Propagation by Means of Budding and Grafting
taken from The Nursery Manual (1934) by Liberty Hyde Bailey
The vegetative parts of plants may be severed and inserted in earth or water for the making of new plants. Under certain conditions, severed parts may be inserted in other plants with the intention of making new plants: this process is known broadly as grafting. The part removed from the parent and inserted in the foster parent is the cion (or scion). If the cion is only a bud with a bit of bark and wood attached, the operation of inserting it is usually spoken of as budding, and the term grafting is restricted to the use of a cion consisting of a piece of twig bearing two or more buds; yet the operation is all grafting, independently of the make of the cion. Budding is really only one of the forms of grafting. What is known as the graft is the completed work, — the cion set in its new plant; but sometimes the word graft is used in the sense of cion. The plant or part in which the cion is set is the stock. The whole subject of grafting, comprising the knowledge and discussion that goes with it, is known as graftage. While all plants can probably be grafted, in practice the operation is confined mostly to trees and shrubs.
1. GRAFTAGE IN GENERAL
The reasons for grafting are two: (1) To keep or perpetuate a variety true to name, which is not accomplished by seed propagation. Thus, if one would grow the Elberta peach one would not attempt it by planting the seed of Elberta; on any seedling peach-stock buds from the Elberta could be set and the resulting tree would be Elberta. (2) To multiply the plant, by making many plants from one. Usually both purposes are accomplished at the same time. To these reasons may be added a third: to produce a given change in cion or stock, as when a variety is dwarfed by working it on a slower-growing stock, or fruit-bearing is hastened by setting a cion in an old stock; weeping varieties are grafted high on straight bodies, and low-growing things are elevated on long trunks as in Fig. 127 (Beal, Cornell Reading-Course Lesson). While the budding of roses far above ground is allowable for the making of “standards,” care should be taken in ordinary propagation to have the bud close to the surface, as illustrated by Beal at the right in Fig. 128.
Graftage is always a secondary operation. That is, the root or stock must first be grown from seeds, layers or cuttings, and this stock is then grafted or budded to the desired variety. Graftage is employed in the propagation of the tree-fruits in America, and of very many ornamental trees and shrubs, and it is indispensable to the nursery business.
In some species, which present no marked or named varieties, propagation by seeds or cuttings is for various reasons so difficult or uncertain that recourse must be had to graftage, quite independently of the perpetuation of particular horticultural varieties. This is true in many of the firs and spruces, which do not produce seeds to any extent in cultivation. In other cases, graftage is employed to aid the healing of wounds or to repair and fill broken tops. It has been used to make infertile plants fertile, by grafting in the missing sex in dioecious trees, or a variety with more potent pollen as practiced in some of the native plums.
The old discussion as to whether grafting is a devitalizing process is quite aside from the question, seeing the many necessities that must be met. Poor work and the matching of uncongenial kinds are surely to be avoided, but it is now too late to raise the question in the abstract.
Grafting is not unknown in nature. Often limbs of trees grow together solidly when they cross. Fig. 129 (left) shows a natural graft of two trunks which in some way became entangled. Fig. 129 (right) is a similar case, but here the four trunks were tied together intentionally and are now grown into a firm union. In these cases the trees are of the same kind or species.
The limit within which graftage is possible or desirable between species, is determined only by experience. Probably all exogenous plants – those with a distinct bark and pith – can be regularly grafted. Plants must be more or less closely related to allow of successful graftage of the one on the other. As a rule, plants of close botanical relationship, especially those of the same genus, intergraft with more or less ease; yet this relationship is by no means a safe guide, particularly as the current fashion among taxonomists of splitting up genera into fragments obscures affinities. A plant will often thrive better on a species reputed to be of another genus than on a congener. The pear, for example, does better on many thorns than on the apple. Sometimes plants of very distinct genera unite readily. Thus among cacti, the leafless zygocactus (usually known as epiphyllum) grows well on the leaf-bearing pereskia. It should be borne in mind that union of tissues is not a proof of affinity. Real affinity can be measured only by the thrift, healthfulness and longevity of the cion. The bean has been known to make a union with the chrysanthemum, but it almost immediately died. Soft tissues,· in particular, often combine in plants that possess no affinity whatever, as we commonly understand the term. Neither does affinity refer to relative sizes or rates of growth of stock and cion, although the term is sometimes used in this sense. It cannot be said that some varieties of pear lack affinity for the quince, and yet the pear cion grows much larger than the stock. In fact, it is just this difference in size and rate of growth that constitutes the value of the quince root for dwarfing the pear. When there is a marked difference in rate of growth between the stock and cion, an enlargement will occur in the course of time, either above or below the union. If this occurs on the stem, it makes an unsightly tree. If the cion greatly outgrows the stock, a weak tree is the result.
The inter-relationships of stock and cion and the physiological reactions in grafting have been made the subject of prolonged study by the Frenchman, L. Daniel. In this field we are to expect important applications to nursery practice in the course of time.
The mutual influence of cion and stock is a subject of perpetual fascination. It has been much discussed, but without real conclusions or much influence on practical operations outside such matters as the operations of dwarfing and the elevation of weeping heads on straight stocks. Some of the real and supposed reciprocal influences may be mentioned: graftage may modify the stature of a plant (dwarfing and vice versa); adapt plants to adverse soils and climates; correct a poor habit; afford good trunks for weeping and drooping plants; hasten and sometimes augment fruitbearing; modify the season of flowering or ripening; increase the size and modify the quality of flowers and fruits; transmit disease.
Classification of graftage
There are three general divisions or kinds of graftage, between which, however, there are no decisive lines of separation: 1. Bud-grafting, or budding, in which a single bud is inserted under the bark on the surface of the wood of the stock. 2. Cion-grafting, or grafting proper, in which a detached twig, bearing one or more buds, is inserted into or on the stock. 3. Inarching, or grafting by approach, in which the cion remains attached to the parent plant until union takes place. This last is so much like grafting proper, and is so little used, that it is discussed under the head of grafting in the succeeding parts of this chapter; it is essentially a mode of layering. Each of these divisions can be almost endlessly varied and subdivided, but in this discussion only the leading practices can be detailed. The following enumeration, after Baltet, gives a fair idea of the kinds of grafting with distinct names:
- Bud-grafting, or budding
- Grafting with shield-buds.
- Bud-grafting under the bark, or by inoculation.
- Bud-grafting, ordinary method.
- Bud-grafting with a cross-shaped incision.
- Bud-grafting with the incision reversed.
- Bud-grafting by veneering.
- Bud-grafting, the combined or double method.
- Flute-grafting, common method.
- Flute-grafting with strips of bark.
- Grafting with shield-buds.
- Cion-grafting, or grafting proper
- Side-grafting under the bark.
- Side-grafting with a simple branch.
- Side-grafting with a heeled branch.
- Side-grafting in the alburnum.
- Side-grafting with a straight cleft.
- Side-grafting with an oblique cleft.
- Ordinary method.
- Improved method.
- Grafting de precision.
- Veneering, common method.
- Veneering, in crown-grafting.
- Veneering with strips of bark.
- Crown-grafting by inlaying.
- Side-grafting by inlaying.
- Cleft-grafting, common single.
- Cleft-grafting, common double.
- Cleft-grafting, oblique.
- Cleft-grafting, terminal.
- Cleft-grafting, terminal woody.
- Cleft-grafting, terminal herbaceous.
- Whip-grafting, simple.
- Whip-grafting, complex.
- Mixed grafting.
- Grafting with cuttings.
- When the cion is a cutting.
- When the stock is a cutting.
- When both are cuttings.
- Root-grafting of a plant on its own root.
- Root-grafting of a plant on the roots of another plant.
- Grafting with fruit-buds.
- Side-grafting under the bark.
- Inarching, or grafting by approach
- Method by veneering.
- Method by inlaying.
- English method.
- Inarching with an eye.
- Inarching with a branch.
- Method by veneering.
Times and methods
Grafting of one kind or another can be performed at almost any time of year, but the method must be varied to suit the season and other conditions. The one essential point is to make sure that the cambium layers, lying between the bark and hardwood, meet as nearly as possible in cion and stock. This cambium is always present in live parts, forming woody substance from its inner surface and bark from its outer surface. In the season of greatest growth it usually occurs as a soft mucilaginous and more or less unorganized substance, and in this stage it most readily repairs and unites wounded surfaces; and for this reason the grafting and budding of old trees are usually performed in the spring. Later in the season, the cambium becomes firmer and more differentiated, and union of woody parts is more uncertain.
It is necessary to cover the wounds to check evaporation from the tissues. In outdoor work, wax is commonly used for all kinds of grafting that wound the wood itself, but in budding, the loosened bark, bound down securely by a bandage, affords sufficient protection. It is commonly supposed that an ordinary cleft-graft cannot live if the bark of the stock immediately adjoining it is seriously wounded, but the bark really serves little purpose beyond protection of the tissues beneath. A cion will grow when the bark is mostly removed from the stub, if adequate protection is given which will not interfere with the formation of new bark.
The cion must always bear at least one good bud. In most cases, only buds that are mature or nearly so are used, but in the grafting of herbs very young buds may be employed.
These simple requirements may be met in an almost innumerable variety of ways. The cion or bud may be inserted in the root, crown, trunk or any of the branches; it may be set simply under the bark, or inserted into the wood itself in almost any fashion; and the operation may be performed either on growing or dormant plants at any season. But in practice there are comparatively few methods sufficiently simple and expeditious to admit of general use; the operator must be able to choose the particular method best adapted to the case in hand.