The Stanley shellbark, H. laciniosa, is completely at home on the shagbark, apparently, but has not yet borne with me.
The Hatch bitternut grew luxuriantly on shagbark for a year but blew off.
The Zorn hybrid made a growth of one foot on shagbark but then was winter killed, apparently.
I have a back pasture full of vigorous pignuts, H. glabra, which for eleven years I have been grafting with faith which now seems childlike, that soon I would have fourteen acres of bearing hickory trees. Yet as a result of all these years of grafting the only hickories that I have found to thrive are the Brooks, which appears to be vigorous, the Terpenny, which is vigorous and bearing nuts in its fourth year, and possibly the Barnes. Not a single pecan survived more than a year, though many started. The Beaver hybrid makes a long spindling growth and then, in the first or second year, the leaves turn yellow and mosaic and the growth dies. The Kirtland, Kentucky, Hales, Taylor and several others, have all with me, proved failures on the pignut. Mr. Bixby's experiments appear to be showing somewhat different results.
The question of the compatibility of species and varieties is really a very important one because in some localities either the pignut or the mockernut is the prevailing species, and we wish to know with what species and varieties they may be successfully grafted. For instance, if the Barnes, which is an excellent shagbark, will do well on both the pignut and the mockernut, where so many other varieties fail, and the Brooks is at home on the pignut, these are highly important facts to be known by the man with fifteen acres of hilly woodland full of young pignuts and mockernuts.
Size of Stocks
I prefer stocks of moderate size, up to three inches in diameter. One gets greater results for the labor with these than with larger trees. Of course a tree of any size may be topworked but the labor is disproportionately greater, especially in the after care.
Cutting Back Stocks for Topworking
I doubt if it is important to cut back stocks during the dormant season, except that then there is more time. With larger trees this counts for a good deal, but in the smaller ones I like to cut them off just where I want to graft at the time of doing so. However, they may be cut off when dormant at the point of selection for grafting and later grafted without further cutting back. This reduces, or does away with the risk of bleeding. Except in very small stocks it is better to leave a number of the lower branches to prevent bleeding. When bleeding does occur it may be checked by making one or more cuts with the knife or saw into the sapwood of the trunk below the graft. Better results come when the cutting back is of the top branches and not the lower ones because of the stronger flow of sap toward the top of the tree. In my opinion a side branch should always be left at the point where the stock is cut off to maintain a circulation of sap. Otherwise the stub will often die back and the graft fail. Also, the cambium close to a side branch will be observed to be thicker and I infer that the circulation of sap is more active. I prefer to cut off the top half, or two-thirds of the tree and graft into the top and the side branches near the top.
Hickories in full foliage may usually be cut back without evident harm. Occasionally a tree will be apparently shocked to death. Sometimes when a tree in foliage is cut back severely the remaining leaves will turn black and partly, or completely, die, but the tree will throw out vigorous new growth later.