The Rush chinquapin, and other large-fruited, tall growing varieties have also been used to some extent. The resulting hybrids make handsome trees of rapid growth and bear profuse crops of very attractive nuts, but are greatly injured by blight. As experience accumulated it was found that the extreme caution used in the earlier trials to keep out foreign pollen were scarcely needed and that merely covering the pistillate blooms as soon as they could be distinguished with cotton batting is all that is necessary, and also that hybrids may be produced with considerable certainty in open pollination if the tree or branch is kept entirely free from staminate tassels and the selected pollen is promptly applied as soon as the stigmas become receptive.
Quite a number of chance or self-pollinated seedlings from choice hybrids have been raised in the hope that their good qualities might be perpetuated and the trouble and expense of grafting largely obviated but, as with most other hybrids between distinct species, the seedlings lacked sufficient uniformity to be of especial value. A few individuals turned out superior to the parent but on the whole degeneracy, from the nut-producers standpoint, appears among seedlings of hybrid chestnuts.
In 1909 the unfruited chinquapin hybrids, 68 in number, were transferred to Arlington Farm, Virginia, and two years later Bell Experiment Plot was established near Glendale, Maryland, largely for the purpose of developing blight-resistant varieties of chestnuts as far as this can be done by breeding and testing of wild forms. There are now over 2000 hybrids and seedlings of species at Bell ranging from one to ten years of age. Of the original trees planted at Arlington about 20 remain. They have formed handsome trees twenty feet high with tops almost as wide in diameter and have borne many profuse crops of nuts mostly of good quality and from three to six times as large and heavy as those of the parent chinquapin. All have been attacked by blight, the most promising one only this spring, after thirteen years of resistance to this virulent disease. All the hybrids carrying blood of native or European chestnuts were quickly killed, but those with the Japanese species as a pollen parent are still growing vigorously and bearing well, though considerably disfigured by blight.