Bringing back the ‘mighty giant’
Ashfield man’s goal: American chestnut tree that’s blight-resistant
ASHFIELD — The chestnut blight fungus came in on Asian nursery plants shipped into New York harbor sometime around 1900 and it destroyed about 4 billion American chestnut trees over the next 50 years, according to the American Chestnut Foundation.
Before the blight, at least a quarter of all the trees in the New England/Eastern Appalachian Mountain Range were American chestnuts — the so-called “mighty giants” that grew to over 100 feet tall, towering over other forest trees and providing wildlife with nutritious nuts that were more plentiful than acorns or beechnuts, according to Brian Clark, an Ashfield apple orchard owner who is working to restore the tree.
Like an evil genie that couldn’t be put back into its bottle, the chestnut blight fungus is still carried on airborne spores on the backs of birds and animals. Even the stump sprouts that occasionally blossom from American chestnut tree stumps eventually die of exposure to blight, says Clark.
Clark is on the board of directors for the state chapter of the American Chestnut Foundation. For the last 10 years, he has been cultivating backcross-breeds of the American chestnut and Chinese chestnut tree in hopes of eventually creating American Chestnut seed stock that has only one gene from its Chinese ancester: resistance to chestnut blight.
Clark’s current crop of chestnuts are four generations removed from the 50 percent American and 50 percent Chinese chestnut.
Their genetic composition is about seven-eighths American chestnut.
The backcross breeding is done by pollinating the Chinese chestnut with the American chestnut, planting the seeds and growing trees. These young trees are innoculated with the chestnut blight and the weakest, least blight-resistant trees are culled.
The American chestnut mother tree is then pollinated from the most blight-resistant hybrids and the process is repeated, until a seed is produced that can be planted to grow blight-resistant American chestnut trees.
Clark has set aside a 2-acre orchard for chestnut trees to speed up a process that might take hundreds of years, if left to evolution.
About two years ago, Clark innoculated about 600 trees with the blight, and of those, only 25 were left standing. The other trees were either killed by the blight or were culled because they did not show levels of resistance.
The healthy survivors are cross-bred again, the new seeds are nurtured into seedlings or planted as seeds. When they mature, they are innoculated with the blight and thinned out.
“We have 600 to 700 trees now,” says Clark. “There were 1,200 trees before I started thinning them out. I set out 120 to 130 trees this spring. About last year, we (planted) 300 to 350.”
The difference between American and Chinese chestnut trees, he explained, is that the Chinese chestnut was bred and cultivated for hundreds of years to be a food source. He said this blight-resistant chestnut resembles a bush more than a tree and is not used for timber.
Besides being a primary food source for wildlife, the American chestnut tree also produced fine, sturdy lumber.
“Loggers tell of loading entire railroad cars with boards cut from just one tree,” says an American Chestnut Foundation pamphlet that Clark hands out.
“I joined the foundation in 2002, and we started the orchard in 2003, in Hawley,” said Clark, a seventh-generation farmer in this region.
Clark grew up on his Apple Valley farm and first learned about the American chestnut decimation when he was in college. About 27 years ago, while living in Minnesota, Clark learned about a group of growers in Michigan who were working to restore the chestnut. He moved back to Ashfield after his retirement from IBM in 2007.
Clark said their are seven different family “lines,” with seeds coming from different mother trees.
“Now we are doing open pollination. This summer, they blossomed and cross-pollinated each other to produce this generation.”
Clark said “it’s not clear” that the American chestnut could ever evolve a natural resistance to the blight.
“There are still hundreds of stump sprouts in the woods. But, because a (chestnut) tree doesn’t self-pollinate, you have to have two trees in close proximity. Sprouts may even grow up before they get knocked down by the blight again,” he explained. “There isn’t any chance for the evolution to happen, to develop resistance for these populations. And there are other things that kill chestnut.”
This summer, Smith College agreed to a 30-year commitment to produce an American chestnut “seed orchard” on part of 240-acre MacLeish Field Station land.
Seed orchards are designed to produce seeds of better quality than those that can be produced naturally. Clark said the Foundation would like to recruit more growers to help with the seed orchard project.
For more information, go online to the American Chestnut Foundation website:
You can reach Diane Broncaccio at:
or 413-772-0261, ext. 277