Once king of eastern forests, the American chestnut was wiped out by blight. Now it is poised to rise again.
The first warning signs came in 1904, when rust-coloured cankers developed on chestnuts at the Bronx Zoo in New York. Zoo forester Hermann Merkel took a sample across the street to the New York Botanical Garden, where mycologist William Murrill soon identified the spores as chestnut blight.
The blight probably hitched a ride on nursery imports of Japanese chestnuts beginning in 1876. Spreading through rain and air, fungal spores infected trees through bark wounds and breaks. Cankers developed, quickly encircling a branch or trunk and cutting off the supply of water and nutrients from the soil. Within 50 years, the blight had laid waste to nearly the entire population of some 4 billion trees.