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.