Layering Plants for Propagating New Plants in Your Garden
Methods for Layering Plants
Layering plants is perhaps the most simple and useful form of increasing stock and therefore propagating plants, in the ordinary garden but, even with this method, techniques have been evolved for virtually all types of plants. There are some 15 recognised techniques:
1. Simple bending
2. Tonguing and heeling
9. Growing point layering
See this article about air layering roses. The basic principles apply for any plant you wish to propagate by the air layering method.
The common advantage of all of these techniques is that the portion to be rooted is not at risk - in that the portion, be it branch or tip, is not severed from the parent plant until it has made roots and is capable of supporting itself. This is particularly useful where cutting material is scarce or a subject takes a long time or is difficult to root for then the cuttings would be at risk. Furthermore, older material may be used which would not readily root if inserted as a cutting.
Personally, I know of no upper limit to the age and thickness at which certain subjects would fail to root by layering. I have seen trees getting on for 100 years old which have been successfully layered and cases can be frequently seen of apple trees and laburnums which have fallen down and have re-rooted along their stems. Certainly, this is the safest method of propagating for the not-so-skilled, or where facilities are not available, for it prevents many disappointments.
All the techniques are based on the principle of the partial arrest and disturbance of the sap passing along the stem at a point where roots are to be formed. Of course, in some plants roots will form at any point and all that is required is to cover them with a suitable rooting medium, but very often special techniques must be used to satisfy particular conditions. This takes the form of arresting the flow of sap and, incidentally, there are conflicting opinions as to why checking the sap should encourage rooting but the fact remains that in practice, if the bark and the layers beneath the bark are constricted either by wire, scraping, cutting, nicking or some other form of strangulation or fracture, sooner or later roots will form. The object, of course, is to induce these roots to form on the portion which is to be removed.
A simple method of layering plants is to take a branch or portion of the plant situated in a suitable position so that it can be bent down in order that a portion of the stem enters the ground. The piece actually buried must be roughened, nicked or slit and preferably bent up at as near a right angle as possible and secured to a stake. This bending further constricts the flow of sap. A hollow should be taken out of the soil and replaced with a mixture of peat and sand so that the bent or lacerated portion sits on this. Then it, in turn, is covered with more of the mixture and the soil replaced and firmed down.
Subjects such as holly or rhododendrons may take a long time to root, so an easy way is to place a brick or flat stone on the portion to be rooted. This not only holds the branch in position but keeps the soil beneath the brick or stone cool and moist.
Layering plants, although actually simple in operation to perform, is an immensely complicated process so far as root production is concerned, but for the operator it is enough to say that this is an almost 100 per cent sure way of ensuring vegetative reproduction of the plant in question. Advantage can often be taken of this natural stem rooting when it is desired to increase the size of a clump, even without actually severing the rooted portion after it has rooted.
With the serpentine form of layering, this may be done with a long flexible branch so that a number of layers can be obtained at every point where the stem touches the ground.
Tip layering is most useful for propagating blackberries, loganberries and rambler roses. In this case, if the young, actively growing tip, is pegged securely to the ground it will root quickly and readily.
Layering Plants - Different Methods
Layering a rhododendron
Layering a rhododendron using the tongue and heel method involves bending down a branch and slitting it partially through. This is bent back so the slit opens and is held down in the soil by means of a piece of bent wire. As rhododendrons take time to root, the branch is held in position by a stone or brick. The end of the layered branch, supported by a stake, will eventually form a new plant that can be severed from its parent when a root system has been established.