Plants can be propagated by sexual or asexual means. Sexual propagation is starting plants from seed. Multiplying of plants from vegetative plant parts such as shoots, roots and leaves or bulbs and corms is called asexual propagation.
Asexual propagation will grow plants with the same characteristics as the parent plant. It is the best method of reproduction when a plant produces seeds which are difficult to germinate. The most common method of asexual propagation is from cuttings. Cuttings can be made from stems, roots and leaves. Cuttings should be taken from healthy plants and placed in a warm, humid environment to encourage root development and prevent them from drying.
Stem cuttings can be taken at different stages of vegetative maturity, from just the growing tip of a stem or stem sections, depending on the plant being propagated. Softwood cuttings are generally taken from plants in spring or early summer during a growth flush when tissue is soft and succulent. Semi-hardwood cuttings are taken after a growth flush has matured.
Stem cuttings are removed using a clean, sharp pruner. Cuttings should be four to six inches in length. Remove the leaves from the bottom one inch of the stem cuttings and then stick them just deep enough to hold them upright into a medium suitable for propagation. A mixture of equal parts of peat moss and course pearlite is a suitable rooting medium for most plants. Combinations of other materials such as shredded sphagnum, vermiculite and sand will also do. The medium should drain freely and be free of disease and weed seeds. Root promoting chemicals can be applied to the ends of cuttings before sticking them in the medium to enhance rooting. These rooting hormone preparations are available at most garden centers.
Leaf cuttings might be only the leaf blade or the leaf blade and petiole (leaf-stem). Begonias are commonly propagated by leaf cuttings. Leaf cuttings are cut on the underside of the main veins then placed flat and in firm contact with the medium. It can be helpful to pin the leaves in place with small stakes or toothpicks. Or, leaf cuttings can be stuck upright in the medium making sure the basal end of the cutting is inserted into the medium. Roots and new shoots will start at the base of the leaf or at points where veins were cut.
Leaf bud cuttings include the leaf blade, the petiole and one inch of the stem. Auxillary buds located at the union of the petiole and stem produce new shoots when in warm and humid conditions. This method is used for plants in short supply that have long inter-nodes since every node on the stem can be a cutting.
Root cuttings are taken from young plants in late winter or early spring, before they start growing. Healthy roots will have ample food stored to support shoot development at this time. Cuttings are usually two to seven inches long. Small root cuttings should be put horizontally in the medium and covered with one half inch of medium. Larger root cuttings can be planted vertically with the end of the cutting that was originally nearest the plant crown positioned upward. The best temperatures for most root cuttings range from 55F to 65F.
Layering is an easy method of propagation by which new plants are formed while attached to the parent plant. The new plant receives nutrients and water from the parent plant until roots develop. Healthy, maturing branches that are growing vigorously should be chosen for layering since these have more food reserve and root faster. Branches from pencil size to three quarters inch in diameter are best for layering. Wood that would normally be pruned while shaping the plant is often suitable for layering. Various types of layering are air, tip, trench, mound and serpentine. Air and tip layering are the most popular methods.
Air layering is commonly used for propagation of fiddle-leaf figs, rubber plants, crotons, hibiscus, oleanders, camellias and azaleas. The first step is to remove leaves and twigs on the selected limb for three to four inches above and below where the air layer is to be made. This is usually made a foot to a foot and a half below the tip of the branch. The branch is wounded by either removing a one inch ring of bark and scraping clean the wood underneath or by making a long slanted cut upward about half way through the twig. This incision should be kept open with a small chip of wood or toothpick to prevent the cut from healing over. The wounded area should be bound with a handful of moist, but not wet, sphagnum moss. Tie the moss firmly in place and wrap the sphagnum ball with clear plastic and tie securely above and below the ball to prevent the moss from drying. Cover with aluminum foil to prevent excessive heat build up from the sun. When a mass of roots has developed in the sphagnum ball (one month to one year) the layered branch can be removed from the parent plant. Before planting the new plant in the garden it is best to allow the plant to develop a larger root system in a container or protected area to avoid high light and dry conditions.
Tip layering is good for propagating climbing roses, jasmine, oleander or pyracantha. Most vines can be propagated using this method. A low branch, or one that can be bent to the ground, has a one inch wound applied four to five inches from the tip. The wounded area is anchored two to three inches in the soil. It is once again important to keep the soil moist. The layered section should have roots before removal from the parent plant.
Trench and serpentine layering are similar to tip layering except that a longer branch is placed in a trench and covered with soil. These methods produce several new plants from each layered branch. Trench layering is useful on plants whose buds will break and grow under the soil surface such as willows, viburnum and dogwood. Serpentine layering involves burying every other bud, leaving the alternate bud above ground. This method requires plants with pliable, vine-like stems such as grapes and confederate jasmine.
Mound layering can be used to propagate heavy stemmed or closely branched plants such as crotons or tibouchina. Mound layering is started in the spring. The plant is cut back severely just before spring growth. The new shoots that emerge are wounded and soil is mounded around the base of the plant in several stages about one and a half feet. Add peat or sphagnum moss to the mounding soil to help removing rooted branches. It takes about one growing season to produce shoots that have rooted sufficiently for transplanting.
Plants with a multi stem or clumping habit of growth, off shoots, or with underground storage structures such as rhizomes or tubers can be propagated by division. This involves cutting large clumps into smaller sections, making sure each section has as adequate amount of stems, leaves, roots and buds to survive transplanting. Ferns, orchids, daylilies, bulbous plants and lariope can be propagated this way. Some plants can be pulled apart but many must be cut. Do not divide plants when they are flowering, but any other time of the growing season is fine.
And the last and least expensive way to produce large numbers of new plants is seed propagation. A disadvantage of this method of propagation is that seedling characteristics are usually quite variable. Seed propagation is a means of reproducing plants that are extremely difficult or impossible to propagate vegetatively. Most palms are grown from seed because they are single stemmed and cuttings cannot be taken without destroying the parent plant.
The sooner you start propagating the sooner you’ll enjoy some new plants for your landscape.
Eileen Ward and her husband Peter have owned and operated Greensward of Marco, Inc., a lawn maintenance and landscaping company since 1981. Watch Eileen’s gardening videos on MarcoIsland-TV.com.