This is a discussion of several species of hickory as stocks on which to graft the named varieties of shagbark, shellbark and hybrid hickories. We have never had any experience grafting pecan as we are too far north for it. This paper is limited to the species with which we have had experience.
SWEET PIGNUT, Carya ovalis
This species will be discussed first because it is the poorest stock of any of the hickory species which we have used. This is probably because it is a tetraploid while the shagbark, shellbark and hybrids are diploids.
We have grafted many of the named varieties of hickory onto pignut stocks, using several thousand scions. We have found only one variety (the Davis shagbark) that will grow on pignut stock. We have heard of one or two others but have never tried them.
Nearly all varieties grow well the first season but fail to leaf out the following spring. They appear to winterkill. Davis has continued to grow on it for over fifteen years but growth is slower than on shagbark or bitternut stocks.
PIGNUT, Carya glabra
I have never been able to positively identify this species of pignut. Pignuts growing here vary considerably in roughness of the bark, some being smooth while others are as rough as the shagbark. In other respects they are essentially the same, all having seven leaflets per leaf. However, I have observed a very few pignut trees having smooth bark and five leaflets per leaf. The leaves are finer and smaller than on the seven leaflet trees.
These may be the glabra species, but if so, grafting results have been no better on these than on the seven leaflet trees.
As nursery stock the pignuts are worthless. However if one has some nice young pignut trees growing where he wants them, it is feasible to graft them to Davis or some other variety which has proven its ability to grow on pignut stocks. It is not advisable to graft hickory trees growing in dense woods.
MOCKERNUT, Carya alba