Chestnut

The American chestnut tree, Castanea dentata, is native to the rich hardwood forests of the northeastern United States and southeastern Canada. It was once a dominant species in forests of this region, occurring over an area of approximately 9 million acres (3.6 million ha), and particularly abundant in southern Appalachia. The American chestnut was an economically important tree. At one time, chestnuts contributed about one-tenth of the sawlog production in the United States. Its nuts were gathered as food for humans, were eaten by livestock, and were a staple for wild species such as turkeys, passenger pigeons, and forest rodents.

The American chestnut was nearly wiped out by the introduction of chestnut blight fungus (Endothia parasitica). This fungus is a wind- and animal-dispersed pathogen that was inadvertently introduced with horticultural planting stock of an Asian species of chestnut (Castanea crenata) imported to New York. The first symptoms of chestnut blight in the American chestnut were seen in 1902, and within 25 years it had been virtually eliminated as a canopy species in the deciduous forest of eastern North America, being replaced by other shade-tolerant species of trees. Many individuals of the American chestnut survived the blight, as their root system was not killed. They regenerated by growing stump-sprouts, but once these trees grew tall, they were again attacked by the fungus and knocked back. Efforts have been made to breed a light-resistant variety by crossing the American chestnut with Asian species. This has been somewhat successful and the hybrid chestnuts are now available as shade trees. Unfortunately, this is not likely to help the American chestnut, a native tree species, become prominent in the forests of eastern North America once again. It is possible, however, that the introduced blight pathogen will evolve to be less deadly to the American chestnut.