RETURN OF THE KING
Science has revived one favorite of yesteryear, the American elm. Can it do the same for the American chestnut?
By Marty Carlock
On a weedy acre-plus plot outside Boston stand 330 tree saplings,
their trunks sheltered by collars of aluminum flashing and cylinders
of plastic mesh. They’ve been there for four growing seasons. Some
are as tall as 15 feet, and most look vigorous. These are American
chestnuts, a species destroyed by chestnut blight in the first half
of the twentieth century.
In a few years the small trees that survive here will be
inoculated with the blight fungus, Cryphonectria
parasitica. Some will die. Some won’t because they are scions of
cosmopolitan parents, a blend of American chestnut genes with those of the
Chinese chestnut, resistant to the disease. If all goes well, descendants of
these resistant chestnut trees—and others—may be available to landscape
architects within a decade.
Chestnut restoration research lags in the wake of
development of disease-resistant American elms, another species almost wiped
out by blight—Dutch elm disease, in that case. But there’s a difference, says
John Emery, who is in charge of this batch of experimental seedlings. “The
chestnut project is more ambitious; it’s an attempt to resuscitate an entire
Elm trees that become blighted can be treated with thiabendazole,
a fungicide that must be injected so as to spread throughout the
crown of the tree. There is no such medication for chestnuts, which
must either fight off the disease on their own or succumb. While
treatment is available for elms, trees on the market today are all
clones taken from a few trees found to be naturally more or less
immune to Dutch elm disease. “It’s a cookie-cutter approach,” Emery
points out. “There’s not the diversity.” Even so, those graceful,
vase-shaped trees, once thought lost forever, are becoming common
again in the nation’s townscapes.
The renascence of the chestnut, by contrast, is based on
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