The American chestnut: Cultivating a comeback

  • Blight on an American chestnut is seen at Smith College’s Ada and Archibald MacLeish Field Station in West Whately. STAFF PHOTO/ANDY CASTILLO

  • Paul Wetzel points out blight in an American chestnut at Smith College’s Ada and Archibald MacLeish Field Station in West Whately. Staff PHOTO/ANDY CASTILLO

  • A stand of American chestnut trees at Smith College’s Ada and Archibald MacLeish Field Station in West Whately. STAFF PHOTO/ANDY CASTILLO

  • Last year, Paul Witzel says, he cut down about 75 blight-stricken trees at Smith College’s Ada and Archibald MacLeish Field Station in West Whately. STAFF PHOTO/ANDY CASTILLO

  • Last year, Paul Witzel says, he cut down about 75 blight-stricken trees at Smith College’s Ada and Archibald MacLeish Field Station in West Whately.

  • A Chinese chestnut tree, pictured above, is resistant to blight. STAFF PHOTO/ANDY CASTILLO

  • STAFF PHOTO/ANDY CASTILLO STAFF PHOTO/ANDY CASTILLO

For the Gazette
Published: 3/7/2020 1:42:16 PM

While he was a college student in Worcester, Brian Clark of Ashfield remembers when he read for the first time about the American chestnut, once known as “America’s most iconic tree,” which by then had become decimated by blight — from Mississippi to Maine.

Back in Ashfield, his father, Malcolm, told him, “Oh yeah, I remember going out on Ridge Hill when I was a kid with my mother to collect chestnuts.” His father also remembered later trying to get a chestnut sprout from a neighbor’s farm to grow, without success.

The fast-growing American chestnut, which could reach 100 feet tall and 10 feet in diameter, had light, straight-grained wood that was popular for furniture and timber, shingles and flooring. The wood had also been used by Native Americans for dugout canoes, its leaves and bark had medicinal properties, and its nuts were a nutritious food supply for humans and wildlife.

Clark, who is now vice president of the American Chestnut Foundation’s Massachusetts-Rhode Island Chapter, examined a grove of about 3,000 chestnut trees recently at Smith College’s Ada and Archibald MacLeish Field Station in West Whately — some of them the smaller, multi-stem Chinese chestnut, which is blight resistant. Most, though, were American chestnut saplings, planted from seeds collected around the region by the roughly 300-member foundation.

Now in its eighth year, this 1-acre orchard is one of three test plots of American chestnuts in Franklin County — there are also two research groves in Conway and Hawley, including a 150-acre plot in Conway State Forest. They are part of an effort by conservationists to breed in resistance to the blight to restore this functionally extinct grand tree to American forests.

The method, developed in the late 1970s by American Chestnut Foundation founder Charles Burnham, breeds blight resistance into the American chestnut by “backcrossing” the best characteristics of American and Chinese varieties. In theory, the hybrid would blend 94 percent American and 6 percent Chinese genes, but this percentage may be up for reassessment given what’s been learned about the Chinese blight resistance. 

Paul Wetzel, who oversees the Whately test orchard as a staff ecologist for Smith College’s Center for Environmental and Ecological Design and Sustainability, points to the rusty-colored wound of the blight on a sample tree just above where it was inoculated as part of an ongoing experiment to see which of the Chinese-American hybrids are most blight resistant. The blight girdles the stem, locking the tree’s cells above to prevent water from being carried up. Below the canker, the chestnut’s roots and stem can live on and send out shoots that may reach 15 feet or more before succumbing to blight again. Millions of American chestnuts thus survive, but very few reach the stage where they are able to flower and reproduce.

The Whately breeding grove boasts hybrids from 20 different genetic lines from Chinese chestnuts, combined with seeds from American chestnuts from around Massachusetts and Rhode Island, in an attempt to bring about as much diversity as possible.

With 16 American Chestnut Foundation chapters, it’s hoped that maximum genetic diversity can produce trees that fight off blight as well as other pathogens or predators to make a comeback over time.

“Even though it’s all the same species, there may have been some local adaptations to the environmental conditions across such a big region,” Wetzel said. “The idea of having local chapters is to take local trees and cross them with the Chinese trees, so if there is some local adaptation that gets passed into the genetics, it will still be there.  It’s estimated there were 4 billion American chestnuts in North America before the blight, and if all of a sudden it funnels down to 500 or 1,000, there’s a huge genetic bottleneck. If you just took a tree that’s growing in Maine and started propagating it, you’d essentially have a monoculture across the whole area.”

For that reason, he said, it’s important to be mindful of ensuring there’s a diverse genetic pool, regardless of what species is being reintroduced.

With climate change, there are also concerns that a different pathogen that rots the tree’s roots — but which has been a problem only in the South where ground freezing doesn’t occur — may begin moving northward as well.

Efforts to bring back the American chestnut stir not only the imagination, Wetzel says, but also cultural memories about a tree that was such a core part of Eastern forests.

“The chestnut was a very culturally important tree to eastern North America. It had the most economic value of any species of tree. It grows fast, it grows in many different areas, except for wet areas, and the wood is strong, it’s easy to work and it’s rot-resistant. It produces great nuts, they’re very high-protein and produced a lot of food for wildlife. There’s this whole cultural background. People talked about roasting chestnuts and buying it off the streets in big cities. It was the original fast food.”

As chestnut advocates try to accelerate regeneration, Wetzel says, “We thought we were pretty close. We thought we were creating seeds that are resistant, but then we’re finding out, if you look at 150 trees, most of them have some blight canker on them, and I’ve already cut down the worst ones. The original Burnham program was designed on the assumption that only two to three genes were involved in resistance.”

It’s now thought that at least nine genes, according to Wetzel, are responsible for the resistance of the smaller, orchard-size Chinese chestnut trees, and it’s been thought that hybrids with their American cousins might need just 45 percent of the American chestnut genetic makeup to advance its more familiar characteristics.

Advocates are seeing they need to step up their effort by lowering expectations from a tree that’s 94 percent American, and crossing more Chinese varieties that have natural resistance to the blight. There are also efforts to develop a cost-effective way to test younger saplings for resistance, as well as tests of a “transgenic” approach to hybridize an American chestnut seed with the same kind of natural blight resistance that occurs in wheat and other grains.

The work is important, and much of it is done primarily by volunteers. Funding comes primarily from American Chestnut Foundation members.

Using seeds available from the foundation, Clark has an American chestnut growing in front of his house that he guesses is more than 35 feet tall, part of a grove that he’s hoping will continue to flourish. But getting the trees to make a real comeback on a wider scale, he and Wetzel say, will take time, more research — and plenty of patience. 

Recently retired, Richie Davis was a writer and editor for more than 40 years at the Greenfield Recorder. He blogs at richiedavis.net.




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