Of the nut trees grown in this area, the chestnut has been the most difficult to propagate by budding. Nurseries in the upper South have propagated their pecan and walnut trees mostly by patch-budding or the similar ring-budding method, with very good success. When applied to chestnuts, patch-buds have seldom grown. The common T-bud, likewise, has been a general failure on chestnuts in America, though reported successful in Japan. Chip-buds have not been much-better.
Several years ago, Dr. Max B. Hardy told me that the inlay bark-graft had been used successfully with Chinese chestnuts at the U.S.D.A, laboratory in Albany, Ga., following Dr. B. G. Sitton's use of this method with pecans in Louisiana. (It is described in a bulletin from Michigan State College, East Lansing, Mich.) I tried it in a small way, and had some success using it on chestnuts in July and August. This spring I suggested it to Mr. Roark and Dr. Richards, both of whom tried it out, using Castanea mollissima stocks and various scion varieties.
Mr. Roark used the inlay bark-graft in the spring, topworking a C. mollissima seedling with scions of the Colossal, a hybrid variety from California. About 50 per cent of these have grown this year. Dr. Richards tried it during July, on C. mollissima seedlings from a different source. None of the Colossal would grow on his trees, but he was partially successful with scions of the C. mollissima varieties, Hobson, Carr and Zimmerman. He then devised a variation in the method which was highly successful with C. mollissima varieties. This I shall call the Richards "Twin-T" bud.
In "Twin-T" budding, a vertical slit is made in the bark of the stock. Then horizontal cuts are made through the bark at both top and bottom of the vertical cut. The bud piece is cut from the well matured part of a current season's twig, leaving a rather thick slice of wood beneath the bud. (It may be as thick as half the diameter of the twig.) The bud is inserted in the stock as in ordinary T-budding, then wrapped with a large sized rubber budding strip. (Westinghouse electrician's tape and Curity adhesive tape have also been used. Some other brands poisoned the buds.) The "take" of Chinese chestnut buds by this method has run from 60 to 90 per cent on Dr. Richards' trees of various sizes this year. In a short nursery row, buds were placed under first or second year bark, while larger trees were topworked by placing the buds mostly under the bark of second year limbs.
The Colossal failed again on Dr. Richards' trees when budded by the "Twin-T" method, but Carr and other Chinese varieties were budded successfully. The graft-compatibility problem in chestnuts is one of considerable complexity. Thus Carr, which has presented incompatibility with certain stocks of C. mollissima at other places, grew on these trees, and Colossal, compatible on another C. mollissima tree, failed on trees which are apparently compatible with Carr. The Chinese chestnut species varies in its graft-compatibilities possibly as much as in other characteristics (growth, productivity, size and quality of nuts, etc.) so that nut nurserymen should begin to select their seed for chestnut understocks with a view toward getting strains with a greater degree of compatibility to the leading scion varieties.
Mr. Roark has been able to propagate the Colossal upon its own roots by layering a small tree in his orchard. Two limbs pegged into the ground in the spring of 1945 had produced roots a year later, and were then detached from the parent tree. This is a slow but sure method of propagating nut tree varieties that are not congenial with the stocks available for grafting or budding. He has also layered sweet cherries and prune trees by this method which is described in U.S.D.A. Farmers Bulletin 1501 with reference to filberts.
A Heartnut Variety Compatible with Black Walnut Stocks
Seedling black walnuts are common on farms of west Tennessee. Dr. Richards and Mr. Rhodes have been most active in showing that these can be topworked readily to improved black walnut varieties under the conditions prevailing there. Mr. Rhodes has also fruited such older Persian walnut varieties as Lancaster, Mayette, and Franquette on black walnut stocks, but finds them generally unproductive in his climate. Newer varieties, including some selections of the Carpathian strains are now being tried and should be of fruiting age soon. Mr. Rhodes has also found, at Covington, a heartnut that is vigorous and productive under west Tennessee conditions. He finds that it buds readily on the native black walnut. Some budded trees of it are over a dozen years old. They have medium sized nuts, smooth shelled (with fairly thick shells for a heartnut) and kernels of good flavor, coming out whole when the nuts are cracked carefully. I am giving this variety the name Rhodes, and suggesting it for use in west Tennessee because of its adaptability and the fact that it can be budded upon black walnut. Others have reported Japanese walnut (including heartnut) varieties incompatible with black walnut at other locations. Dr. Richards has propagated some other heartnut varieties on black walnut, but finds them more variable than the Rhodes, in obtaining a good union.
Paper Wrap Gives Summer-Long Protection to Transplanted Trees
Too commonly, transplanted nut trees suffer from sunscald injury on their southwest sides during the first summer in the orchard. This injury is particularly common on pecans, which suffer a severe shock from transplanting and are slow in re-establishing vigorous growth. In west Tennessee, as one grower puts it, "A pecan is doing well if it holds one green leaf its first year." Pecans have been known to remain dormant in their tops until the second spring after planting, and then start growth. During this initial period of establishment in the orchard, it is beneficial to give some kind of shade to the tree trunk, to keep the bark from "cooking" and dying on part of the most exposed side. Waxing of the trunks before planting helps reduce drying out of the tops before the roots are partially regenerated and top growth begins, but waxing alone, under our conditions, is not sufficient to prevent the frequent occurrence of a dead area starting on the southwest side of the trunk during the summer following tree setting.