Sooner or later, most of us who grow house plants become interested in the propagation of those plants; in other words, taking cuttings to produce more plants. It’s only natural. If you’re the kind of person who enjoys nurturing living, growing things, like plants, chances are you’ll want to take that next step – propagation – so you can share your happy plants with friends or family members, or simply to see whether or not you can actually do it. Perhaps you’ve got a vigorous philodendron plant that threatens to obliterate the light from a window, or a healthy dracaena plant that’s about to grow through the ceiling. You can’t bear the thought of cutting it back and throwing away any part of a healthy living plant, one that you’ve taken such good care of. So vegetative propagation of the plant is your likely impulse.
“Vegetative propagation?” you may ask. Vegetative, in this case, simply means ‘non-sexual’. Sexual propagation is propagation by means of seeds. A flower is pollinated, a seed is formed (perhaps inside a fruit), the seed germinates and a new plant is born. It’s nature’s usual mechanism for reproduction of the species. Vegetative, or asexual, propagation is reproduction by any other means, such as by layering or cuttings, used to create new individual and self-sufficient plants. Vegetative propagation generates new and relatively mature plants without waiting for seeds to sprout and seedlings to grow. It’s also useful for reducing the size of overgrown specimens. For house plants, there are several effective methods of propagation that may be used, depending on the type and the physical form of the plant to be propagated.
The easiest and probably the most common way of propagating house plants is by cuttings. There are several types of cuttings that work well, again depending on the type of plant in question. Stem cuttings are good for plants that grow on vines, such as philodendrons, pothos, hoyas, ivies, and similar plants. Using a sharp knife or bypass-style pruning shears, cut a section of the vine or stem that includes at least 4 to 6 nodes (the nodes are the places on the stem at which the leaves are attached). Cuttings may be taken from the growing end of the stem or from anywhere along it. Strip the leaves away from the bottom node or two. In most cases, new roots will emerge from the nodes.
Stem cuttings may be rooted in either water or a sterilized potting medium. Cuttings with fairly slender stems will root easily in plain water. Use tap water that has been left to sit out for 24 hours or more to allow chlorine and fluorine gasses to dissipate. Place the fresh cuttings into a glass or jar of the water, submerging the exposed nodes but not allowing any foliage to be in the water. It can be helpful to drop a clear plastic bag over the cuttings and the glass to increase humidity while the stems are rooting. Don’t seal the bag, however, as air circulation must be present to avoid rotting. The bag can be supported over the cuttings with wood plant stakes or dowels, so air can circulate from underneath. Place the cuttings in bright, indirect light away from full sun while they are rooting. Change the water as necessary to keep it clear and oxygenated, and add water to replace any that has evaporated or been used by the plants. In most cases, roots should start to appear within 3 to 4 weeks.
Roots formed in water may appear sooner than those formed in soil, but they may not be as sturdy and may have a more difficult time adjusting to being transplanted. Therefore, many growers prefer to propagate cuttings by rooting them in a sterile potting medium or soil mix. Sterilized growing mixes can usually be purchased at a garden center. Otherwise, a mixture of half sand and half peat moss is good for rooting most cuttings. Sterilize it by putting it into a 300-degree oven for an hour. Then moisten it before using. Stem cuttings should be dipped into a powder containing a rooting hormone and a fungicide (available from a garden center) before inserting into the growing medium. Insert the stem deeply enough so that the exposed nodes are covered. Keep the medium moist but never soggy. Maintain high humidity, perhaps by using a plastic bag as above or by frequent misting with water. Place the cuttings in bright, indirect light. After 5 or 6 weeks, cuttings should be ready for transplanting.
After cuttings have rooted, they must be planted into a regular soil mix. Remember that their propagation media have had no nutritional value, so the new potting soil should be one that contains some amount of organic matter to provide nutrients. Once the cuttings are established in their new pots, after a couple of months or so, begin fertilizing with an ordinary house plant food at one-half the normal dilution rate.
Larger plants with heavier stems, such as dieffenbachias, Chinese evergreens, larger philodendrons, some dracaenas, etc., may also be propagated by stem cuttings. In this case, cut the stem with about 6 or 7 leaves from the top of the plant. You can also cut similar sections of stem from further down. As before, remove 2 or 3 leaves from the bottom of the cutting, exposing the nodes. Cut the upper half away from each remaining leaf blade so as to reduce moisture loss during propagation. Dip the bottom end of the cutting into rooting powder. Then set the cutting aside for a week or so, in a bright but shaded spot, allowing the cut end to callus (similar to forming a scab) to keep the cutting from drying out too much and from rotting as it takes root. Once the callus has formed, insert the stem cuttings into a sterile potting medium as mentioned before until they’ve rooted.
Another, perhaps simpler way of propagating vining plants is by layering. In this process, a section of the long stem of the plant is simply pinned to the soil, without separating it from the original plant, until it grows roots. Using a U-shaped or hairpin-like wire, pin one or more nodes of the original vine to the surface of the potting soil, which is kept constantly moist but not soggy. You can pin the vine back into the original pot or onto the moist soil in a new, nearby separate pot. Once the layered stems have taken root, simply cut the stem behind the freshly rooted nodes and pot the cuttings separately. If you have enough vines and they’re long enough, you may be able to pin several stems together into a new pot and create a whole new plant all at once.
Some house plants may be propagated by leaf cuttings. These include African violets, begonias, peperomias, and most succulent plants, such as aloe vera, jade plant, kalanchoe and sansevieria. Using a sharp, clean knife, cut the leaf including any stem (the leaf petiole) from the main plant. Dip the cut end in rooting powder. For soft or slender stems like begonias and peperomias, insert the petiole immediately into the rooting medium, nearly up to the base of the leaf without touching it. For thicker leaves, like African violets, allow the cut end to callus for 2 or 3 days before inserting. Succulent leaves, including jade plant, aloe, and similar plants, should callus at least a week before propagation; otherwise the cuttings will tend to rot. Do not supply any extra humidity for succulents, again to avoid rotting from too much moisture.
For very heavy or woody-stemmed plants, such as rubber trees, dracaenas, and large dieffenbachias, a propagation technique called ‘air layering’ is best. Air layering allows a large cutting to take root before being separated from its mother plant, ensuring against loss of the cutting before it’s rooted. Using a sharp knife, cut a narrow, V-shaped notch halfway into the stem at the point where you want roots to form. This should be immediately below a node from which the leaf (or several leaves) has been removed. Brace the notch open with a pebble, a short stick or a piece of toothpick to prevent it from healing closed. Dust the cut with rooting powder. Wrap the area in and around the notch, all the way around the stem, with damp sphagnum moss. Depending on the size of the plant, you should wind up with a ball of sphagnum moss approximately the size of your clenched fist. Wrap the damp moss with clear Saran or similar plastic wrap. Secure the wrapping above and below the wad of moss with twist-ties. The moss should stay damp throughout the rooting process (from 4 to 8 weeks). If it tends to dry out, gently add water from the top to re-dampen the moss. When vigorous roots are visible through the plastic wrap, cut the new plant below the roots, remove the wrap and plant the cutting in its own pot. The original plant will send out one or more new shoots from below the point where the cutting was removed.
Air layering is an excellent propagation technique to use when the original plant has become tall and leggy. The layering can be done at two or three points along the stem, and when all have rooted, they may be planted together, along with the original if desired, to create a new and much fuller plant. It’s best to begin this process in the spring when growth is more active.
We hope this column has answered some of your questions regarding house plant propagation. Remember to consult your local professional florist for more details about these and other techniques, and how best to apply them with specific kinds of plants. It’s fun to grow more house plants from the ones you already have! In the immortal words of this well-known phrase, “Go forth and multiply!”
