"I put the hickory stocks in pots in the spring, and graft them the following spring, say in April, and in the house. The cions are cut during the winter, so as to keep them in good order until wanted for use. I find it is better to operate in April than earlier in the winter. I also graft them out of doors about the beginning of May, when the stocks are growing. They will succeed very well out of doors, provided the stocks are large enough for the cions. Any kind of grafting will do, but crown grafting is the best. I have not done much of late in the way of grafting hickories in the nursery, not having suitable stocks; besides, when the weather becomes warm enough for outside work, vegetation pushes far too rapidly to give a man a chance to do much of this kind of grafting."
Since the above was written and while these pages were being put in type, Mr. Jackson Dawson, of the Arnold Arboretum, Jamaica Plain, Mass., has given his method of grafting the hickories, in Garden and Forest, Feb. 19, 1896, as follows:
"My method," writes Mr. Dawson, "has been to side-graft, using a cion with part of the second year's wood attached, binding it firmly and covering it with damp sphagnum until the union has been made. The best time I have found for the operation under glass has been during February, and the plants have been kept under glass until midsummer, and wintered the first year in a cold frame. In all the genera I find certain species which may be called free stocks,—that is, stocks which take grafts more readily than others. Thus, nearly all the oaks will graft readily on Quercus Robur; the birches will graft more easily on Betula alba than on others; so of the hickories, observation has led me to believe that the best stock is the bitternut, Hicoria minima. This species grows almost twice as rapidly as the common shagbark hickory, and while young the cambium is quite soft. I should advise anyone who wishes to propagate hickories on a large scale to grow stocks of this species in boxes not more than four inches deep. In this way all the roots can be saved and there will be no extreme taproot, and when shaken out of the boxes the plants are easily established in pots and ready for grafting. If taken up in the ordinary way from the woods, it requires almost two years to get them well rooted, and often the stocks die for want of roots after the grafts have really taken. If grown in rich soil, the stocks will be large enough to use in one or two years. I should then pot them early in the fall, keeping them from heavy frosts, and bringing them into the house about the first of January, and as soon as they begin to make roots. I should side-graft them close to the collar and plunge them in sphagnum moss, leaving the top bud of the graft out to the air. The graft ought to be well united about the last of March, when the plants should be taken from the sphagnum and set in the body of the house to finish their growth."
All who have had any experience in the propagation of trees by grafting in spring, are well aware of the flight of time, in the hurry of work that must be done in a few days or not at all. It is true that the season for grafting may be prolonged or extended a little by cutting the cions in winter and storing them in a cool, moist place, where they remain dormant after vegetation has started in the open air; but this does not affect the stocks, and these may come on slowly or rapidly, varying with the seasons, and the grafter must not only watch for opportune moments, but take his chances of striking the right time and conditions, in order to be successful. With such hard wood trees as the hickories it is better to be a little ahead of time than a few days too late, for frosts, and even quite a severe freeze, will not injure a dormant cion, and under the most favorable conditions the union between stock and cion is a rather slow process. For this reason I advise giving as much time as possible, and while I do not claim to having had any personal experience as a grafter, in the South, still I am inclined to think that grafting in the fall, and not later than December, would be preferable to later in winter or spring. By giving the cion and stock two or three months in which to form granulations and cohesion, there would be more certainty of success. Of course, I now refer to what is called crown grafting on the root below the surface of the ground, and when the cion is fixed in place with the usual ligatures of waxed paper or cloth, the soil is drawn back into place and the cion entirely covered with it, but very lightly over the terminal bud.
[FIG. 68]. CROWN GRAFTING ON ROOTS OF THE HICKORY.
Where small stocks are not at hand, the roots of large trees may be severed and the end partly lifted towards the surface, as shown in Fig. 68, and when grafted, allowed to remain in position until the following season, and then taken up entire or with roots enough to insure future growth. The same or a similar process may be practiced to propagate a choice variety of the hickory, and a mere severing of the roots will insure the production of suckers from near the severed end, as shown in Fig. 69.
[FIG. 69]. SPROUTS FROM SEVERED HICKORY ROOTS.
In grafting isolated stocks in this way, a small or large stake should be placed by the side of each, to indicate their position, and also protect them from being trampled upon. I make this suggestion because, in my own experience, it has often proved successful with various kinds of hard-wooded trees and shrubs that failed when grafted in the spring. Here in the North it is rather difficult, as well as expensive, to protect cions set in the open ground in the fall; but in the South it is different, and a handful of almost any coarse litter would be sufficient to prevent severe freezing.