Revival of the American Chestnut
Nearly Killed by a Fungus, the Tree Returns to its Native Range
Extensive efforts are underway to revive and replant the American Chestnut in its native range.
The American Chestnut (Castanea dentate) was once one of the kings of the eastern hardwood forests of America, with mature trees towering up to 100 feet tall. From Maine to Florida and out through the Piedmont as far as the Ohio Valley, these trees were commonplace and provided whole communities with a healthy livelihood, harvesting both the excellent wood and sweet-tasting nuts each autumn.
Its wood was rot resistant and its trunks were tall and straight, making it one of the best materials to use for everything from barn rafters to fence posts. Milled and polished, its warm buttery color and interesting grain made it equally desired for furniture and millwork inside the home. Today, chestnut furniture is some of the most sought after in antique shops, and stumbling upon a vintage home with its chestnut molding intact and unpainted is a real find.
But in 1900, a chestnut blight fungus (Cryphonectria parasitica) was accidentally imported into New York via some Asian a nursery stock. The fungus took hold and spread throughout the country, slowly killing an estimated 3.5 billion trees between 1900 and 1940.
On an infected tree, a sunken canker on its trunk evidences the disease. That canker slowly grows to close off the plant’s sap system (akin to our bloodstream) and the tree slowly chokes to death. (To further explore how to identify these cankers, please see National Geographic, 1990, February issue).
While there are a few of the original trees still hanging on today, they have mainly been replaced by more resistant imports from China (Castanea mollissima) or Europe (Castanea satina) . Horse Chestnuts, Beeches and Chestnut Oaks (trees not even actually related to the American Chestnut) have also been masquerading as true chestnuts.
While the Chinese and European varieties also produce a yearly harvest of edible nuts, those who remember the sweet taste of the American Chestnut tend to agree the other varieties taste pasty and more like unroasted peanuts than the American variety.
American Chestnuts are distinguished by long, papery leaves, with large, prominent “teeth” (hence the “dentate” in its name). There is also a bristle at the end of each. Chinese Chestnuts, on the other hand, have leaves that are more oval-shaped, with much smaller, less prominent teeth. Their leaves are also much thicker and waxier than the American Chestnut.
Today, the efforts of the American Chestnut Foundation and the American Chestnut Cooperators Foundation are helping to ensure that more disease-resistant forms of the American Chestnut are replanted in their natural range. Although the two foundations share the same general goal, they differ in their methods. The American Chestnut Foundation has undertaken an intensive breeding program in Virginia, under the direction of plant pathologist Dr. Fred Hebard.
Mainly, they are crossing the American Chestnut with the Chinese Chestnut in a technique called “back-crossing.” The goal is to take these hybrid Chinese-American trees and to re-cross them with trees of the original species. Eventually, scientists hope to produce a tree that is genetically nearly identical with the Castanea dentate, but with one big difference: it is resistant to Cryphonectria parasitica. The American Chestnut Foundation hopes to release at least 100 lines of blight-resistant trees within the next few years.
Meanwhile, the American Chestnut Cooperators Foundation is intent upon breeding back to a disease-resistant American Chestnut stock, using only American Chestnut breeders. Their intensive program of back-breeding, cloning and grafting and re-claiming habitat is also beginning to yield positive results.
