But trouble arrived when another species of chestnut was imported to the U.S. from Asia in the late 1800s. The trees, known as Chinese chestnuts, carried a dangerous fungus—an organism that lives by feeding on organic material. The trees from Asia were resistant to this fungus, known as chestnut blight. American chestnuts were not. The fungus swept through the American population, killing the trees from the trunk up, while leaving their root systems intact. By the 1950s, the American chestnut was functionally extinct. The species still existed, but because of the blight, new trees couldn’t grow large enough to produce another generation. Without help, the tiny American chestnuts Greene spotted on Mount Ella would face the same fate.
When the tornado cleared away vegetation on Mount Ella, it gave sprouts the chance to shoot up from surviving chestnut tree roots, says biologist Jared Westbrook, TACF’s director of science. But when this happens, sprouts don’t usually live long. “If they do grow tall, they will get the blight and die back,” says Westbrook.