Most gardeners rely on two proven vegetative (asexual) propagation methods to create new plants: cuttings and divisions. Both approaches involve severing stems, leaves, or roots from the “parent” plant and then tending the severed parts as they develop new root systems of their own. These methods aren’t complicated, but they do take some practice to master and occasional failures are to be expected.
A third vegetative propagation method, layering, is not as familiar to home gardeners, yet it has existed in nature for probably as long as plant species have inhabited the earth. Like cuttings and divisions, layering produces new plants with characteristics identical to those of the parent plant. Unlike cuttings and divisions, this method creates a new plant while it is still attached to the parent plant. A “layer” is the name given to a rooted plant after it is detached from the parent plant. Until it is detached, the layer benefits from being supplied with nutrients and moisture while it develops an independent root system. As a result, this propagation method generally has a higher success rate than plants started from cuttings or divisions.
LAYERING AS A VEGETATIVE PROPAGATION METHOD
Layering is best suited for propagating shrubs, vines, woody herbs, and even some trees that have flexible stems located low to the ground. It’s a good alternative to stem cuttings for some plant species that are difficult to propagate. Layering is also a good method for propagating native species that aren’t readily available for sale through commercial sources. It is not normally suitable for propagating herbaceous perennials or annuals.
While plants may be layered any time of year, dormant stems are best rooted in late winter to early spring just before new growth starts. This allows the layer to develop a good root structure over the summer and plenty of time to get established after it is separated from the parent and transplanted elsewhere.
HOW MOTHER NATURE DOES IT
Many plant species evolved to replicate themselves naturally through offsets, stolons or runners, and suckers, all of which are specialized plant structures. Because these structures result in new plants while they still attached to the parent plant, they are considered to be a form of layering.
Offsets – Sideshoots or branches that grow from buds at the base or main stem of a plant. After they have developed their own root systems, offsets (which are often called pups) can be propagated by simply cutting them away from the plant parent and planting them. Agave and yucca are examples of landscape plants that can be propagated from offsets. Some houseplants, such as Chinese money plant (Pilea peperomioides) and aloe, may also be propagated from offsets.
Stolons (Runners) – Stems that emerge from the crown of a plant and grow horizontally above the soil surface. New plants can form from nodes along the stem. If the nodes come in contact with soil, they develop roots and top growth resulting in a new plant. Strawberry plants, many ground covers, grasses, and some weeds replicate themselves using stolons.
Suckers – Stems that develop from root tissues below ground or from stem tissue at the base of a plant. On the one hand, plants that sucker can be a nuisance, especially if the suckers allow the plant to spread beyond the space allocated for it in the landscape. On the other hand, rooting suckers as a propagation method allows gardeners to duplicate desired plants repeatedly without significant variation from the parent plant. Examples of native shrubs that sucker include Virginia sweetspire (Itea virginica), sweet pepperbush (Clethra), spicebush (Lindera benzoin), and witch alder (Fothergilla).
METHODS FOR LAYERING PLANTS
Many plant species do a remarkable job of propagating themselves through the specialized plant structures just described. They are the inspiration for a variety of layering techniques now used by professional plant propagators and home gardeners. For simple drawings of these techniques, see the link to the Virginia Cooperative Extension Gardener Handbook (page 222) under Sources below.
Before starting a layering project, take a few minutes to decide which of the five basic methods described below is best for the plant being layered.
Technique 1 – Tip Layering – This is a particularly easy way to propagate vining plants such as purple and black raspberries and blackberries. The technique involves rooting the tip of the current season’s growth where the greatest concentration of rooting hormones is located. To tip layer a plant:
- Select a long arching stem and bend it so that the tip touches the ground.
- Dig a shallow 3” to 4” deep hole at that spot, insert the tip into the hole and cover it with soil.
- If necessary to hold the tip in place, secure it with a U-shaped pin or piece of wire or simply use a rock. The tip will initially grow downward but will bend sharply upward toward the light. Roots will form at the bend and the recurved tip will become a new plant.
- Keep the soil moist while the roots are developing.
- Note: If this is more convenient, root the stem tip in a pot filled with potting soil rather than in the ground.
Technique 2 – Simple Layering – This method works well for plants with flexible low-growing branches such as abelia, azalea, boxwood, dogwood, forsythia, Virginia sweetspire and rhododendron.
- In late winter to early spring, select a young, flexible stem near the base of the plant. Make sure the stem will bend to the ground without breaking.
- Select a spot about 6” to 12” from the tip of the stem for layering. At that spot, dig a shallow 3” to 4” deep hole.
- Remove the leaves from the part of the stem that will be buried.
- Use a sharp knife to slice off a portion of the bark from the underside of the stem.
- Optional: Although not necessary, dusting a rooting hormone (auxin) to the wound can facilitate rooting.
- Bend the stem down so that the wounded area is at the bottom of the prepared hole. This is the point where new roots will form.
- Secure the stem in place with a U-shaped landscape staple or set a rock or brick on it to keep it beneath the soil.
- Leave the 6” to 12” of the stem exposed above the soil. Bend it into a vertical position and stake it so that it will grow upright.
Layered red twig dogwood stem tip. Photo Credit: Pat Chadwick
Technique 3 – Compound Layering (also called serpentine layering) – This is a variation of simple layering. Instead of creating just one new plant from a stem, compound layering allows you to create multiple plants by alternately covering and exposing sections along the length of the stem. It’s a particularly good method to use for vines such as clematis and wisteria.
Technique 4 – Mound Layering – This method is a good way to get lots of new plants from one parent plant. It works best for dormant plants that are heavily stemmed with close branching. Candidates for mound layering include lavender, wormwood, spirea, flowering quince, and cotoneaster.
- Prune the dormant stems back to 1 inch above the surface of the soil.
- When shoots begin to emerge in spring, mound soil up over them. Roots will develop at the base of the shoots.
- Separate the new plants from the parent plant by cutting the stems just below the newly developed roots.
Technique 5 – Air Layering – This method of layering is much more involved than the previous four. Instead of rooting new plants in soil, air layering is used to create a new plant on the stem or branch of a plant, hence the name. Air layering is appropriate for hardy shrubs with stems or branches that cannot be bent down to the ground such as azalea, camellia, magnolia, and holly. For best results, choose a stem from the previous season’s growth that is pencil size or slightly larger diameter. Or, if later in summer, choose a mature shoot from the current season’s growth. To air layer a woody plant such as a shrub or tree:
- Choose a spot for layering about a foot or so from the tip of the branch and remove all leaves and twigs from 3” to 4” above and below that point.
- Use a sharp, sterile knife to make two parallel cuts about an inch apart around the stem and through the bark and underlying cambium layer.
- Then make a couple of perpendicular cuts between the two parallel cuts and remove the ring of bark.
- Scrape the bared ring to remove the cambial tissue. This is important to prevent callus tissue from forming.
- Pack a ball of damp (but not soggy) sphagnum moss or coir about the size of a baseball around the cut area.
- Use clear plastic wrap to secure the moss or coir tightly against the wounded area. Seal both the top and bottom so that the packing material doesn’t dry out.
While the emphasis of this article is primarily on landscape plants, air layering is commonly used for propagating houseplants with thick stems such as rubber plant (Ficus elastica) or dumb cane (Dieffenbachia). For more information on the technique, see University of Missouri Extension’s publication on Home Propagation of Houseplants.
HOW LONG DOES IT TAKE TO CREATE A NEW PLANT BY LAYERING?
If there is a downside to layering, it’s that the process requires patience. Some plant species, such as vining plants, may root within a few weeks. Other species, such as some woody shrubs and trees, may need as much as a year to root.
For a stem rooted in late winter or early spring, give it a gentle tug in the fall to see if it is rooted. If it resists being tugged, then the roots are adequately developed, and the plant can be separated from the parent and transplanted elsewhere. If the roots are not adequately rooted, then cover the soil back around the roots and leave the plant in place until the following spring before checking again.
PATENT LAWS REGARDING PLANT PROPAGATION
Before attempting to propagate a plant, check first to see if it is currently under an active patent or has a patent pending. If it is under patent protection, then it is illegal for home gardeners to propagate the plant either by seed or by vegetative methods or to share it with others or sell it. Once a plant patent application is filed with the U.S. Patent Office, the patent is valid for 20 years. But if it is in the public domain, the plant can be legally propagated and shared. This issue pertains more to newer varieties and cultivars than to unpatented older, heirloom varieties.
SUMMARY
Layering is a quick and easy – some might say effortless – way to propagate new plants at no cost. No special tools or gardening skills are required. In fact, the plant does most of the actual work. Of the five layering techniques described, simple layering and tip layering are the easiest. However, it is important to match the technique to the physical characteristics of the plant being propagated.
FEATURED PHOTO: Layered red twig dogwood stem. Photo Credit: Pat Chadwick
SOURCES
Plant Parenting (Halleck, Leslie F., 2019)
Plant Propagation, American Horticultural Society, 1999
Virginia Cooperative Extension Gardener Handbook, Chapter 8, Plant Propagation, page 222.
Plant Propagation by Layering, NC State Extension Publications (ncsu.edu)
How to Propagate Shrubs by Layering, Iowa State University Extension
Propagation by Cuttings, Layering and Division, Virginia Cooperative Extension Publication 426-002
