Remember to watch all ties in grafting to prevent strangulation of the tender new growth. This, with removal of sprouts or suckers from the stock below the graft are two very important features of after-care, and neglect can nullify the most expert work in the grafting operation.
In grafting the black walnut I prefer to use the side graft because of the bleeding problem. This is precisely the same as the modified cleft graft except that the cleft is made about three-fourths of an inch below the apex of the stock. By making the graft a little below the top of the stock one can tie and wax it, without waxing the top of the stock, which is permitted to bleed at will. This freedom to bleed relieves the pressure of the sap at the graft, where healing takes place without flooding.
For stocks under an inch in diameter, I use the splice and modified cleft grafts exclusively. For larger stocks, such as are encountered in top working, other methods are preferred.
One can cut the main stock off just above a small limb, and graft one or more of the limbs. Again, one may cut the large stock off a year in advance, and bud or graft one or more of the suckers that are thrown out.
If neither of the above methods are applicable, one can use either the simple bark graft, or the slot bark graft.
In making the simple bark graft, I cut the stock off at a 45 degree angle as for the modified cleft graft. The scion is prepared by making one long wedge face, and on the other side make two short faces so that the point is triangular.
To insert the scion make a cut through the bark downward from the apex of the stock. Insert the scion between the bark and the stock, with the long face next to the wood, and force gently down until just a little of the face of the wedge shows above the top of the scion. It is well, in case the stock is large, to place three or four scions around the stock, removing all but the strongest after a year of two.
This graft is satisfactory for thin-barked species, but for the hickory, the slot bark graft is preferable.
For this graft, the scion should be trimmed as a wedge, with one face about twice as long as the other. Two parallel cuts are made through the bark at the top of the stock a distance apart equal to the width of the scion wedge. This strip of bark, or "tongue" is loosened at the top, and the wedge is forced between it and the wood, with the long face next to the stock, as in the simple bark graft.
Secure tying and waxing should be practiced in all grafting. Small nails or tacks driven into the top of the stock will help in anchoring the tying material to the sloping surface.