Layering is another simple form of propagation that can be done at home without special equipment. Layering is a natural form of propagation that often takes place inadvertently. Layering usually is most effective with deciduous shrubs. However, I have seen broad leaf evergreens such as Rhododendrons, and Piers Japonica propagate themselves through inadvertent layering.
Inadvertent layering is something that happens both in the natural environment of woods, or in a commercial nursery. In the woods, the lower branches of a plant get pulled to the ground from their own weight, or because of snow sticking to or laying on the branches. As the branches lay on the ground, all of the necessary conditions exist for the plant to develop roots at the point where the branch is resting on the ground.
In a commercial nursery, many shrubs are planted in rows. The rows are cultivated on a regular basis to keep weed growth to a minimum. Through the cultivation process, a few branches can be inadvertently but partially covered with soil. When this happens the plants often develop roots at the point that they were covered with soil.
At home, you can intentionally layer a plant. All you do is dig a small hole near the base of the shrub, pull down one of the lower branches, bending it in a U, and force the bottom of the U in the hole leaving the end of the branch sticking up out of the ground. Fill the hole with soil covering the branch. The portion of the stem that is covered with soil will develop roots.
Making a small wound on the portion of the stem that is to be buried will help to stimulate root development. To make this wound, using a knife, simply make an angled cut into the stem. Make the cut about 1/2″ long, cutting into the stem not quite half way. As you bend the stem to force it into the hole, be careful not to break the stem at the cut. You can also wound the stem by simply scraping off about 1/2″ of bark with a knife.
It is also beneficial to treat the wounded area with a powder root inducing compound, available at most garden centers.
Some branches are more rigid than others. It may be necessary to anchor the branch down using a piece of heavy wire bent in a U, or a fork-shaped branch. Or you can hold the branch down by placing some form of weight on the soil covering the branch.
Layering is a propagation technique that can be done in the fall or spring. You should achieve great success with layering as late as the middle of May. Layering yields great success on many deciduous shrubs because you are not actually removing the branch from the plant at the time of the layering process. The new plant that you are attempting to propagate is still attached to, and being nurtured by the parent plant throughout the entire process.
Even though layering can be done until mid May, I would suggest that you do your layering as early as possible in the spring to give the plant ample time to establish an extensive root system.
If you layer a plant in the fall, you should not attempt to remove that layer from the parent plant until the following fall or spring. Do not disturb the layer while the plant is actively growing, wait until the plant is dormant.
If you layer a plant in the spring, you might be able to remove it from the parent in the fall after the growing season has ended, but I would leave it alone until spring. If you have a mild winter and the soil temperatures are fairly warm, further root development might take place over the winter months.
Liners planted out in the fall can often be forced out of the ground by the freezing and thawing process. (Small plants are often called “liners”, short for lining out stock.) That’s why I prefer to do most of my planting of small plants in the spring.
Since the invention of intermittent misting equipment, not very many commercial nurseries use layering as a means of propagation. It is too labor intensive for the number of new layers a nursery can obtain. It also ties up valuable field space that could be used for more productive things.
Keep in mind that wholesale nurseries produce plants by the tens of thousands. Nurseries have to keep a whole block of ‘stock’ plants that are to be used for nothing but layering. A good stock plant might yield 30 or 40 layers, whereas the same ‘stock’ plant could yield several hundred softwood cuttings. Understanding how commercial nurserymen do layering will help you achieve better results at home.
Most deciduous shrubs have the ability to put on 18-36″ of new growth each year. This new growth is the ideal wood for layering. If you prune the shrub heavily the year before you intend to use it for layering, it will produce a substantial amount of new growth that will be ideal for the layering process.
I would actually cut the shrub to within six or seven inches from the ground. This will force the shrub to put out many new branches the following growing season. In the fall of the same season, this new growth would still be fairly pliable and could be easily pulled to the ground to be layered.
Once these new layers are rooted they can be removed by cutting the branch just below where the new roots have developed. At the same time, the parent plant should be cut back just like before, and it will produce more new growth for the next layering season.
Want to learn more about propagation by layering? Take a look at Plant Propagation Techniques at PlantPropagation.org