The kinds of nuts suitable for this northern zone naturally divide themselves into three main groups, viz., native, foreign and hybrid. The last might well be divided into three sub-groups, as native hybrids, foreign hybrids, and hybrids between native and foreign species. It is perhaps true that there should also be a fourth subgroup to which chance hybrids should be assigned when there is uncertainty as to which of these three others a given variety may belong.
Of these three main groups that of the native species is at present by far the most important. It includes the black walnut, _Juglans nigra_; the butternut, _J. cinerea_; the shagbark hickory, _Hicoria ovata_; the sweet hickory, _H. ovalis_; the pignut hickory, _H. glabra_; the American sweet chestnut, _Castanea dentata_; the American beech, _Fagus americana_; and two species of native hazelnut, _Corylus americana_; and the beaked hazelnut, _C. rostrata_.
The black walnut is placed at the head of the native group because of its great all round usefulness. Wherever it grows well its timber is of leading value among all American species. It is a splendid ornamental and the nuts are highly edible. The black walnut range does not extend as far north as does that of the butternut, yet wherever it grows well it is much more useful as a tree, and is successful under a greater variety of conditions. It is probably a more dependable bearer and, upon the average, the nuts yield a higher percentage of kernel. Many more varieties of black walnut than of butternut have been brought to light and more trees have been propagated. Enough varieties of promise have originated in Michigan alone (largely as a result of the work of Prof. James A. Neilson of East Lansing) to preclude any obvious need, at present at least, of bringing varieties from farther south into this zone. In addition to these, a number of other varieties have been recognized from equal latitudes, as in New York and, west of Lake Michigan, in Wisconsin, southeastern Minnesota and northern Iowa.
ADAMS--The Adams black walnut is a rather small variety with an approximate size range of from 34 to 48 nuts per pound, and an average of 39. In a cracking test of the 1930 crop, conducted after the kernels had become too dry for most satisfactory cracking, the yield of quarters was 16.75 per cent; that of small pieces 7.81 per cent, and the total 24.56 per cent. The nuts are much elongated in form, being sharply pointed at each end. Many are quite symmetrical, thin-shelled and, when not too dry, of excellent cracking quality. The kernels examined have been notably bright in color, firm in texture, very sweet and highly pleasing to the palate. The quarters are long and slender.