Plant Propagation Technique
Layering is a method of propagation in which roots are caused or assisted to form on stems that are still a part of the parent plant. After the roots have formed, the section of the stem bearing them is severed from the original plant and planted as a separate individual. In all cases of layering, the parent plant supplies the food until the new plant has an adequate root system and can survive on its own. So as to ensure this continuous food supply, layering outdoors is best done in spring.
Simple layering is accomplished by bending and covering branches (except the tip, which must be kept uncovered to maintain circulation) with soil and holding them in place with pegs or stones until rooted. In a modified form of this method, the stems are laid in shallow trenches prior to anchoring or pegging. The branches are often twisted, scraped, cut, or otherwise slightly wounded on the underside at the points where rooting is desired to encourage the quick formation of roots.
Compound layering, also known as serpentine layering, consists of bending flexible stems in a series of curves along the ground so that the “down” sections or “troughs” are in contact with and covered by soil and the “up” parts or “crests” are exposed. Otherwise, this method is the same as simple layering.
Continuous layering works by burying whole branches, except the tips, of plants that readily produce roots.
Modified Continuous Layering
Modified continuous layering is popular for the propagation of certain grape varieties and other vines whose cuttings root poorly. In spring, canes of the previous year’s growth are pegged down in shallow, open trenches. When shoots several inches long have developed along these canes, the latter are wounded on the underside of the points where the shoots are, and soil is piled on these points and around the base of the shoots. After roots have formed the canes are cut between the rooted shoots, which are transplanted and carried on as separate plants.
Mound, Hillock, or Stool Layering
Mound, hillock, or stool layering is accomplished by cutting bushes such as blueberry back to within a few inches of the ground in spring and heaping earth over the stumps. These send up shoots that develop roots in the mound of earth. The following spring the rooted shoots are broken apart and planted in nursery rows or their permanent position. Mound layering is occasionally used to root rhododendrons.
Chinese, Pot, Aerial, or Air Layering
Chinese, pot, aerial or air layering is a greenhouse or home practice employed chiefly on stiff, erect-growing plants, such as dracaena, croton, oleander and rubber plants, which have become “leggy” and unsightly. The stem is wounded at the point where roots are wanted on the leafy top of the plant, generally by girdling or notching, a pebble or chip being inserted in the cut to keep it open. The wounded place is then bound with soil, sphagnum moss or other moisture-retaining material held in place by a bandage of burlap or cloth, or a special type of layering pot, and kept moist until roots have formed and penetrated the material. The entire top of the plant is then cut off just below the new roots and planted as a new plant.