By C. A. Reed, Bureau of Plant Industry United States Department of Agriculture
The northernmost zone of the eastern part of the United States, within which conditions appear at all encouraging for the planting of the hardiest varieties of nut trees now available, may be outlined as covering the milder portions of Massachusetts, Rhode Island, Connecticut, New York, Michigan, Wisconsin, Minnesota and South Dakota. Beyond the Canadian border this zone should perhaps include the fruit belt of Ontario known as the "Niagara Peninsula," which skirts Lake Ontario from the City of Hamilton to the Niagara river. No doubt it should also include considerable Canadian territory immediately adjacent to Lakes Erie and St. Clair, and north to the lower end of Lake Huron.
In each American state within this general zone there are numerous localities to which several species of edible nuts are indigenous, others where the butternut alone is found, and still others to which none of the common kinds appear to be adapted. Climate and soil are both limiting factors within this general section. No nut trees are likely to prove hardy to the extent of bearing heavily where winter temperatures are extremely trying or where soils are not of high grade. A fundamental principle involving plant ecology, which with reference to planted nut trees is too often lost sight of, is that, regardless of species, plants are unlikely to be altogether hardy in any locality where minimum temperatures of winter are appreciably lower, or growing periods much shorter, than at the place where the variety in question originated. For example, it is often assumed that a pecan tree native to southern Texas, the lowest point of the range of this species in the United States, should do well in southeastern Iowa, the northernmost point within the range. Likewise, it is also sometimes assumed that a black walnut variety originating in Arkansas, Texas or Tennessee should be hardy in the black walnut belts of New York, Michigan, Wisconsin, Minnesota, Pennsylvania, or wherever the species is indigenous or has been successfully transplanted.
There are definite degrees of hardiness which must not be overlooked. A species or variety may be hardy enough to grow thriftily for many years, and to make a splendid tree, hundreds of miles north of the latitude at which it will mature occasional crops; or it may be able to produce crops that are frequent in occurrence yet indifferent as to character; or there may be occasional crops of first-class nuts; but good crops of good nuts are exceedingly rare when the minimum temperatures of winter or the length of the growing period are appreciably more adverse than in the locality where the variety originated.
A few illustrations may help to make these points clearer. On the Experimental Farm of the U. S. Department of Agriculture at Arlington, Va., directly opposite Washington, on the Potomac, there are five pecan trees of the Schley variety which originated on the Gulf coast of Mississippi. These trees have grown splendidly since being planted more than 20 years ago. They blossomed and set nuts more or less regularly after they were about eight or ten years of age, but it was only in the eighteenth year that a season was late enough in fall for a single nut to mature. Another case is afforded by a pecan seedling, probably from Texas, called to the writer's attention by Dr. W. C. Deming, Hartford, Conn., which stands near the outskirts of that city. This is a large, beautiful tree. It rarely sets crops of nuts, and when it does the nuts fail to become more than half or two-thirds normal size by the time of autumn frosts. The kernels are then quite undeveloped and the nuts therefore worthless each year.
In another case, near Ithaca, New York, the Stabler walnut from Maryland and the Ohio from Toledo, of the state after which it was named, all appear to be congenially situated insofar as environment is concerned until the nuts are actually harvested and cured. The nuts of each variety appear normal when they drop from the trees, but during the process of curing, the kernels wither up too badly to be marketable. The Thomas from southeastern Pennsylvania is somewhat better able to adjust itself to Ithaca conditions, but it is far from being a commercial success in that region.
Kinds of Nuts
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.
The Native Group
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.