Until a century ago, the American chestnut (Castanea dentata) was the cornerstone tree species of eastern North America. With long, straight trunks and bushy crowns, it carpeted the forest floor each autumn with prickly brown nuts. But the arrival of chestnut blight (Cryphonectria parasitica) from Asia wiped out almost all the stately trees, leaving only a few, isolated stands. Since then, a faithful fan club of scientists and citizens has sought to tame the blight.
As chief scientist of the American Chestnut Foundation (ACF), a group of chestnut enthusiasts and scientists, Hebard has bred thousands of hybrids at the organization’s research farm in Meadowview, Virginia. He crosses descendants of the original American chestnut with the much smaller Chinese variety (Castanea mollissima), which has some natural immunity to the Asian fungus. And after decades of work, he is within reach of his goal, a tall American tree with enough Chinese traits to keep it healthy.
[…] Once researchers have a resistant chestnut, the question is where to plant it. Forest ecosystems have transformed in the past century, and reintroducing the chestnut could upset the new ecological balance. “You can’t assume that a forest with chestnut is better than a forest without. You can’t roll the clock back,” says Steve Hamburg, chief scientist at the Environmental Defense Fund in Boston.
“Reintroduction is going to be kind of a gradual thing,” says Jacobs. In 2009, the ACF began planting restoration chestnuts on US Forest Service land in Virginia, Tennessee and North Carolina. In April 2012, it also started planting hybrid chestnuts and other hardwood saplings at a former mining site.
For chestnut lovers, other signs of hope stand alongside a path at the New York Botanical Garden. In a corner of the garden, a transgenic chestnut and a restoration hybrid both reach about a metre high. Although their leaves have shrivelled a bit, the scrappy saplings have managed to survive one of the warmest summers on record. And their bark is smooth, with no sign of the cankers that claimed their ancestors.