American chestnut

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American chestnut
Castanea dentata
American chestnut leaves and nuts
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Rosids
Order:Fagales
Family:Fagaceae
Genus:Castanea
Species:C. dentata
Binomial name
Castanea dentata
(Marsh.) Borkh.
Natural range of Castanea dentata
 
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American chestnut
Castanea dentata
American chestnut leaves and nuts
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Rosids
Order:Fagales
Family:Fagaceae
Genus:Castanea
Species:C. dentata
Binomial name
Castanea dentata
(Marsh.) Borkh.
Natural range of Castanea dentata

The American chestnut, Castanea dentata, is a large, monoecious deciduous tree of the beech family native to eastern North America. Before the species was devastated by the chestnut blight, a fungal disease, it was one of the most important forest trees throughout its range. There are now very few mature specimens of the tree within its historical range, although many small sprouts of the former live trees remain. However, there are hundreds of large (2 to 5 ft diameter) trees outside its historical range, some in areas where less virulent strains of the pathogen are more common, such as the 600 to 800 large trees in northern lower Michigan.[1][2]

Description[edit]

Castanea dentata is a rapidly growing deciduous hardwood tree, historically reaching up to 30 metres (98 ft) in height, and 3 metres (9.8 ft) in diameter. It ranged from Maine and southern Ontario to Mississippi, and from the Atlantic coast to the Appalachian Mountains and the Ohio Valley. It has several related chestnut species, such as the European sweet chestnut, Chinese chestnut, and Japanese chestnut, which are distinguishable from the American species by a few morphological traits such as leaf shape, petiole length and nut size. C. dentata was once one of the most common trees in the Northeastern US. In Pennsylvania alone, it is estimated to have comprised 25-30% of all hardwoods. The tree's huge population was due to a combination of rapid growth and a large annual seed crop in comparison to oaks which do not reliably produce sizable numbers of acorns every year. Nut production begins when C. dentata is only 7–8 years old.

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 (5–8 in) long and 7–10 cm (3–4 in) broad, also tend to average slightly shorter and broader than those of the sweet chestnut. The blight-resistant Chinese chestnut is now the most commonly planted chestnut species in the US, while the European chestnut is the source of commercial nuts in recent decades. 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, but are not closely related to the horse-chestnut, which is in the family Sapindaceae.

The chestnut is monoecious, producing many small, pale green (nearly white) male flowers found tightly occurring along 6 to 8 inch long catkins. The female parts are found near base of the catkins (near twig) and appear in late spring to early summer.

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, with 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.

Chestnut blight[edit]

Once an important hardwood timber tree, the American chestnut is highly susceptible to chestnut blight, caused by an Asian bark fungus (Cryphonectria parasitica, formerly Endothia parasitica) accidentally introduced into North America on imported Asiatic chestnut trees. The disease was first noticed on American chestnut trees in what was then the New York Zoological Park, now known as the Bronx Zoo, in 1904, by chief forester Hermann Merkel. While Chinese chestnut evolved with the blight and developed a strong resistance, the American chestnut had little resistance. The airborne bark fungus spread 50 mi (80 km) a year and in a few decades girdled and killed up to three billion American chestnut trees. Salvage logging during the early years of the blight may have unwittingly destroyed trees which had high levels of resistance to this disease and thus aggravated the calamity.[3]

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 m (20 ft) in height before blight infection returns.

Young tree in natural habitat

The total number of chestnut trees in eastern North America was estimated at over three billion, and 25% of the trees in the Appalachian Mountains were American chestnut. The number of large surviving over 60 cm (24 in) in diameter within the tree's former range is probably fewer than 100. Huge planted chestnut trees can be found in Sherwood, Oregon, as the Mediterranean climate of the West Coast is not conductive to the spread of the fungus, which relies on hot, humid summer weather. American chestnut thrives as far north as Revelstoke, British Columbia. Although large trees are rare east of the Mississippi River in modern times, it exists in pockets of the blight-free West, where the habitat was agreeable for planting: settlers brought seeds for American chestnut with them in the 19th century. At present, it is believed that survival of C. dentata for more than a decade in its native range is almost impossible. The fungus utilizes Northern red oak as a host, and while the oak itself is unaffected, any American Chestnuts nearby will quickly succumb. In addition, the hundreds of chestnut stumps and "living stools" dotting Eastern woodlands may still contain active pathogens.

American chestnut field trial sapling from the American Chestnut Cooperators Foundation

Several organizations are attempting to breed blight-resistant chestnut trees. 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 Chinese chestnut into American chestnut, to recover the American growth characteristics and genetic makeup, and then finally intercrossing the advanced backcross generations to eliminate genes for susceptibility to blight. The goal is eventually to restore the species to the eastern forests of North America. Backcrossed trees were first planted back into the forest for testing in 2009. In 2005, a hybrid tree with mostly American genes was planted on the lawn of the White House.[4] A tree planted in 2005 in the tree library outside the USDA building is still very healthy seven years later; it contains 98% American chestnut DNA and 2% Chinese chestnut DNA. This tree contains enough Chinese chestnut DNA to resist the blight which is essential for restoring the American chestnut trees into the Northeast.[5] The Northern Nut Growers Association (NNGA) has also been active in pursuing viable hybrids.[6] From 1962 to 1990, Alfred Szego and other members of the NNGA developed hybrids with Chinese varieties which showed limited resistance. Other researchers, such as those at the State University of New York (SUNY), are trying to attack the blight with viruses or are creating trees that are genetically modified (GM) to resist the fungus, and could be the first GM forest trees released in the wild in the United States.[7][8]

Surviving specimens[edit]

American chestnut leaves, late spring

Uses[edit]

The nuts were once an important economic resource in the US, being sold on the streets of towns and 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 typically 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 without extensive preparation.

The wood is straight-grained, strong, and easy to saw and split, and it lacks the radial end grain found on most other hardwoods. The tree was particularly valuable commercially since it grew 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, paper pulp, 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.

This tree is not considered a particularly good patio shade tree because its droppings are prolific and a considerable nuisance. Catkins in the spring, spiny nut pods in the fall, and leaves in the early winter can all be a problem. These characteristics are more or less common to all shade trees, but perhaps not to the same degree as with the chestnut. The spiny seed pods are a particular nuisance when scattered over an area frequented by people.

See also[edit]

References[edit]

  1. ^ Brewer, L. G. 1982. The present status and future prospect for the American chestnut in Michigan. Mich. Bot. 21: 117–128.
  2. ^ Fulbright, D. W., W. H. Weidlich, K. Z. Haufler, C. S. Thomas, and C. P. Paul. 1983. Chestnut blight and recovering American chestnut trees in Michigan. Can. J. Bot. 61:3164–3171.
  3. ^ "The American Chestnut Tree, reprinted from American Forestry". 1915. 
  4. ^ "Trying to Light A Fire Under Chestnut Revival". The Washington Post Company. December 29, 2005. Retrieved October 29, 2010. 
  5. ^ "GreenXC". American Chestnut Restoration Breakthrough. Archived from the original on July 8, 2011. Retrieved June 28, 2011. 
  6. ^ http://www.nutgrowing.org/
  7. ^ The chestnut resurrection. Nature - 03 October 2012
  8. ^ Wines, Michael (July 13, 2013). "Like-Minded Rivals Race to Bring Back an American Icon". New York Times. Retrieved July 14, 2013. 
  9. ^ Chestnut's Last Stand. Dnr.wi.gov. Retrieved on April 19, 2012.
  10. ^ "Macon News". 
  11. ^ "Birmingham News Article – Trees Found". 
  12. ^ "Crescent News – Trees Found". 
  13. ^ "Daytona Daily News – Trees Found". 
  14. ^ "APS – virus attacks blight". 
  15. ^ "Daytona Daily News – Blight altitude restricted". 
  16. ^ "AP – Rare American chestnut tree discovered in Sandusky marsh". 
  17. ^ Kentucky tree may help bring chestnut back. Ktsaf.org. Retrieved on April 19, 2012.
  18. ^ Tuesday June 2: A Rare Tree Find. Wmur.com. Retrieved on April 19, 2012.
  19. ^ [1]"Chestnut Ridge Wilderness – Proposed", A Citizens' Wilderness Proposal for Pennsylvania's Allegheny National Forest 
  20. ^ "Trees and Ornamental Shrubs: American chestnut [English page]". Montreal Botanical Garden. Space for Life Montreal. Retrieved 6 July 2013. 
  21. ^ "Heritage Trees of Portland: Trees by Species". Portland Parks & Recreation page. City of Portland. Retrieved 6 July 2013. 

External links[edit]