American Chestnut
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| Missing image American_Chestnut.JPG American Chestnut leaves and nuts | ||||||||||||||
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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 45m (150 feet) tall, 30m (100 feet) across, with a trunk up to 3m (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 difficult to distinguish 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, 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.
AmericanChestnutPollen.JPG
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Chestnut Blight
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.
Surviving trees
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.
Nuts
The American Chestnut is a prolific bearer of nuts, usually found in sets of three, enclosed in a 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. These 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.
Wood
The wood was 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.
Importance to Wildlife
The American chestnut was also a critically important tree for wildlife, providing much of the fall mast for wildlife 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.)
Breeding for Blight Resistance
Several organizations are attempting to breed blight-resistant chestnuts. One of these is the American Chestnut Cooperators Foundation, at
http://www.ppws.vt.edu/griffin/accf.html
which breeds surviving all-American chestnuts, which have shown some native resistance to blight. Another is The American Chestnut Foundation at
http://www.acf.org
which is backcrossing blight resistant American/Chinese 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.
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.
External links
- Flora of North America (http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500325)