danger from setback. The soil should be moist but not wet. This is usually about the time the first true leaves appear above Ideally, seed flats should remain sufficiently moist during or between the cotyledon leaves (the cotyledons or seed leaves the germination period without having to add water. One way are the first leaves the seedling produces). Don’t let plants get to maintain moisture is to slip the whole flat or pot into a clear hard and stunted or tall and leggy. plastic bag after the initial watering. The plastic should be at Seedling growing mixes and containers can be purchased least one inch from the soil. Keep the container out of direct or prepared similarly to those mentioned for germinating seed. sunlight; otherwise, the temperature may rise to the point at The medium should contain more plant nutrients than a ger- which the seeds will be harmed. Many home gardeners cover mination mix, however. Some commercial soilless mixes have their flats with panes of glass instead of a plastic sleeve. Be sure fertilizer already added. When fertilizing, use a soluble house to remove the plastic bag or glass cover as soon as the first seed- plant fertilizer at the dilution recommended by the manufac- lings appear. You can then surface-water if you do it carefully turer about every two weeks after seedlings are established. and use good judgment. Remember that young seedlings are easily damaged by too Manual watering, if not done uniformly, can result in plants much fertilizer, especially if they are under any moisture stress. being overwatered or drying out. Excellent germination and To transplant, carefully dig up the small plants with a knife moisture uniformity can be obtained with a low-pressure or wooden plant label. Let the group of seedlings fall apart misting system. In the spring, a satisfactory schedule might be, and pick out individual plants. Gently ease them apart in during the daytime, four seconds of mist every six minutes or 10 small groups, which will make it easier to separate individual seconds of mist every 15 minutes. Misting should be monitored plants. Avoid tearing roots, and handle small seedlings by their from time to time and the frequency adjusted to ensure that leaves, not their delicate stems. Punch a hole in the medium the medium is not waterlogged. into which the seedling will be planted. Make it deep enough Bottom heat is an asset with a mist system. As mist and water so the seedling can be put at the same depth at which it was in the medium evaporate, the medium is cooled. Bottom heat growing in the seed flat. Small plants or slow growers should will provide more uniform temperatures to aid germination. be placed one inch apart, and rapidly growing, large seedlings Sub-irrigation or watering from below can work well to keep the flats moist, but because the flats or pots are sitting in water 3-5 CHAPTER 03 Plant Propagation about two inches apart. After planting, firm the soil and water extends above the soil level, it may act as a wick and draw water gently. Keep newly transplanted seedlings in the shade for a few away from the soil in the pot. To prevent this, tear off the top days, or place them under fluorescent lights. Keep them away lip of the pot and then plant flush with the soil level. from direct heat sources, and continue watering and fertilizing Compressed peat pellets, when soaked in water, expand to as in the seed flats. form compact, individual pots. They waste no space, don’t fall Most plants transplant well and can be started indoors, apart as badly as peat pots, and can be set directly out in the but a few plants are difficult to transplant. These are generally garden. If you wish to avoid transplanting seedlings altogether, directly seeded outdoors or sown directly into individual con- compressed peat pellets are excellent for direct sowing. tainers indoors. Examples include zinnias and cucurbits such Community packs are containers in which there is room to as melons and squash. plant several plants. They are generally inexpensive. The main disadvantage of a community pack is that roots of individual plants must be broken or cut apart when separating the plants Propagation of Ferns by Spores to put out in the garden. Both community packs and cell packs are frequently used Though ferns are more easily propagated by other meth- by commercial bedding plant growers, as they withstand fre- ods, some gardeners like the challenge of raising ferns from quent handling. In addition, many homeowners find a variety spores. One tested method for small quantities follows: of materials from around the house useful for containers. These Put a solid, sterilized brick (bake at 250°F for 30 minutes) homemade containers should be deep enough to provide in a pan and add water to cover the brick. When the brick is adequate soil and have plenty of drainage holes in the bottom. wet throughout, squeeze a thin layer of moist soil and peat (1:1) onto the top of the brick. Hardening Plants Pack a second layer (about an inch) on top of that. Hardening is the process of altering the quality of plant Sprinkle spores on top. Cover with plastic (not touching the growth to withstand the change in environmental conditions spores) and put the plastic-encased brick in a warm place that occurs when plants are transferred from a greenhouse or in indirect light. It may take up to a month or more for the home to the garden. A severe check in growth may occur if spores to germinate. Keep the brick moist at all times. plants produced in the home are planted outdoors without a A prothallus (one generation of the fern) will develop first transition period. Hardening is most critical with early crops, from each spore, forming a light green mat. Mist the mat when adverse climatic conditions can be expected. lightly once a week to maintain high surface moisture; the Hardening can be accomplished by gradually lowering sperm must be able to swim to the archegonia (female parts). temperatures and relative humidity and reducing water. This After about three weeks, fertilization should have occurred. procedure results in an accumulation of carbohydrates and a Pull the mat apart with tweezers in one-quarter-inch thickening of cell walls. A change from a soft, succulent type squares and space the squares one-half inch apart in a flat of growth to a firmer, harder type is desired. layering two inches of sand, one-quarter inch of charcoal, This process should be started at least two weeks before and about two inches of soil/peat mix. Cover with plastic planting in the garden. If possible, plants should be moved to a and keep moist. 45° to 50°F temperature indoors or outdoors in a shady location. When fern fronds appear and become crowded, trans- A cold frame is excellent for this purpose. When put outdoors, plant them to small pots. Gradually reduce humidity until plants should be shaded, then gradually moved into sunlight. the fern plants can survive in the open. Exposure to light Each day, gradually increase the length of exposure. Reduce the may be increased at this time. frequency of watering to slow growth, but don’t allow plants to wilt. Don’t put tender seedlings outdoors on windy days or Containers for Transplanting when temperatures are below 45°F. Even cold-hardy plants will be hurt if exposed to freezing temperatures before they A wide variety of containers for transplanting seedlings is are hardened. After proper hardening, however, plants can be available. Containers should be economical, durable, and make planted outdoors and light frosts will not damage them. good use of space. The type selected will depend on the type The hardening process is intended to slow plant growth. of plant to be transplanted and individual growing conditions. If carried to the extreme of actually stopping plant growth, Standard pots may be used, but they waste a great deal of space significant damage can be done to certain crops. For example, and may not dry out rapidly enough for the seedling to have cauliflower will make thumb-size heads and fail to develop sufficient oxygen for proper development. further if hardened too severely. Cucumbers and melons will Containers made out of pressed peat can be purchased in stop growth if hardened. varying sizes. Individual pots or strips of connected pots fit closely together are inexpensive, and can be planted directly in the garden. When setting out plants grown in peat pots, be sure to cover the pot completely. If the top edge of the peat pot 3-6  Plant Propagation CHAPTER 03 Asexual Propagation Insert cuttings into a rooting medium such as coarse sand, vermiculite, soil, water, or a mixture of peat and perlite. It Asexual propagation is the best way to maintain some spe- is important to choose the correct rooting medium to get cies, particularly an individual plant that best represents that optimum rooting in the shortest time. In general, the rooting species. Clones are groups of plants that are identical to their medium should be sterile, low in fertility, drain well enough to one parent and can only be propagated asexually. The Bartlett provide oxygen, and retain enough moisture to prevent water pear (first selected in 1770) and Delicious apple (first selected stress. in 1870) are two examples of clones that have been asexually Moisten the medium before inserting cuttings, and keep it propagated for many years. evenly moist while cuttings are rooting and forming new shoots. Major methods of asexual propagation are cuttings, layer- Place stem and leaf cuttings in bright, indirect light. Root ing, division, and budding/grafting. Cuttings involve rooting a cuttings can be kept in the dark until new shoots appear. severed piece of the parent plant; layering involves rooting a part of the parent and then severing it; and budding/grafting Stem Cuttings is joining two plant parts from different varieties. Numerous plant species are propagated by stem cuttings. Some can be taken at any time of the year, but stem cuttings of Cuttings many woody plants must be taken in the fall or in the dormant season. Many types of plants, both woody and herbaceous, are fre- quently propagated by cuttings. A cutting is a vegetative plant Tip Cuttings part that is severed from the parent plant in order to regenerate Detach a two- to six-inch piece of stem, including the termi- itself, thereby forming a whole new plant. nal bud (Figure 3.3). Make the cut just below a node. Remove Take cuttings with a sharp blade to reduce injury to the parent lower leaves that would touch the medium or be below it. Dip plant. First, dip the cutting tool in rubbing alcohol or a mixture the stem in rooting hormone if desired. Gently tap the end of of one part bleach to nine parts water to prevent transmitting the cutting to remove excess hormone. Insert the cutting deeply diseases from infected plant parts to healthy ones. When making enough into the media to support itself. At least one node must cuttings, start with the youngest tissues and move toward older be below the surface. tissue. Re-dip (disinfect) the cutting tool each time you move to a new branch or a new plant. Remove flowers and flower buds Medial Cuttings from cuttings to allow the cutting to use its energy and stored Make the first cut just above a node and the second cut just carbohydrates for root and shoot formation rather than fruit and above a node two to six inches down the stem (Figure 3.3). seed production. To hasten rooting, increase the number of roots, Prepare and insert the cutting as you would a tip cutting. Be or to obtain uniform rooting (except on soft, fleshy stems), use a sure to position the cutting right side up. Axial buds are always rooting hormone, preferably one containing a fungicide. Prevent above leaves. possible contamination of the entire supply of rooting hormone by Cane Cuttings putting some in a separate container for dipping cuttings. Cut cane-like stems into sections containing one or two eyes, or nodes (Figure 3.4). Dust ends with fungicide or activated charcoal. Allow to dry several hours. Lay horizontally with about half of the cutting below the media surface, eye facing upward. Cane cuttings are usually potted when roots and new shoots appear, but new shoots from dracaena and croton are often cut off and re-rooted in sand. tip cutting medial cutting Figure 3.3. Two types of stem cuttings: tip and medial. (a)(a) (a) cane cane cane cutting cutting cutting (b)(b) (b) single-eye single-eye single-eye (c)(c) double-eye (c)double-eye double-eye (d)(d) (d) heel heel heel Figure 3.4. Other types of stem cuttings. 3-7  CHAPTER 03 Plant Propagation New plants will form at each cut. If the leaf tends to curl up, hold it in place by covering margins with rooting medium. Leaf Sections This method is frequently used with snake plant and fibrous-rooted begonias. Cut begonia leaves into wedges with (a) (a)whole wholeleaf leafwith withpetiole petiole (b) (b)whole wholeleaf leafwithout withoutpetiole petiole (c) (c)split-vein at least split-vein one vein. Lay leaves(d) (d)leaf leaf flat section onsection the medium. A new plant will arise at the vein. Cut snake plant leaves into two-inch sec- tions. Consistently make the lower cut slanted and the upper cut straight so you can tell which is the upper cut. Insert the cutting vertically. Roots will form fairly soon, and eventually a new plant will appear at the base of the cutting. These and other succulent cuttings will rot if kept too moist. Root Cuttings hout leaf without petiole petiole (c) split-vein (c) split-vein (d) leaf section (d) leaf section Root cuttings are usually taken from two- to three-year-old Figure 3.5. Types of leaf cuttings. plants during their dormant season, when they have a large carbohydrate supply. Root cuttings of some species produce Single-eye new shoots, which then form their own root systems, while root The eye refers to the node. This is used for plants with cuttings of other plants develop root systems before producing alternate leaves when space or stock materials are limited. Cut new shoots. the stem about one-half inch above and one-half inch below a The method of taking root cuttings depends on the root node. Place cutting horizontally or vertically in the medium. size, as follows: Double-eye Plants with Large Roots This is used for plants with opposite leaves when space or Make a straight top cut. Make a slanted cut two to six inches stock material is limited. Cut the stem about one-half inch above below the first cut. Store about three weeks in moist sawdust, and one-half inch below the same node. Insert the cutting verti- peat moss, or sand at 40°F. Remove from storage. Insert the cally in the medium with the node just touching the surface. cutting vertically with the top approximately level with the surface of the rooting medium. This method is often used Heel Cuttings outdoors (Figure 3.6). This method efficiently uses stock material with woody stems. Make a shield-shaped cut about halfway through the Plants with Small Roots wood around a leaf and axial bud. Insert the shield horizontally Take one- to two-inch sections of roots. Insert the cuttings into the medium. horizontally about 12 inches below the medium surface (Figure 3.6). This method is usually used indoors or in a hotbed. Leaf Cuttings Leaf cuttings are used almost exclusively for a few indoor Layering plants. Leaves of most plants will either produce a few roots Stems still attached to their parent plants may form roots but no plant or just decay (Figure 3.5). where they touch a rooting medium. Severed from the parent Whole Leaf with Petiole plant, the rooted stem becomes a new plant. This method of Detach the leaf and up to 1½ inches of petiole. Insert the vegetative propagation, called layering, promotes a high suc- lower end of the petiole into the medium. One or more new cess rate because it prevents the water stress and carbohydrate plants will form at the base of the petiole. The leaf may be shortage that plague cuttings (Figure 3.7). severed from new plants when they have their own roots and the petiole reused. Whole Leaf without Petiole This type of cutting is used for plants with sessile leaves. Insert the cutting vertically into the medium. A new plant will form from the axillary bud. The leaf may be removed when the new plant has its own roots. Split Vein Detach a leaf from the stock plant. Slit its veins on the lower (a) plants with large roots (b) plants with small roots leaf surface. Lay the cutting, lower side down, on the medium. Figure 3.6. Root cuttings. 3-8  Plant Propagation CHAPTER 03 (a) tip layering (b) simple layering (c) compound layering (d) mound layering (e) air layering Figure 3.7. Types of layering. Some plants layer themselves naturally, but sometimes plant propagators assist the process. Layering is enhanced by wounding one side of the stem or by bending it very sharply. Rooting medium should always provide aeration and a constant supply of moisture. Tip Dig a hole three to four inches deep. Insert the shoot tip and cover it with soil. The tip grows down first, then bends sharply Figure 3.8. Propagation using stolons. and grows upward. Roots form at the bend, and the re-curved tip becomes a new plant. Remove the tip layer and plant it in the early spring or late fall. Examples: purple and black raspberries, trailing blackberries. Simple Bend the stem to the ground. Cover part of it with soil, leaving the top six to 12 inches exposed. Bend the tip into a vertical position and stake in place. The sharp bend will often induce rooting, but wounding the lower side of the branch or loosening the bark by twisting the stem may help. Examples: Figure 3.9. A plant with offsets. rhododendron, honeysuckle. The following propagation methods can all be considered types of layer- Compound ing, as new plants form before they are detached from their parent plants: This method works for plants with flexible stems. Bend the stem to the rooting medium as for simple layering, but alter- Stolons and Runners nately cover and expose stem section, wounding the lower A stolon is a horizontal, often fleshy stem that can root, then side of the stem sections to be covered. Examples: heart-leaf produce new shoots where it touches the medium (Figure 3.8). philodendron, pothos. A runner is a slender stem that originates in a leaf axil and grows along the ground or downward from a hanging basket, Mound (Stool) producing a new plant at its tip. Plants that produce stolons or Cut the plant back to one inch above the ground in the runners are propagated by severing new plants from their par- dormant season. Mound soil over the emerging shoots in ent stems. Plantlets at the tips of runners may be rooted while the spring to enhance their rooting. Examples: gooseberries, still attached to the parent or detached and placed in a rooting apple rootstocks. medium. Examples: strawberry, spider plant. Air Offsets Air layering is used to propagate some indoor plants with Plants with a rosetted stem often reproduce by forming new thick stems or to rejuvenate them when they become leggy. Slit shoots at their base or in leaf axils (Figure 3.9). Sever new shoots the stem just below a node. Pry the slit open with a toothpick. from the parent plant after they have developed their own root Surround the wound with wet, unmilled sphagnum moss. Wrap system. Unrooted offsets of some species may be removed and plastic or foil around the sphagnum moss and tie in place. When placed in a rooting medium. Some of these offsets must be cut off, roots pervade the moss, cut the plant off below the root ball. while others may be simply lifted off the parent stem. Examples: Examples: dumbcane, rubber tree. date palm, haworthia, bromeliads, many cacti. 3-9 CHAPTER 03 Plant Propagation Separation Division Separation is a term applied to a form of propagation by Plants with more than one rooted crown may be divided and which plants that produce bulbs or corms multiply. the crowns planted separately. If the stems are not joined, gently pull the plants apart. If the crowns are united by horizontal Bulbs stems, cut the stems and roots with a sharp knife to minimize New bulbs form beside the originally planted bulb. Separate injury (Figure 3.11). Divisions of some outdoor plants should these bulb clumps every three to five years for largest blooms be dusted with a fungicide before they are replanted. Examples: and to increase bulb population. Dig up the clump after the snake plant, iris, prayer plant, day lilies. leaves have withered. Gently pull the bulbs apart and replant them immediately so their roots can begin to develop. Small, Grafting new bulbs may not flower for two or three years, but large ones should bloom the first year. Examples: tulip, narcissus. Grafting and budding are methods of asexual plant propaga- tion that join plant parts so they will grow as one plant. These Corms techniques are used to propagate cultivars that will not root well A large new corm forms on top of the old corm, and tiny as cuttings or whose own root systems are inadequate. One or cormels form around the large corm (Figure 3.10). After the more new cultivars can be added to existing fruit and nut trees leaves wither, dig up the corms and allow them to dry in indirect by grafting or budding. light for two or three weeks. Remove the cormels, then gently The portion of the cultivar that is to be propagated is called separate the new corm from the old corm. Dust all new corms the “scion.” It consists of a piece of shoot with dormant buds with a fungicide and store in a cool place until planting time, that will produce the stem and branches. The rootstock, or when both the new corms and the cormels can be planted. The stock, provides the new plant’s root system and sometimes the new corms are planted just like the previous corm and usually lower part of the stem. The cambium is a layer of cells located produce plants with bloom the first year. Cormels may take between the wood and bark of a stem from which new bark and more than one year to produce blooms and should be planted wood cells originate. (See Chapter 22, Growing Tree Fruits, for at a more shallow depth (about two inches) during the first year discussion of apple rootstock). and then planted as normal in succeeding years. Examples: Four conditions must be met for grafting to be successful: crocus, gladiolus. scion and rootstock must be compatible; each must be at the proper physiological stage; the cambial layers of the scion and stock must meet; and the graft union must be kept moist until the wound has healed. Cleft Grafting Cleft grafting (Figure 3.12) is often used to change the culti- var or top growth of a shoot or a young tree (usually a seedling). It is especially successful if done in the early spring. Collect scion wood three-eighths to five-eighths of an inch in diameter. Cut the limb or small tree trunk to be reworked per- pendicular to its length. Make a two-inch vertical cut through the center of the previous cut. Be careful not to tear the bark. Figure 3.10. Separating corms. side view top view cover surfaces with grafting wax Figure 3.11. Division. Figure 3.12. Cleft grafting. 3-10  Plant Propagation CHAPTER 03 Keep this cut wedged apart. Cut the lower end of each scion other materials. They expand with growth and usually do not piece into a tapered point similar in size to the wedge used to need to be cut because they deteriorate and break after a short hold the cut in the limb apart. Prepare two scion pieces three time. It is also an excellent idea to inspect grafts after two or to four inches long. Insert scions at the outer edges of the cut three weeks to see if the wax has cracked. If necessary, rewax in the stock. Tilt the top of the scion slightly outward and the exposed areas. The union will probably be strong enough after bottom slightly inward to be sure cambial layers of the scion this waxing, and no more waxing will be necessary. and stock touch. Remove the wedge propping the slit open, and Limbs of the old variety that are not selected for grafting cover all cut surfaces with grafting wax. should be cut back at the time of grafting. The total leaf sur- face of the old variety should be gradually reduced until the Bark Grafting new variety has taken over, which will take one or two years. Unlike most grafting methods, bark grafting (Figure 3.13) Completely removing all limbs of the old variety at the time of can be used on large limbs, although these limbs often become grafting increases the shock to the tree and causes excessive infected before the wound can heal completely. Collect scion suckering and may also cause scions to grow too fast, making wood three-eighths to one-half inch in diameter when the plant them susceptible to wind damage. is dormant. Store the wood wrapped in moist paper in a plastic bag in the refrigerator. Saw off the limb or trunk of the rootstock Budding at a right angle to itself. In the spring, when the bark is easy to separate from the wood, make a half-inch diagonal cut on one Budding, or bud grafting, is the union of one bud and a small side of the scion and a 11⁄2-inch diagonal cut on the other side. piece of bark from the scion with a rootstock. It is especially Leave two buds above the longer cut. Make two parallel upright useful when scion material is limited. It is also faster and forms cuts through the bark of the stock so that the width of the cuts is a stronger union than grafting. a little wider then the width of the scion. Remove the top third Patch Budding of the bark from this cut. Insert the scion with the longer cut Plants with thick bark should be patch budded, which is against the wood. Nail the graft in place with flat-headed wire done while plants are actively growing, so that their bark slips nails. Cover all wounds with grafting wax. easily. Remove a rectangular piece of bark from the rootstock. Whip or Tongue Grafting Cover this wound with a bud and matching piece of bark from Whip or tongue grafting (Figure 3.14) is often used for mate- the scion (Figure 3.15). If the rootstock’s bark is thicker than rial one-quarter to one-half inch in diameter. The scion and that of the scion, pare it down to meet the thinner bark so that rootstock are usually of the same diameter, but the scion may when the union is wrapped the patch will be held firmly in place. be narrower than the stock. This strong graft heals quickly and Chip Budding provides excellent cambial contact. Make one 21⁄2-inch sloping This budding method can be used when bark is not slip- cut at the top of the rootstock and a matching cut on the bottom ping. Slice downward into the rootstock at a 45° angle through of the scion. On the cut surface, slice downward into the stock one-quarter of the wood. Make a second cut upward from the and up into the scion so the pieces will interlock. Fit the pieces first cut, about one inch. Remove a bud and attending chip together, then tie and wax the union. of bark and wood from the scion that is shaped so it fits the Care of the Graft rootstock wound. Fit the bud chip to the stock and wrap the Very little success in grafting will be obtained without proper union (Figure 3.16). care for the following year or two. If a binding material such as strong cord or nursery tape is used on the graft, this tape must be cut shortly after growth starts to prevent girdling or constricting. Rubber budding strips have some advantages over scion scion rootstock rootstock Figure 3.13. Bark graft. Figure 3.14. Whip or tongue graft. Figure 3.15. Patch budding. Figure 3.16. Chip budding. 3-11 CHAPTER 03 Plant Propagation T-budding This is the most commonly used budding technique. When bark is slipping, make a vertical cut (same axis as the rootstock) through the bark of the rootstock, avoiding any buds on the stock. Make a horizontal cut at the top of the vertical cut (in a T shape) and loosen the bark by twisting the knife at the intersection. Remove a shield-shaped piece of the scion, including a bud, bark, and a thin section of wood. Push the shield under the loosened stock bark. Wrap the union, leaving the bud exposed (Figure 3.17). Care of Buds Place the bud in the stock in August. Force the bud to develop the following spring by cutting the stock off three to four inches above the bud. A new shoot will develop from the inserted bud, and other shoots may develop along the stem of the stock. Remove all buds from the stock except the one that arises from the inserted bud (scion). As the new shoot grows, it may be tied to the existing stub of the stock to prevent wind damage. The new shoot may be tied to the resulting stub to prevent damage from wind. After the shoot has made a strong union with the rootstock scion graft stock, cut the stub off close to the budded area. Figure 3.17. T-budding. Revised 01-2024