The elm tree may be making a comeback in Vermont.
The majestic shade canopy has been disappearing from American streets since the 1930’s, when a tiny beetle began feasting on its bark and spreading a killer fungus. Dutch elm disease has taken a heavy toll.
But some arborists are trying to cross-breed more tolerant varieties.
That’s especially important for colleges where big elms remain campus landmarks.
In mid-September, during a damaging storm, a giant elm tree toppled onto Wilson Hall at Dartmouth College. About eighty feet tall and 145 years old, it had survived the scourge that made its toxic debut in America in the 1930’s. The Wilson elm, says College arborist Brian Beaty, probably fell for a different reason.
“I think construction was the main problem with this tree,” he said, surveying the roped-off spot where the tree once stood.
Beaty says the roots were probably damaged by digging the foundations of nearby buildings. But he says the College regularly applies fungicides to its many other elm trees, which can still be located on a campus map.
“It’s a preventative treatment and not everyone does it because it’s expensive, time consuming, there is no actual cure, once the tree has the disease you can’t cure it, so it’s part of a big program we do to prevent disease,” Beaty said.
But fungicides don’t always work, so Dartmouth also prunes or removes diseased elms trees to avoid contagion. That’s also what most American towns and cities have done—which has left very few sidewalk elms standing. But—surprisingly--Marks says the American elm is still our nation’s second most abundant species, in forests.
“And it’s very widespread, it occurs in all the parts of the Connecticut River watershed where I do my work,” said Christian Marks.
As forest ecologist for the Nature Conservancy’s Connecticut River program, Marks calls himself a “matchmaker” for elms that live far apart.
“Highly tolerant trees that have been found are in very different places,” he explained via telephone.
There’s the Princeton elm, for example, in New Jersey, and the New Harmony elm, in Ohio. Not ideal locations for a productive courtship.
“But if I plant a New Harmony and a Princeton next to each other for example, they can cross and produce offspring some of which will be even more tolerant than their parents. Some of it will be less tolerant,” Marks said.
Marks is conducting these fertility experiments at several forests in the Champlain Valley and along the Connecticut River. He says the most promising nursery site is in Maidstone, where 100 per cent of the newly planted species have survived. In a few years, he hopes, they will spawn sturdy children. But not all of them will be suitable for urban planting. So even if the elm makes a comeback, it may not ever be the sidewalk icon it once was.
