Friday, November 18, 2005
The American Chestnut — will it grace Carlisle again?
One hundred years ago, American Chestnut trees ten feet in diameter and one hundred feet in height were common in the Massachusetts landscape. From Maine to Georgia, ecosystems depended on plentiful chestnuts to maintain populations of turkey, ruffled grouse, black bear, and other species. Many people relied on this hard, fast-growing, rot-resistant tree for food, lumber, and bark tannin.
But in 1904, blight was identified in chestnut trees growing at the Bronx Zoological Park. Spread by wind, birds, insects, and animals, the blight, introduced on nursery stock from Asia, proved unstoppable. Within fifty years virtually every mature American Chestnut, some over 400 years old, was dead. Only a small forest in Wisconsin now survives to give a taste of the grandeur that is gone.
On Tuesday, Brad Smith, acting president of the Massachusetts Chapter of The American Chestnut Foundation (TACF) brought a message of hope to the forty attendees at his talk, sponsored by the Carlisle Historical Society and the Carlisle Garden Club, at the Gleason Library. Through the scientific efforts of his organization, founded in 1983, restoration of the American Chestnut may be possible within a few years. Blight- resistance is characteristic of Chinese and Japanese chestnuts, which do not possess the size or look of the American type. But by successive crossings of American and oriental strains, TACF hopes to develop blight-resistant hybrids with the characteristics of the American Chestnut.
Immature sprouts from the stumps of dead American Chestnut trees still commonly appear, but die, usually before reaching maturity. The blight, a fungus called cryphonectria parasitica, enters bark wounds and cracks and forms a canker. The canker grows until the tree is killed. Death usually occurs within five or six years, before the tree has a chance to flower or reproduce. One of the tasks of TACF is to search out the few lucky survivors producing flowers that can be fertilized. Because chestnuts in different areas of the country displayed regional variation, local chapters of the foundation work on developing regional strains.
The goal of the Massachusetts chapter is to identify twenty large surviving trees with many female flowers. The trees must be reachable by bucket truck, as flowers appear at the top of the tree. Smith described the process of producing seed, which requires pollinating flowers from a bucket ninety feet in the air, then returning to harvest the burrs produced. "It's quite labor-intensive," he says, "and that's just the first step."
"We then select for blight resistance and American traits," says Smith. Hundreds of trees are planted to produce seven or eight with the characteristics required. Then several strains of fungus are introduced to test resistance. The best of the lot go on to the next round of cross-breeding. One hundred twenty lines are planned of one hundred trees per line, requiring space to eventually plant 12,000 trees. The goal is to produce, through successive generations, a blight-resistant hybrid that is 94% American.
The breeding program is hampered by the lack of mature chestnut trees to pollinate. Trees are constantly dying, and Smith notes with frustration that American Chestnuts are not listed as "endangered" due to the proliferation of sprouts from stumps. TACF has therefore been unable to protect some identified mature trees since lost to development. The foundation narrowly managed to purchase the only surviving chestnut forest, located on a ten square mile tract in Wisconsin, days before it was scheduled to be logged!
Questions from the audience reflected awe at the size (one stump measures fifty-three feet in circumference and seventeen feet across,) scope, and longevity of the lost chestnut, and a desire to support the on-going efforts of TACF. Smith suggested that anyone who thinks they have located a flowering American Chestnut (not a horse chestnut) can visit the Massachusetts chapter's web site at www.masschestnut.org for information on identifying and reporting their find. Other informational web sites include www.acf.org and www.charliechestnut.org for kids. "Good things are happening," concluded Smith, "But a lot more needs to be done."
© 2005 The Carlisle Mosquito