Chestnut

Chestnut

The sweet chestnut

The American chestnut

Chestnuts are species of trees in the genus Castanea, family Fagaceae. They are species of temperate hardwood (angiosperm-dominated) forests found in the Northern Hemisphere and are indigenous to eastern North America and Eurasia. Species in the genus Castanea can grow to be 100 feet (30 m) tall. They have simple leaves with a broadly toothed margin and sweet-smelling, yellowish, insect-pollinated, early-summer flowers aggregated on a long flowering axis. Fertilized flowers develop into prickly, tough-coated fruit, containing 2-3 large, rich-brown colored, edible seeds (or nuts). True chestnut seeds should not be confused with horse chestnuts, or buck-eyes, genus Aescellus, which have somewhat poisonous seeds.

The wood of all chestnut species can be manufactured into an open-grained decay-resistant lumber. It has a rich brown color and can be worked easily to manufacture fine furniture and musical instruments. Chestnut is also used for its durability in construction timber, railway ties, pit props, and shingles.

The sweet chestnut

The sweet chestnut (Castanea sativa ) is a cultivated species originally native to southern Europe and Asia Minor. There are extensive plantations in parts of southern France, Italy, and some other countries. This tree grows 30-100 feet tall (9-30 m), with wide, spreading branches. The nuts of the sweet chestnut are highly nutritious, containing about 80% starch and 4% oil. Chestnuts are eaten roasted or boiled, or sometimes ground into flour and used to make cakes. In 1999, the global crop of sweet chestnut was harvested from about 630, 000 acres (255, 000 ha) and had a production of 573, 000 tons (521, 000 tonnes).

The American 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 and 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 ; see below) 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.

Other chestnuts

The Japanese chestnut (Castanea crenata ) and Chinese chestnut (Castanea mollissima ) are species of eastern Asia. They are resistant to chestnut blight and have been introduced to North America as shade trees.

Bill Freedman