Tyler Arboretum is part of a massive effort to restore the American chestnut species, devastated by a fungus imported on Chinese chestnut trees at the end of the nineteenth century. “Fortunately, as is the case with many ‘successful’ diseases, this fungus doesn’t kill its host—the chestnut tree’s root system survives to continue feeding the fungus with fresh chestnut stems!” said Tyler volunteer John Wenderoth. “So, we believe recovery of the species is possible.” Among more than 100 chestnut orchards in Pennsylvania, Tyler’s was started in 1997 as part of the American Chestnut Foundation’s (ACF) work to produce a hybrid tree that is resistant to the blight.
“Our native chestnut (Castanea dentate) once thrived from Maine to Georgia down the Appalachian chain, and its range spread east into the piedmont and west into Ohio,” said Wenderoth, who joined Tyler’s project as a volunteer in 2010. “It is estimated that as many as 4 billion trees were lost from the forest ecosystem.” (Only distance has prevented the blight from spreading to native chestnut trees transplanted by pioneers in western parts of the United States.)
“Some have called the American chestnut the perfect tree,” said Wenderoth. “Every fourth tree in the Northeast was a chestnut. Its plentiful and reliable nut crops were a major food source for wildlife and a cash crop for mountain folks, and the tall, straight trunks produced excellent lumber that was resistant to decay.”
Founded in 1983, TACF has been working to cross American chestnuts with disease-resistant Chinese chestnuts. Over multiple generations, surviving hybrids with demonstrated resistance are “back-crossed” with American chestnuts. The theoretical goal is to retain only the blight resistant genetic material from the Chinese species, but in practice this process may create a tree that is only a little more than 90 percent American in its genetic makeup.
In order to maintain a reservoir of American chestnut genes, Tyler’s orchard is dedicated to growing only American chestnuts. It is one of several Pennsylvania orchards that produce American nuts to supply seed for continuing breeding work at other locations around the state. Harvested in September, it produces nuts that are held in refrigerators at Penn State—a form of cold stratification required by some forest trees and other plants that allows the seeds to fully mature for spring germination.
Other Pennsylvania orchards produce seedlings for reintroducing chestnuts in test plantings around the state. TACF is organized in state chapters in order to preserve variation in the chestnut’s genome over its range from Maine to Georgia. “You know that southerners might not like the winters in Maine or Vermont,” said Wenderoth. “Trees can be that way too, just because of their genetic makeup.”
Noting that it can take about six years for a tree to flower and begin producing nuts (if it doesn’t succumb to the ever-present spores of the blight fungus), Wenderoth emphasized that this is a lengthy process. “I’m interested in growing the trees and trying to keep them healthy, but one of my principal goals is to find others who are younger than I who can sustain this project for the long haul.”