American Chestnut
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 American Chestnut leaves and nuts
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| Castanea dentata (Marsh.) Borkh. |
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The American Chestnut (Castanea dentata) was one of the most important forest trees throughout much of the eastern United States and southeasternmost Canada. A rapidly growing deciduous hardwood tree, it reached up to 30-45 meters (100-150 ft) tall and 3 meters (10 ft) in diameter, and ranged from Maine and southern Ontario to Mississippi, and from the Atlantic coast to the Appalachian Mountains and the Ohio Valley. There are several related chestnut species such as the European Sweet Chestnut, Chinese Chestnut and Japanese Chestnut, which are distinguishable only with difficulty 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 centimeters (5-8 in) long and 7-10 centimeters (3-4 in) broad, also tend to average slightly shorter and broader than those of the Sweet Chestnut. The blight resistant Chinese Chestnut is the most commonly planted chestnut species in the U.S. It can be distinguished from the American Chestnut by its hairy twig tips which are in contrast to the hairless twigs of the American Chestnut. The chestnuts are in the beech family along with beech and oak, and are not closely related to the horse-chestnut which is in the family Sapindaceae.
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.
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[edit] Chestnut blight
Once an important hardwood timber tree, American Chestnut is highly susceptible to chestnut blight, caused by an Asian bark fungus (Cryphonectria parasitica, formerly Endothia parasitica) accidentally introduced to America on imported Asiatic chestnut trees. The disease was first noticed on American Chestnut trees in the Bronx Zoo in 1904. While Chinese Chestnuts evolved with the blight and are usually immune, the airborne bark fungus spread 50 miles a year and in a few decades girdled and killed billions of American Chestnuts. New shoots often sprout from the roots when the main stem dies, so the species has not yet become extinct. However, the stump sprouts rarely reach more than 6 meters (20 ft) in height before blight infection returns.
It is estimated that the total number of chestnut trees in eastern North America was over 3 billion, and that 25 percent of the trees in the Appalachian Mountains were American Chestnut. The number of large surviving American Chestnut trees over 60 cm (24 inches) in diameter within the tree's former range is probably less than 100. Huge planted chestnut trees (featured in National Geographic) can be found in Sherwood, Oregon, since much of western North America is still free of blight. American Chestnut thrives as far north as Revelstoke, British Columbia.
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 an 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 goal is eventually to reintroduce the species to the eastern forests of North America. 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 forests by 2010.
Two of the largest surviving American Chestnut trees are in Jackson County, Tennessee. One is the state champion and has a diameter of 61 cm (24 in) and a height of 23 meters (75 ft) and the other tree is nearly as large. One of them has been pollinated with hybrid pollen by members of The American Chestnut Foundation; the progeny will have mostly American Chestnut genes and some will be blight resistant. On 18 May 2006, a biologist with the Georgia Department of Natural Resources spotted a stand of several trees near Warm Springs, Georgia. One of the trees is approximately 20-30 years old and 13 meters (40 ft) tall and is the southernmost American Chestnut tree known to be flowering and producing nuts [1]. Another large tree was found in Talladega National Forest, Alabama in June 2005.[2]. It is 26 meters (85 ft) tall with a diameter of 35 centimeters (14 in). A combination of factors may account for the survival of these relatively large American Chestnut trees including low levels of blight susceptibility, hypovirulence (the attacking blight fungus is weakened by a virus), and good site conditions; in some cases, large chestnut trees have been lucky, and have not yet been exposed to the blight-causing spores.
[edit] 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 now sold instead in many stores. One must peel the brown skin to access the yellowish-white edible portion. The unrelated horse-chestnut's "conkers" are poisonous.
The wood is straight-grained, strong, easy to saw and split, and lacks 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.
[edit] Future
The intrinsic and economical value of returning the American Chestnut tree to its former place in the Eastern forest is incalculable. It was known as the redwood of the eastern forests and in many areas was the dominant tree of the forest. It is thought that panic logging during the early years of the blight may have unwittingly destroyed trees which had resistance to this disease and thus aggravated this calamity.[3]
[edit] External links
- Flora of North America RangeMap:
- The American Chestnut Foundation
- American Chestnut Cooperators Foundation
- Canadian Chestnut Council
- National Geographic article
- The American Chestnut Tree, reprinted from American Forestry, 1915
- Chestnut in the Future, reprinted from American Forestry, 1915
- Castanea dentata images at bioimages.vanderbilt.edu
- Rare American Chestnut Trees Discovered (Washington Post, May 19, 2006)
- Resurrecting The American Chestnut
- New Hope for the American Chestnut
- Restoring the American Chestnut Tree to Alabama
