Then in 1904, disaster struck. Chestnut blight, caused by a lethal Asian fungus, was discovered on trees in the Bronx Zoo. Unlike Chinese counterparts, American trees had no resistance and the plague spread rapidly. By 1950, the keystone species that had covered 9 million acres of Eastern forest was gone, reduced by 99.99 percent to just a few isolated individuals. The horse chestnut, Aesculus hippocastanum, which drops its glossy fruit on sidewalks in the eastern United States, isn't even in the Castanea genus of true chestnut trees.
Horse chestnuts are extremely bitter and inedible.
Most of the chestnuts available in stores today are from European species. Between the 1930s and the 1960s, the U.S. Department of Agriculture and the Connecticut Experiment Station tried to breed blight-resistant American chestnut hybrids, but the project failed and was abandoned. Through successive generations, over a span of 30 to 50 years, the new hybrids are backcrossed with entirely American parents. The foundation, at work since 1983, estimates that by 2006, such trees will exist and by 2012, they will yield nuts that might be used in reforestation. Members are eligible to buy purebred American chestnut seeds and seedlings from the foundation.