Plant Propagation Techniques for the Florida Gardener1 Sydney Park Brown2
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CIR579 Plant Propagation Techniques for the Florida Gardener1 Sydney Park Brown2 Most plants grown for Florida landscapes or as houseplants plants and placed in a warm, humid environment to hasten can be easily propagated. Home gardeners can thereby root development and prevent them from drying. increase the number of plants they have and decrease costs. There are two types of propagation techniques: sexual or asexual. Sexual propagation involves starting plants from seed, while asexual propagation involves multiplying plants from vegetative plant parts such as shoots, roots, and leaves, or specialized organs such as bulbs and corms. Information on budding and grafting propagation methods can be found in Propagating Fruit Crops in Florida (SP171) a for-sale booklet from the UF/IFAS Extension Bookstore (http://ifasbooks.ifas.ufl.edu/). Methods of propagating common Florida landscape plants Figure 1. Types of cuttings. are presented in Table 1. Additional information can be found in this online index: http://hort.ifas.ufl.edu/database/ STEM CUTTINGS lppi/index_scientific.shtml#G. Stem cuttings consist of just the growing tip of a plant or stem sections below the tip (Figure 2 and Figure 3). The Asexual Propagation age of the stem is important because some plants root The most important reason to use asexual propagation is to better from new tender stems, while others do best with reproduce plants with the same characteristics as the parent more mature tissue. These stages of stem growth are called plant. It is especially useful for plants that are difficult or softwood, semi hardwood, or hardwood. Softwood and impossible to propagate from seed. semi-hardwood cuttings are from the current season’s growth, and hardwood cuttings (seldom taken in Florida) Cuttings are from the previous season’s growth. Softwood cuttings The most common asexual method is cuttage. Cuttings can are generally taken in spring or early summer when plants be made from stems, roots, leaves, or combinations of plant are producing soft, succulent new growth. Semi-hardwood parts (Figure 1). Cuttings should be taken from healthy cuttings are taken after a growth flush has matured. Stems of semi-hardwood cuttings will usually “snap” like green 1. This document is CIR579, one of a series of the Environmental Horticulture Department, UF/IFAS Extension. Original publication date January 1990. Revised March 1991 and February 2016. Reviewed March 2019. Visit the EDIS website at https://edis.ifas.ufl.edu for the currently supported version of this publication. 2. Sydney Park Brown, associate professor emerita; UF/IFAS Extension, Gainesville, FL 32611. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office. U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension. beans when broken. Many Florida plants root best as quantities can be sterilized by placing a 2-inch (5-cm) layer semi-hardwood cuttings. of moist medium on a tray in an oven or barbeque grill at 220°F (104°C) for 1 hour. (Warning: the odor may be offensive.) Rooting can be enhanced with commercially available products called rooting hormones. The bottom ½ inch (1.2 cm) of the cuttings are dipped into the product before sticking them in a medium. These commercial preparations are available at most garden centers in various concentrations, suited for easy-, moderate-, or difficult-to- root plants. Some talc formulations also contain a fungicide to protect the cutting from disease. LEAF CUTTINGS A leaf cutting (Figure 4) may be comprised of only the leaf or the leaf and petiole (leaf stem). Begonias and African Violets are commonly propagated this way. Stick leaf cuttings upright in the propagation medium making sure the basal end of the cutting is inserted into the propagation Figure 2. Tip cutting. medium. Roots and new shoots will start at the base of the leaf. Leaf cuttings of some plants, such as the Rex begonia, are first wounded by cutting the underside of the main veins before placing the leaf surface flat and in firm contact with the propagation medium. Sometimes it is helpful to pin these leaves to the moist medium with small stakes or toothpicks. New shoots and roots will emerge where the veins were cut. Figure 3. Subterminal stem cutting. Stem cuttings are removed using a clean, sharp knife or pruner. Cuttings 4 to 6 inches (10 to 15 cm) in length are appropriate for most plants. Leaves are removed from the bottom 1 inch (2.5 cm) of the stem and the cuttings are then stuck upright in a medium (i.e., soil mixture/substrate) just deep enough to hold them upright, usually ½ to 1 inch Figure 4. Leaf cutting. (Begonia) (1.2 to 2.5 cm). LEAF-BUD CUTTINGS A mixture of equal volumes of peat moss and coarse perlite Leaf-bud cuttings include the leaf, the petiole, the axial is a suitable rooting medium for most plants, but combina- bud, and a ½- to 1-inch (1.2- to 2.5-cm) segment of the tions of other materials such as shredded peat, vermiculite, stem (Figure 5). Every joint (node) can be used as a cutting. sand, and coir are also satisfactory. The medium should When the stem roots, the axial bud produces a new shoot. drain freely and be free of disease, organisms, and weed seed. Packaged sterile media can be purchased, or small Plant Propagation Techniques for the Florida Gardener 2 HARDENING ROOTED CUTTINGS The rooting period will vary from 2 to 16 weeks depending upon plant species, the condition of the cuttings, and the rooting environment. New leaves and roots of rooted cut- tings typically need to be “hardened” before transitioning to containers or the landscape. The first step in hardening is to decrease the humidity either by increasing the time between mistings (if a mist system was used) or by increasing the air flow around the cuttings (if an enclosed rooting structure was used). After a gradual decrease in humidity, the light intensity can be slowly increased by moving the plants into areas receiving increasing amounts of sunlight. Plants that are not Figure 5. Leaf-bud cutting. adequately hardened are less likely to survive transplanting. ROOT CUTTINGS Layering Root cuttings (Figure 6) are usually taken from plants in early spring or late winter before they start growing. At this Layering is a relatively easy method of asexual propagation time of year, healthy roots have ample stored food (carbo- by which new plants are formed while attached to the hydrates) that will support root development. Root cuttings parent plant. The new plant receives nutrients and water are typically 2 to 7 inches (5 to 18 cm) in length depending from the parent plant until roots develop. This method of upon root diameter. Large roots can be cut shorter than asexual propagation yields a large plant in a relatively short small roots and still have an adequate food supply for root time and is an excellent way to produce a small number of and shoot growth. Small, delicate root cuttings (⅛ to ¼ plants in the home landscape or to propagate plants that are inch or 3.2 to 6.4 mm in diameter) should be positioned difficult to increase by other methods. Layering outdoors is horizontally in the propagation medium and covered with best performed during spring and summer although it can ½ inch (12 mm) of medium. Larger root cuttings (¼ to ½ be done during any season of the year. Spring and summer inches or 6.4 to 12.8 mm in diameter) can be planted verti- layers are usually rooted and ready for transplanting in the cally with the end of the cutting originally nearest the plant fall or winter. crown positioned upward. Optimum temperatures for most root cuttings range from 55°F to 65°F (13°C to 18°C). Root Healthy branches that are growing vigorously in adequate cuttings may be transplanted after shoots have emerged sunlight should be chosen for layering since these usually and sufficient new secondary roots have developed. The have more food reserve (carbohydrates) and therefore root principal disadvantage of this method is the amount of faster. Branches from pencil size to about ¾ inch (2 cm) in digging involved in obtaining the root cuttings. diameter are best for layering. The various types of layering are air, tip, trench, mound, and serpentine. AIR LAYERING Air layering is commonly used to reproduce fiddle-leaf figs, rubber plants, crotons, hibiscus, calliandra, oleanders, camellias, azaleas, and magnolias. The stem is wounded and encased in moist sphagnum moss into which roots grow. Once an adequate root system has been produced, the rooted stem is cut from the parent plant. The air layer is usually made at least 12 to 15 inches (30 to 38 cm) below the tip of the branch. The first step is to remove leaves and twigs for 3 to 4 inches (8 to 10 cm) above and below the point where the air layer is to be made (Figure 7). Figure 6. Root cutting. Plant Propagation Techniques for the Florida Gardener 3 One method consists of removing a ½ to 1 inch (1 to 3 propagated by this method. A low branch, or one that can cm) ring of bark and, with a knife, scraping clean the wood be bent easily to the ground, is chosen.