Part 1 of "Plant Propagation" briefly discusses reasons why we use sexual (seed) or asexual (vegetative) propagation to reproduce new plants. Part 2 describes some of the methods used to reproduce new plants using vegetative propagation. Many plants can be reproduced by using more than one method of vegetative propagation. Examples of these will be listed in the final series on "Plant Propagation". Air-Layering
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Air-layering is used to reproduce new compact plants when bottom leaves have dropped off of a plant, resulting in a tall, overgrown specimen with only a few leaves left near the top of the plant. This method of propagation is used on thick-stemmed plants like Ficus elastica (Rubber Plant); Dieffenbachia (DumbCane); Monstera deliciosa (Swiss Cheese Plant); Dracaena spp. ; Cordyline spp. ; Croton spp. and all cultivars of the above named plants, among others. This type of propagation also goes by the names of ringing, Chinese-layering, circumposition, stem-layering and mossing.
The first step in air-layering is to choose a spot on the stem less than 2 feet from the tip (top) of the plant where the air-layering will be done. The top part will be the new plant, so be sure that portion looks like a nice, new plant. If possible, there should be at least 4-5 leaves on the top section.
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Using a sharp knife, make a horizontal cut about 1/3 of the way through the stem (preferably just below a node) where you want the roots to be on your new plant. Now, from the end of that cut, turn the knife upwards and slice straight up through the stem about 1(one) inch. The cut should look like the capital letter L when it is finished. Once the cuts are made, force a piece of wooden match stick sideways through the upright cut to keep the layers separated so as they will not heal together again. A rooting hormone powder may be dusted on the two surfaces to help induce rooting, but is not necessarily required.
The next step is to tie one or two handfuls of moist, long fibered sphagnum moss around the stem where the cut is made. The new roots will grow into this moss. The sphagnum moss must only be moist, not wet. A good way to make sure it is moist is to let it soak up all the water it can hold, and then squeeze out as much water as you possibly can with your hands. The moss can now be tied in place around the cut with string. Short fibered moss may also be used , its just a little harder to hold it in place.
The final step is to wrap a clear piece of plastic (a plastic bread-bag will work) around the moss and secure it by tying the top and bottom with string. The plastic keeps the moss moist while the roots are forming and enables you to see the roots once they have formed. The sphagnum moss must not be allowed to dry out during the rooting period. If it has been sealed properly, it generally does not require additional moisture.
Continue to care for the plant as before by watering and feeding it. New roots should develop in 6-8 weeks (or longer) and be clearly visible through the plastic. When several roots are visible, the plant is ready for potting. Choose an appropriate sized pot for the new plant and have the potting soil ready. Remove the plastic, cut the stem off just below the roots and pot up the new plant. Don't try to remove too much of the moss from the root-ball or the delicate new roots may be damaged. Water the plant well and set it in a dimmer light than it normally requires for a couple of days. If you continue to look after the old stem, it may send out new shoots from dormant buds near the top of the stem which can be air-layered at a later date.
Air-layering can also be used out of doors to propagate new shrubs like lilacs (Syringa), for example. Tape should be wrapped around the top and bottom of the plastic to prevent rain water from getting into the moss and making it too wet. A simple upward cut on a slight angle and about 1/3 of the way through the stem is all that is required. The layers must be kept apart using a piece of matchstick as above. These layers can be dusted with a rooting hormone to help induce rooting. Provide shade for the air-layered portion of stem if it happens to be facing the sun. The hot sun can burn the roots or dry out the moss.
Layering, Soil Layering, Ground Layering
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Although this type of vegetative propagation is most often used with climbing vines or trailing plants, many other plants with soft, flexible stems can be layered. It is one of the slower methods of propagation because rooting takes a considerable amount of time. Plants commonly layered include: Hedera helix (Common or English Ivy); Senecio mikanioides (German Ivy); Senecio macroglossus (Cape Ivy); Hoya spp. (Wax Plant); Scindapsus (Devil's Ivy); Syngonium (Arrowhead Vine); Cissus antarctica (Kangaroo Vine); Rhoicissus rhombifolia (Grape Ivy); Jasminum (Jasmime); Gardenia (Gardenia) ; all their cultivars, and other plants.
The best time to use this technique is in the spring or early summer. Choose a healthy, vigorous stem and make a notch about half way through on the underside of the stem about 4-8 inches from the tip of that stem. This notch may be dusted with a rooting hormone powder. The next step is to pin it down (use a U shaped piece of wire turned upside down or a hair pin) onto a pot of moist potting media that is located next to the parent plant. Cover the notched area with ½ inch of media, leaving the end of the stem exposed. Once new growth appears at the end of the stem or near the notch, or gentle tugging indicates the stem has rooted, the stem attaching the new plant to the parent plant may be severed.
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Out of doors, soil layering works equally as well with many shrubs and some trees. There may have been a time when you have tried to pull up a branch that was laying on the soil only to find it was rooted firmly to the ground. Soil layering basically works in the same manner. Trees or shrubs with flexible (bendable) shoots or stems are the easiest to work with. One year old stems root the easiest, although older stems will also root.
All that is required is to choose a healthy stem (leave it attached to the plant) and bend it over so it will touch the soil. The soil should be loose and friable. Make a slight-angled notch or slit on the underside of the stem (about ½ way through the stem) where it touches the soil. If the stem is 2 feet long, make the notch 10 to l2 inches from the tip of the stem. Dig a hole about 3-4 inches deep and bury the notched part of the stem, pegging it down with wire so it remains buried. Keep the soil moist and weed free. Let the plant remain as such for at least one season. The following spring, the plant can be severed from the parent plant (as long as it has rooted well the previous season) and moved to its permanent location. Try to leave some soil on the roots when you move it. Mulch the soil around the new plant with a 3 inch layer of organic matter and keep it watered while it is re-establishing.
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Trees and shrubs that are easy to layer include: Salix (Willows); Populus (Poplars); Ribes (Currants and Gooseberries); Cotoneaster; Forsythia; Cornus (Dogwood); Syringa spp. (Lilac); Spiraea and Juniperus (Junipers), for examples.
Serpentine layering is the term used for layering plants with long vines. Clematis and Parthenocissus (Virginia Creeper) are often reproduced using this method of vegetative propagation. A long shoot is laid along the soil in a snakelike pattern. Every 2nd node is then slit on the underside to form a slight tongue in the shoot. These nodes are then buried and pegged down with wire while the alternate ones are left exposed on the soils surface. New shoots eventually develop on the exposed nodes while roots form on the buried ones. After a season or two, once good roots have developed, the shoots are severed to form individual plants.
Plantlets, Stolons, and Runners
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These methods of vegetative propagation are grouped together because new plants are basically reproduced in the same way. A plantlet is a small plant which grows on the end of a flowering stem (Chlorophytum -Spider Plant for example), or on the edges of mature leaves (Kalanchoe daigremontianum-Devils BackBone) and exactly resembles the parent plant.
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Stolons and runners differ in that stolons run under the soil and produce new plants at their tips, whereas, runners run on top of the ground and produce new plants at joints along the runner. Cornus stolonifera (Red-Osier Dogwood); Spiraeas and Sorbaria sorbifolia (Falsespirea) are examples of plants that produce new plants by means of stolons. The familiar and well known Fragaria (Strawberry) is a plant that produces new plants by means of runners. New plants from stolons can be severed from the parent plant, dug up and transplanted once top growth is of sufficient size. Runners will root themselves, or they can be set into the soil and pegged down to speed up the rooting process. Once they develop a good root system, they can be severed from the parent plant and transplanted.
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Plantlets provide the easiest means of reproducing new plants. Baby Spider plants are often removed from the parent plant and set in water to increase the length of their already visible roots before potting them on. New plants can be reproduced by simply pining down the plantlet in a pot of moist potting media and cutting it free from the parent plant once it is well rooted. Other plants reproduced by plantlets include: Tolmiea menziesii (Piggy Back Plant); Episcia dianthiflora (Lace Flower); Duchesnea indica (Indian Strawberry); and Saxifraga sarmentosa (Mother of Thousands, Strawberry Begonia). The small plantlets that form on the edges of leaves like Kalanchoe daigremontianum produce roots on their little plantlets and only need to be set on moist potting soil to start new plants.
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Another houseplant that produces new plants from runners is Nephrolepis exaltata bostoniensis (Boston Fern). Simply pin down the wiry runners (leave attached to the parent plant) onto pots of moist soil in early spring and wait until the new plants take root, at which time the runners can then be cut away. If you reproduce more plants than you need, friends are often happy to accept them.
