The Horticulturist 24: 74-76 (March, 1868)

Propagating Plants
A. S. Fuller

INFLUENCE OF STOCK ON THE GRAFT.

THAT the stock upon which a graft is inserted has an influence upon its future growth, is well known. If it were not so, then grafting, budding, and similar modes of propagating plants would not have been discovered, nor the beneficial results of these operations been enjoyed by mankind. But merely supporting the graft or furnishing it with the required amount of sustenance, does not convey the full meaning of the term influence as generally understood in connection with this subject.

The stock not only acts as a medium through which the graft obtains sustenance from the earth, but it in a great measure imparts its own characteristics to it; and it is thus we change the giant into a dwarf, the slow growing plant into a rapid, and many other variations from the natural habits of plants, simply through the influence of the stock on the graft.

We may not be able in every instance to determine the true cause of certain variations which may appear to be antagonistic with what we call natural laws, still, for all practical purposes, our knowledge of this subject is sufficient to enable us in many instances to so change natural products that their value to us is increased many, many fold.

The common method of producing dwarf trees is one of the most familiar instances of the influence of the stock on the graft. But there is, however, a too general inclination on the part of the public to misapply the term dwarf, as many suppose that it is nearly, if not quite, synonymous with debility or stunted growth. This idea is an erroneous conclusion, for in many instances what are called dwarf trees are equal to and often more vigorous than standards. For instance, we will select two seedling stocks, one shall be the Mahaleb Cherry and the other the Mazzard; both shall be of the same size and of equal vigor. Upon these we will insert buds of the May Duke Cherry, or any other variety. Now, the chances are in favor of the bud on the Mahaleb stock making the most rapid growth for the first one or two years, and still the Mahaleb is considered to be one of the best stocks on which to dwarf the cherry. Now, the Mahaleb stock does not lessen the vigor of the tree, but merely imparts to the graft its peculiar habit of growing and spreading, and we are obliged to allow and assist the tree to grow in this form, or it will surely become feeble and perish. The bud inserted upon the Mazzard stock will shoot up into a tree, assuming its natural form, but the influence of the stock will be to make it grow pyramidal and quite tall, because that is the natural habit of the Mazzard Cherry.

From my own experience, I conclude the same rule holds good with many other dwarf stocks, and I have, as a general thing, secured a larger growth of the pear for the first two or three years, and even longer with proper care, on the quince than upon the pear stock. The influence of these stocks is shown by imparting their peculiar form of growth to the graft, early fruiting, etc., more than checking their vigor. By these remarks, we wish to be understood as only referring to stocks upon which the graft readily unites. If we undertake to trim up our dwarf trees and make standards of them, we soon discover our mistake; and I once knew of an instance where ten thousand cherry-trees on Mahaleb stocks were destroyed in endeavoring to change them from dwarfs into standards. In this instance, the first sign of failure appeared upon the upper portion of the stem and among the branches in the form of a species of fungus or blight, which killed the upper portion of the tree, and at the same time young, vigorous branches were produced in abundance on the lower portion of the stem; and thus the tree assumed its natural low growing or dwarfish habit.

In some instances, we use stocks merely as a temporary support to the graft, not expecting that a permanent union will be formed, as in grafting the tree paeonia upon the herbaceous, or the stem of one dahlia upon the tubers of another. But with trees we usually expect permanency, and therefore select stocks that shall not only support the graft, but develop those particular characteristics which are most desired.

The chief point of influence of the stock on the graft may be stated as follows: 1st. The stock gathers the crude materials for the support of the graft from the soil, and in doing so it may furnish it in such quantities as to produce rapid growth, or the reverse.

2d. Its tendency is to impart its own habit of growth to the graft. Early or late maturity and productiveness being characteristics of different varieties, the stock will therefore hasten or delay fruiting.

3d. One species of stock will extract from the soil the peculiar ingredients which are necessary to support the graft, while another will not, consequently a variety of species of fruit may fail upon one stock and succeed upon another in the same soil and locality.

4th. The hardiness of a tree is but slightly changed by the stock, except as its growth is influenced, to mature early or late in the season.

5th. The quality of the fruit is occasionally influenced by the stock; but the true cause of this is not yet sufficiently understood to allow of positive rules being given by which it may be avoided. Size of the fruit is also considerably changed by the use of different stocks. I know of two Bartlett pear-trees of the same age and standing side by side, and both apparently of equal vigor, still for ten years one has produced very large fruit and the other small. The number of specimens upon each tree being reduced to an equal number, the difference in size was still the same. With such examples before us we can not but conclude that the stock in some instances does exert sufficient influence to change the size of the fruit.

6th. The stock will not only impart vigor to the grafts, but will also transmit diseases. It is therefore just as important to avoid the one as to endeavor to secure the other.

INFLUENCE OF GRAFT ON STOCK.

The influence of the graft on the stock is seldom referred to in our horticultural works.

Downing says: "The influence of the graft on the stock seems scarcely to extend beyond the power of communicating disease." But if we have discovered this much, it proves that there is an influence, and if it is sufficiently potent to "communicate disease," then it should also be powerful enough to impart other characteristics as well. Mr. J. J. Thomas, in his "American Fruit Culturist," edition of 1849, makes a few remarks upon this point, which I think are worthy of notice. He says: "The extension of the wood of the stock by successive depositions from the leaves of the graft and through the cellular system of the bark, so as to preserve the strict specific identity of the wood of the former, is familiar to every practical cultivator. The same seedling cherry stocks, grafted with sorts of different degrees of vigor, soon vary in amount and size of the fibrous roots. Trees of the Imperial Gage and Jefferson Plum, a few feet in height, when budded on the wild plum, were found to have only half the amount of roots possessed by the unbudded stock of the same age."

Every nurseryman must have observed that some varieties of the pear have far more fibrous roots than others. So marked is the difference, that the common laborers in the nursery soon learn to distinguish them, and will proceed quite differently in digging the trees of each variety, knowing that one has few long, naked roots, while others have short and numerous fibrous ones. These various forms of roots can not be satisfactorily accounted for in any other way but to ascribe the cause to the influence of the graft. If we take a seedling apple-tree of one or two years old and divide the root into two sections, upon one of which we insert a cion of the Newtown Pippin and on the other one of the Northern Spy, and then plant them both in exactly the same soil and cultivate alike, when, after three or four years, we dig them up, the roots will have a decidedly different appearance. Still, with all the influence which the cion has had upon the roots, changing their appearance and form of growth, if cuttings are taken from these roots and allowed to grow up into trees and bear fruit, they will produce the same sort in both instances. The vigorous growth of root depends as much upon the stems and branches as the latter does upon the root. If we graft a weak-growing variety upon a strong, vigorous one, there is no certainty that the stock will be able to overpower the inherent feebleness of the cion and keep it growing vigorously for any considerable length of time. The cause of this, in many instances, is probably owing to the fact, that the leaves on the graft are not capable of assimilating the sap as rapidly as is requisite for the health and growth of the entire plant. Roots gather the crude materials which make up the bulk of the plant from the soil, but they can not grow unless the leaves return to them the requisite materials for their extension. Now, if the leaves are not capable of assimilating all the materials that the roots have the power of absorbing from the soil, it must be apparent that there will be at least a partial check to the circulation of sap, consequently a diminution of growth. A few years since I had an opportunity of witnessing a singular effect of leaves on growth. An old Easter Beurre pear had been allowed to over bear, and, consequently, had become very much enfeebled in growth, so much so that it did not make an inch of growth upon any one of its branches. One of the small branches was cut off and a cion from a Vicar of Winkfield placed upon it. The graft made a growth of two feet the first season; the next season the graft not only continued its rapid growth, but the entire tree appeared to revive and send out new and vigorous shoots. My theory in this case may not be a correct one, but I believe that the cause of this change in the old tree was owing to the demand which the new graft made upon the roots for plant-food; they, in return, received materials for their extension. The supply which was gathered and sent forward not being all absorbed by the graft, was forced into the old branches, increasing the size of their leaves, thereby causing a reaction in the entire tree. Healthy leaves indicate healthy growth, and new leaves cause the production of new roots, and these in return furnish the materials for continued growth, and thus a reciprocal action is constantly going on between root and branches.


PEACH ON PLUM.—Wherever the peach does not succeed well, planted upon its roots, because of the soil being too stiff, clayey, or wet, it will be found that if the peach be budded on the plum it will thrive well, and give good crops of fruit, and, at the same time, give to the tree more hardihood to endure extreme changes of temperature.