Most of us won’t notice the bloom and fade of elm tree blossoms.
For one thing, healthy elm trees are few and far between: Most of them on this continent succumbed decades ago to Dutch elm disease.
Furthermore, by common standards of beauty, the blossoms of an American elm are unremarkable. Each bud is about the size of a pencil eraser. Its folds are a dull reddish-brown. What few insects flit around in early March pay them little or no mind.
“They’re wind-pollinated, so they don’t need to be pretty,” explained Christian Marks, as he examined a healthy, bud-loaded branch in Charlotte. “The wind doesn’t care.”
Marks, on the other hand, cares deeply about what happens to the pollen from this particular tree — the sole adult survivor in a farm hedgerow near Dorset Road.
The Massachusetts-based floodplain ecologist with nonprofit The Nature Conservancy is part of a team of scientists working to rescue and fortify the iconic tree species.
Although not immune to elms’ aesthetic charms, the collaboration places an even higher value on the tree’s ability to anchor stream banks and foster a species-rich ecosystem along rivers.
Those heroics begin at the microscopic scale.
Pollen from solitary “survivor” trees like the one in Charlotte has little opportunity to fertilize other disease-tolerant individuals.
To stave off what might become a genetic dead-end for the fragile species, Marks and others have collaborated for several years on a program that is a combination dating service, fertility clinic, birthing center, and nursery.
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Controlled cross-pollination with other disease-tolerant elms in New England, they say, is boosting the odds for subsequent generations’ survival. This year they plan to add the genes from 20 old-timer trees into the mix.
“We’re trying to preserve enough diversity so the species can respond to this disease in as many ways as possible — so elms can continue to evolve as the disease evolves and as new threats develop,” Marks said.
The current threat: Just one in 10,000 American elms are estimated to have any significant tolerance to Dutch elm disease.
Timing is everything
The soil beneath the tree was damp and rich in clay — the sort of consistency and texture that can weigh down and even claim a loose-fitting boot.
Along much of the field-side hedgerow stood the haggard remains of dozens of dead and dying elm saplings.
“There’s lots of Dutch elm disease through here,” Marks said. “It’s an old tree; it’s probably been exposed multiple times. Usually when a tree gets Dutch elm disease it’s dead within the year.”
This elm’s tolerance to the fungal infection isn’t absolute, he added: One major branch appears to have been killed by the disease.
But the tree’s ability to thrive despite that onslaught suggests that its pollen will carry some promising DNA, Marks said.
At eye level, the elm’s flower buds were swollen, but still closed. They wouldn’t remain closed for long, he said.
Marks strode back to his truck and began assembling a yard-long cardboard box.
In an hour or so would dispatch a clutch of bud-laden branches by overnight delivery to a U.S. Forestry Service laboratory in Delaware, Ohio.
Charlotte resident Brenda Waters stood nearby and watched. She has lived in the shadow of this sturdy elm for 29 years.
Her daughter, Chea Evans, pulled out several old photographs, in which the tree served as a background.
It’s always been big, the two women confirmed, and it’s getting bigger.
They turned to watch Macintosh Swan, of Shelburne-based Limbwalker Tree Service, anchor a climbing rope around its trunk using a “farmer’s loop” or circus bowline knot.
He slung the other end around a sturdy looking limb high in the elm’s crown, about 80 feet up.
“Flower buds tend to be better out at the tips and at the top,” Swan said. “And for my purposes, it’s easier to move around as much of the tree as possible from the highest-possible tie-in point.”
He tested the strength of the limb, then strapped himself into a harness laced with carabiners and safety buckles.
Suddenly, without warning, Swan boosted himself up the rope. Within 10 seconds he became a speck in a very tall tree.
He pulled a pruning saw from a scabbard strapped to his calf and got to work. Every several minutes, he pitched another inch-thick branch down to earth.
Saplings at work
Marks collected what Swan tossed down, handling them carefully to avoid damage to the emerging blossoms.
He trimmed them to fit the shipping box and wrapped the cut ends with damp cloth and a plastic wrap to keep them from drying out.
Marks worked quickly; he was eager to get his cargo delivered.
The soon-to-be-released pollen would be applied to the blossoms of other disease-tolerant elms at the Ohio facility.
In a month or so the recipient trees — the “mothers,” Mark calls them — will produce seeds. That quick reproductive turnaround is part and parcel of the elm’s unique ecological niche.
“If you’re growing in a floodplain, spring flooding brings in new sediments,” Marks said. “You want the dropping of seed to coincide with when the floodwaters recede — so you can have them fall in these perfect seedbeds.”
Seedlings coddled by Forest Service botanists in Ohio will be delivered back to Vermont, to a nursery at Green Mountain College in Poultney.
When the plants reach between three and five feet tall, they’ll be transplanted in floodplain restoration projects near Canaan.
Inch-thick saplings will be subjected to systematic “field trials” by scientists at the Vermont Fish and Wildlife Department.
“Some of the forest service researchers will come out and actually inject the disease into the trunk of those trees,” Mark said. “We’ll see what symptoms they develop; which ones die; which ones survive.”
The results will yield a better understanding of the kind of resistance the parent tree has, as well as how that resistance is passed through its progeny, he said.
“Hopefully some of the saplings will have the kind of high tolerance to the disease that we can release them to the public and use them to help restore the species throughout its range,” Marks said.
Insurance premiums
Despite the early-March rush to secure one old elm’s genetic blueprints, most scientists believe it will take decades to assess if the species will be able to go forth and multiply without human help.
Some signs of the elm’s resurgence, such as changes in streamside fauna and flora, might be subtle and slow to recognize, Marks said. “There are a lot of small things that change a floodplain community,” he said.
Large elms literally shore up those communities.
“There’s something called the ‘insurance hypothesis’ that argues in favor of having a lot of species in an ecosystem,” Marks continued.
“Whenever you lose one, you have other species that can take their place,” he said. “And so you want to want to keep that diversity as much as you can because it creates a resiliency. You can respond better to tragedies, whatever they may be.”
Humans who seek striking visual evidence to support that hypothesis might be advised to keep their eyes on a floodplain forest canopy.
Bald eagles, Marks said, show a strong preference for nesting in elm trees.