Layerage

Stems that form root while still attached to the parent plant are called layers, and the practice based on this phenomenon is known as layerage. In some plants artificial methods must be employed, while in others root formation occurs naturally . the rooting medium is usually soil although other materials are used.

Uses:
Layerage is a rather certain method of inducing rooting.Some plants that cannot be started satisfactorily from cuttings can be grown with relative ease from layers, A cutting, having been severed from the plant on which it grew often does not remain alive until roots are formed. A layer, on the contrary, is supported by the parent plant indefinitely and, in the meantime, it is likely to develop rots.


Many plants produce natural layers freely and thus provide a ready source of new plants. This is true of the raspberry and strawberry and certain forms of the blackberry and dewberry. In these plants the layers are produced by either runners or upright canes that, by arching, come in contact with the ground and develop roots. Other plants produce natural layers form the crown of the plant. The quince and chrysanthemum illustrate this behavior.
On a small scale, layerage may be used to good advantage, for the reason that layers don not requirethe close attention as to watering, humidity, and temperature that cutting require Roses are sometimes grown from layers for this reason.
Objections to layerage are that it is a slow and cumbersome method of propagation; that is may interfere with cultivation; and that parents plants produce a limited number of new plants, so that a great number of stock plants must be provided .Despite these disadvantages layerage is used quite commonly in the propagation of some plants, an certainly has wide range of adaptation for the amateur gardener.

Simple Layers :
Branches that have formed roots in one aresa only are called simple layers. Such layers are made by bending the branches to the ground and covering the portion just below the tip with 3 to 6 inches to soil. This practice is usually carried on in early spring, before growth has started. The tip of the shoot is left exposed, to form lwaves and carry on the normal processes of the plant.
It is ac common practice to injure tho portion to be covered, by notching, cutting, girdling, or twisting. This practice destroys the phloem tissue, partially or completely, and retards the downward movement of foood matereals manufactured by the leaves of the exposed terminal potion., The result is an accumulation of plant food above the injured area, and such plant food is favorable to the development of roots by the layer. It is also considred that the injury checks the downward movement of hormones, and the concentration of these in the injured area stimulates Root Formation.
The season of the year for making layers varies with the species.With some the best results are obtained if layers are made in late winter or early spring; with others, late summer and fall seem to be transplanted successfully to a new lactation other require two seasons to develop a strong root system a strong root system.
Many different kinds of plants can be3 grown from simple layers. In actual use, however the method is restricted largely to very difficult species, and to plants grown for home use.
Tip Layers: A tip layer differs from a simple layer in that the tip is completely covered. Tip layers are used extensively in the propagation of some varieties of blackberries, dewberries and raspberries. In starring new plants by this method the tips of branches are placed int he soil, pointing downward, to a depth of 2 to 3 inches, and covered the soil is paced lightly to hold the branch securely in place. For the production of a larger number of plants a shallow furrow many be plowed along the row a short distance form the plants, and all the available lateral tips laid in the furrow and covered. Tip layers of berries are best made in late summer. The covered portion will shortly become etiolated and fleshy. Attentive roots will develop in from 2 to 3 weeks, and the layer can then be dug, severed from the parent plant , and replanted in ta permanent lactation. This can be done shortly after rotting occurs, but best results are obtained by allowing them to remain in place utile the following spring, and replanting at that time. The rooted layer should be replanted with tip pointing upward since the stem will develop from the terminal bud

Compound Layers.
Long shoots that are alternately covered and exposed over their entire length are known as compound layers.They normally form roots at each node where they are covered and develop new shoots from buds at nodes that are not covered . When they have grown one season or more, the several layers are severed so as to provide a root system on the proximal portion of each layer and a top on the distal portion. The time of the year for making and for replanting compound layers is influenced by several factors. Normally they are made in late winter and early spring. The rooted layers may occasionally be replanted later in the same season, but mere commonly they are allowed to grow one or two full seasons in order to develop a strong root system. Compound layerge is adapted to the prorogation of the Muscadine grape. The natural production of rosettes and roots by the strawberry plant at each second node o the runners is similar to compound layerage.

Trench or Continuous Lyares :
The type of layer differs from the compound layer in that the branch is covered for its enter length instead of alternately. This method in adapted to the propagation of own-rooted apple, pear, cherry, and other plants needed for research investigations or Therese . It can also be used on Muscadine and other kinds of grapes that do not root well from cuttings. Essentially, trench layerge consists of placing the main stem of a plant in trench in a way that will permit young stems to develop from later buds and to form roots on the lower portions of these new stems.Plants that produce long vines can easily be bent to the ground.Other like apple and pear, must be planted in horizontal potion with the roots in proper contact with the soil and the main stem in the trench. Obviously, this would be practicable only with small whip like plants. In practice three methods are used in covering continuous layers. By one method, the layer is planed in an open trench. New shoot develop from lateral buds, and when they are about 6 inches high, soil is added to a depth of avout 5 inches. Roots develop on the bases ot the shoot that are covered with soil. By another practice, about 1 inch of fine soil is added when the layer is first placed in the trench. The new shoots push upward through this layer. As the shoots elongate, more soil is added around them until they are covered to a depth of 5 to 6 inches. The bases of shoots that develop when treated in this manner are etiolated, a condition favorable to ready rot formation. By still a third practice, the layer is covered root to a depth of about 3 inches with loose soil when it is made. The shoots push upward through this layer and develop roots from the etiolated portion of the stem below ground.In every case, the roots arise adventitiously from the cambium layer of the new stems. The best
season for making contentious layers is in late winter or early spring. The rooted plants are allowed to develop one full growing season before they are removed from the parent layer and replanted.

Mound or Stool Layers :
This method is especially satisfactory for the rooting of apple and quince rootstock and issue in preference to interlayering when possible, as it involves less trouble and expense. A stock bed is established by setting young plants 3feet apart in rows 4 feet apart. The plants are headed back before growth starts and are allowed to arrow for one season. The following winter the plants are cut back within 3 inches of the ground leave, with the result that many new shoots arise from the base during the following season.In the case of appl;es, which root freely from these new shoots, the stools are allowed to remain uncovered during the early part of the growing season. The greatest number of shoots are produced in this way after they are formed and have reached the height of 8 inches thy re mounded with 5 to 6 inches of soil. Mounding should be done with moist soil, which should be planed from the center outward in order to bend the shoots out and give them better scarping. This spacing seems to give a better rooting especially with vigorous shoots.

When plums are being grown, the procedure is modified and the plants mounded before the new shoots rapper. This practice results in the formation of fewer new shoots than the other method, but the shoots that are produced are etiolated and form roots better than those that are produced before mounding. This applies not only to shoots from stools and layers but also to stems used for cuttings, from which better rooting is obtained when there bases have been etiolated during growth.

After the plants have been mounded by either method in early spring, they are allowed to grow during the rest of the season and roots will form on the new shoots along the covered portions of the stems. In early winter the rooted shoots are removed and planted in the nursery row .These parental set at a depth ao about 6 inches. They will be ready to bud during the summer of the following year, or they may be grafted at the end of one season in the nursery. The chrysanthemum forms natural mound layers from the overwintering crown at the beginning of each new growing season. These develop into new plants when thy are detached and planted out separately. Quince and Japanese flowering quince ave habits of growth that permit them to be propagated from natural layers from the crown of the plants. Varieties of currants and gooseberries that do not grow readily from cuttings are frequently grown from mound layers.

Air Layers.
A method used to root branches of upright growing plants that don not sprout or sucker readily is known as air layerage. Chinese layerage and pot layerge are other names for the same method.The stem is first injured by sliching, notching, rigging , or binding. Care must be exercised not to injure it sufficiently as to cause breadage or death of the layer. This can be effected easily by binding with copper wire wrapped tightly about the stem, and it has the same effect on rooting as the other treatments. It is common practice to apply a coating of one of the concentrated hormone dusts to the area where roots are to from.