American chestnut

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The American Chestnut (Castanea dentata), a member of the beech family (Fagaceae), was once the most important forest tree throughout much of the eastern United States and southeasternmost Canada. A rapidly growing tall and broad deciduous hardwood tree, it reached up to 45 m (150 feet) tall, 30 m (100 feet) across, with a trunk up to 3 m (10 feet) in diameter, and ranged from Maine and southern Ontario to Mississippi, and from the Atlantic coast to the Appalachians and the Ohio valley. There are several related chestnut species such as the European Sweet Chestnut, Chinese Chestnut and Japanese Chestnut, which are distinguishable from the American species. C. dentata can be best identified by the larger and more widely spaced saw-teeth on the edges of its leaves, as indicated by the scientific name dentata, Latin for "toothed". The leaves, which are 14-20 cm long and 7-10 cm broad, also tend to average slightly shorter and broader than those of the Sweet Chestnut (16-28 cm by 5-9 cm). The chestnuts are related to beech and oak; they are entirely unrelated to the horse-chestnuts (buckeyes) in the genus Aesculus.

American Chestnut male (pollen) catkins

The American Chestnut is a prolific bearer of nuts, usually with three nuts enclosed in each spiny green burr, and lined in tan velvet. The nuts develop through late summer, the burrs opening and falling to the ground near the first fall frost.

The American chestnut was a very important tree for wildlife, providing much of the fall mast for species such as White-tailed Deer and Wild Turkey and formerly the Passenger Pigeon. Black Bears were also known to eat the nuts to fatten up for the winter (and still do in those rare instances where they can still encounter the nuts.)

Chestnut blight

Young tree in natural habitat

Once an important hardwood timber tree, the chestnuts are highly susceptible to an Asian bark fungus or "chestnut blight" (Cryphonectria parasitica formerly Endothia parasitica) accidentally introduced to America on Chinese Chestnut ornamental nursery stock at the Bronx Zoo in 1904. While Chinese Chestnuts evolved with the blight and are immune, the airborne bark fungus spread 50 miles a year and in a few decades girdled and killed the billions of American Chestnuts. Fortunately, the stumps survive and send new shoots, and so the species has been saved from extinction, although the stump sprouts rarely reach more than 6 m (20 feet) in height before blight infection returns.

It is estimated that one out of four trees within its range were American chestnut, for a total of some 3.5 billion trees. The number of surviving mature trees can now be counted in the mere dozens, due to the blight. The finest surviving trees (featured in National Geographic) can be found in Sherwood, Oregon, as much of western North America is still free of blight. American chestnut thrives as far north as Revelstoke, British Columbia.

American Chestnut field trial sapling from the American Chestnut Cooperators Foundation

Several organizations are attempting to breed blight-resistant chestnuts. One of these is the American Chestnut Cooperators Foundation, which breeds surviving all-American chestnuts, which have shown some native resistance to blight. The Canadian Chestnut Council is a Canadian organization attempting to reintroduce the trees in Canada, primarily in Ontario. Another is The American Chestnut Foundation, which is backcrossing blight-resistant American Chestnut/Chinese Chestnut hybrids to American parents, to recover the American growth characteristics and genetic makeup, and then finally intercrossing the advanced generations in order to breed consistently for blight resistance. The eventual goal is to reintroduce the species to the wild. In 2005, a hybrid tree with mostly American genes was planted on the lawn of the White House, and to date is doing very well.

The United States National Arboretum also has taken an interest in the American chestnut, using similar methods of backcrossing to create hybrids resistant to blight. Overall, it is anticipated that the species may be ready for trial plantings in the wild in about six years.

On 18 May 2006, a biologist with the Georgia Department of Natural Resources spotted a stand of roughly half a dozen trees near Warm Springs, Georgia. One of the trees is approximately 20-30 years old and 13 m tall, and believed to be the southernmost chestnut tree yet discovered that is capable of flowering and producing nuts [link]. These trees are not thought to be a blight-resistant variety, but perhaps gained resistance through the dry, rocky micro-climate or other conditions in the area they were found. Representatives from the American Chestnut Foundation will study the trees, and perhaps cross-pollinate them with blight resistant trees. An unusually large (26 m tall, 35 cm diameter) survivor was found in Talladega National Forest, Alabama in June 2006 [link].

Uses

The nuts were once an important economic resource in the U.S., even being sold on the streets of larger cities, as they sometimes still are during the Christmas season (usually "roasting on an open fire" so their smell is readily identifiable many blocks away). Chestnuts are edible raw or roasted, though preferably roasted. Nuts of the European Sweet chestnut are sold in many stores. One must peel the brown skin to access the yellowish-white edible portion. Note that the unrelated horse-chestnut's 'conkers' are poisonous.

The wood is straight grained, strong as oak, although easier to saw and more easily split, lacking the radial end grain found on most other hardwoods. The tree was particularly valuable commercially since it would grow at a faster rate than oaks. Being rich in tannins, the wood was highly resistant to decay and therefore used for a variety of purposes, including furniture, split-rail fences, shingles, home construction, flooring, piers, plywood, paperpulp, and telephone poles. Tannins were also extracted from the bark for tanning leather. Although larger trees are no longer available for milling, much chestnut wood has been reclaimed from historic barns to be refashioned into furniture and other items. "Wormy" chestnut refers to a defective grade of wood that has insect damage, having been sawn from long-dead blight-killed trees. This "wormy" wood has since become fashionable for its rustic character.

External links

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