The stock and scion have already been considered. How is coadaptation best obtained? One of the best methods, one that can be used in all seasons and in most conditions of stock and scion, is the side graft, the one that Mr. Jones uses in his nursery work. That is the best argument for this graft. It is, perhaps, the simplest, and at the same time one of the most difficult, of all grafts. The scion is cut wedge shaped and pushed into a slanting incision in the side of the stock. Mr. Jones's modified cleft graft is only a side graft made in the top of the stock after cutting it off. The difficulty lies chiefly in cutting the scion and the incision in the stock so that the fit will be perfectly true. This requires practice.
The bark slot graft, as Dr. Morris calls it, I have used for several years. It can be used only during the growing season when the bark will slip. It is very successful, whether put in at the top of a cut off stock, or inserted in the side of a limb or the trunk. It is not convenient to use unless the scion is considerably smaller than the stock. The scion is cut with a scarf, or bevel, on one side only. When the slot is to be made in the top of a cut off stock two vertical cuts are made through the bark, as far apart as the scion is wide, the tongue of bark thus formed is raised slightly at the top, and the point of the scion is inserted, cut surface toward the center of the tree, and pushed down firmly into place. The superfluous part of the tongue of bark is then cut off. By slightly undercutting the edges of the slot, and slightly tapering it toward the bottom, the scion may be wedged, or dovetailed, in place so as to be very firm. It is even possible to dispense with tying, sometimes, but better not to do so.
When the slot is to be made in the side of a limb or trunk the same procedure is followed except that it is necessary before making the slot to remove a notch of bark, at right angles to the axis of the trunk, so as to free the upper end of the tongue of bark.
The bark slot graft is the easiest of all and readily mastered once the grafter learns to shape a true scion. It is much better than the old bark graft where the bark of the stock is forced away from the wood leaving considerable space to be filled or covered.
These two forms of graft, the side graft, of which Mr. Jones's modified cleft graft is only a variation, as before stated, and the bark slot, in its two variations as described, will meet all needs in topworking hickory trees.
Finally, prevention of desiccation of the graft is obtained by waxing. I have found Dr. Morris's method with melted paraffine satisfactory. The addition of raw pine gum, as advocated by Dr. Morris is undoubtedly an advantage under certain conditions, described by him, but I have not yet used it. The melted parowax is applied to the whole graft and wrapping, leaving no cut surface exposed and the whole scion being covered. If the paraffine is at just the right temperature it will spread at a touch, covering the surfaces without danger of scalding. It is much more effective thus applied than if colder and daubed on. The thicker the waxing the more likely to crack and separate. If the paraffine smokes it is too hot. If it does not smoke, and is dexterously applied, I think we can feel safely that it cannot be too hot. But if applied with a heavy hand it may be too hot even at a temperature so low that it will not spread.
Season for Grafting
According to Dr. Morris nut trees can be grafted successfully in any month of the year. But practically I think that grafting will be limited to that part of the year during which the cambium layer of the stock is active. At other times of the year preservation of the vitality of the scion will be too problematical, it seems to me, even if it is very carefully waxed. However, I may be mistaken. At any rate grafting is not very pleasant work out of doors in very cold weather. The success of bench grafting would be an argument for the success of dormant season grafting out of doors.
After Care
Without thoughtful after care the labor of topworking will almost certainly be lost. There are many ways in which the grafts can be lost but the two commonest are by being choked, or inhibited, by growth from the stock, and by being blown out by the wind. All new growth from the stock must be rigorously prevented. Grafts often make so heavy a growth that, if not blown out by the wind, they will be dragged out by their own weight. Consequently they must often be supported. When the grafts are in, or near, the trunk of the stock, and not too high, the handiest method of support is to cut a sapling of proper length, sharpen the butt, stick this into the ground at the base of the stock, and tie it in two places to the stock. When the grafts are too far out or too high for this method laths or slats or sticks may be tied or nailed to the branches. Support is likely to be even more necessary in the second season when the growth is often astonishing.