Root-grafting, especially of fruit-stocks, is performed almost entirely by the whip-graft. This operation is performed in winter. The stocks, either one or two years old, are dug and stored in the fall. In January or February the grafting is begun. In true root-grafting, only pieces of roots are used, but some prefer to use the whole root and graft at the crown. In piece-root-grafting, from two to four trees are made from a single root. A piece of root from two to four inches long is used, as shown in [Fig. 71]. The parts are usually held by winding with waxed string or waxed bands. The string should be strong enough to hold the parts securely and yet weak enough to be broken without hurting the hands. No. 18 knitting cotton answers this purpose admirably. It should be bought in balls, which are allowed to stand for a few minutes in melted wax. The wax soon saturates the ball. Waxed bands are made by spreading melted wax over thin muslin, which is cut into narrow strips when dry. The string is the more useful for rapid work. The grafts are packed away in sand, moss or sawdust in a cool cellar until spring, when the two parts will be firmly callused together. Some propagators are now discarding all tying of root-grafts. The grafts are packed away snugly, and if the storage cellar is cool—not above 40°—they will knit together so that they can be planted without danger of breaking apart. If the cellar is warm the grafts will start into growth and be lost.
Cions are cut in fall or winter, or any time before the buds swell in spring. Only the previous year’s growth is used in all ordinary cases, but in maples and some other trees older wood may be used. In the grafting of peaches—which is very rarely done—the best cions are supposed to be those which bear a small portion of two-year-old at the lower end. This portion of old wood probably serves no other purpose than a mechanical one, as the recent wood is soft and pithy. It is a common opinion that cions are worthless if cut during freezing weather, but this is unfounded. The cions are stored in sand, moss or sawdust in a cool cellar, or they may be buried in a sandy place. Or sometimes, when a few are wanted for top-grafting, they are thrust into the ground beside the tree into which they are to be set the following spring. Only well-formed and mature buds should be used. Sometimes flower-buds are inserted for the purpose of fruiting a new or rare variety the following year.
Fig. 71. Root-graft.
In common root-grafting in the east and south, the cion bears about three buds, and the root is about the same length, or perhaps shorter. The variable and unknown character of these roots as regards hardiness, renders it important in very severe climates that roots should be obtained from the same plant as the cion, the hardiness of which is known. It is, therefore, the practice in the prairie countries to use a very long cion—eight inches to a foot—and to set it in the ground to the top bud. The piece of root serves as a temporary support, and roots are emitted along the cion. When the tree is ready for sale the old piece of root is often removed, or sometimes it falls away of itself. In this manner own-rooted trees are obtained, and it is for this reason that root-grafting is more universally practiced west of the Great Lakes than budding. Even cions of ordinary length often emit roots, as seen in [Fig. 72], but the cions are not long enough to reach into uniformly moist soil. Some varieties of fruit-trees are found in practice to root more readily than others.
There is much discussion as to the relative merits of budding and root-grafting fruit-stocks, but the observations are usually so indefinite or irrelevant that safe conclusions cannot be drawn from them. We have seen that root-grafting serves an indispensable purpose in the cold prairie regions by enabling nurserymen to secure own-rooted trees of known hardiness. Aside from this it may be said that root-grafting is cheaper than budding, as it is performed when labor is cheap and two or more trees are made from one stock, Budded or crown-grafted trees possess a greater root and usually make a stronger growth, at least the first year or two, and it has been said that their roots are more numerous and more symmetrically disposed. But there is not yet a sufficient knowledge of the subject in all its details to allow of dogmatic expressions upon it.
Saddle-Grafting.—Saddle-grafting is a simple and useful method for the shoots of small, growing plants. The stock is cut to a wedge-shaped end by two cuts, and the cion is split and set upon the wedge ([Fig. 73]). The union is then tied and waxed in the same way as exposed whip-grafts. It is oftenest employed when a terminal bud is used, as the wood in such cions is usually too weak to work well with a tongue.