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A jolt for the science behind harvesting maple sap

Scientists find way to harvest without taps or buckets or, even, what you’d call trees

Ron Wenzel inspected 400 buckets on trees that produce thousands of gallons of maple sap in Hebron, Conn.JOANNE RATHE/GLOBE STAFF

UNDERHILL, Vt. — Scientists at a research lab deep in the maple woods of northern Vermont have made a discovery that could revolutionize New England’s most tradition-steeped form of agriculture. But their work may also threaten a cherished way of life.

Experiments at the University of Vermont’s Proctor Maple Research Center show that maple sap — the raw material that sugar makers boil into syrup — can be efficiently vacuumed from the decapitated trunks of saplings, sharply increasing syrup production. That’s a radical departure from the centuries-old practice of inserting a small tap a few feet above the base of a mature tree, relying on the force of gravity and internal pressure to draw off the sap.


Instead of tapping big trees in a forest setting, the new technique would use juvenile trees grown in tight crop-style rows, like grapevines or Christmas trees.

The research has generated giant buzz across the so-called syrup belt, a swath of 10 states stretching from Wisconsin to Maine, plus four Canadian provinces, where the end of winter brings a short stretch — usually only a month or so — of the freezing nights and mild days that force the sap to flow.

The new technique could give sugar makers a hedge against global warming, which is already blamed for reducing the duration of sugar season by 10 percent during the past 50 years; there are fewer of the critical days that cycle between freeze and thaw. Saplings respond those temperature shifts more quickly than mature trees, allowing for more frequent sap runs and large yields even during shorter seasons.

The experimental extraction method involves vacuuming sap from the trunk of a decapitated maple sapling.SALLY MCCAY/UNIVERSITY OF VERMONT

Use of young trees should also give sugar makers more opportunity for genetic experimentation — breeding trees that yield sweeter sap, for example, or that better resist disease and insect damage. The Asian long-horned beetle, an invader from China that has appeared in at least 15 states, including Massachusetts, voraciously attacks mature maples. But the insect largely ignores saplings.


Sugar maple forests bristling from rugged slopes rank among the most revered features of the New England landscape. Few traditional harvesters are immediately enamored by the idea of abandoning the wild trees for bunched rows of saplings, each with a plastic vacuum tube protruding from its chopped top. But radical ideas, the sugar makers quickly note, have a way of becoming reality if they make money.

“This doesn’t seem like pie-in-the sky science. It looks like something that some day will come into wide use in sugar country,” said Laura Sorkin, co-owner with her husband Eric of a 67,000-tap sugar bush on 1,000 acres in Cambridge, Vt., one of the state’s largest maple operations. A well-run maple forest can produce 40 to 50 gallons of syrup per acre, after processing.

“It could economically benefit the industry. But it may force maple production out of the woods and into tidy farm rows, like any agribusiness,’’ said Sorkin, who is also a food writer. “And that’s sad. Maple is the last major wild harvest food crop,’’ except for commercial offshore fishing.

The research by Timothy Perkins, director of the university’s maple research center, and plant biologist Abby van den Berg, shows that saplings shorn of their crowns — and with a vacuum device clamped atop the cut — will act like straws, sucking sap directly from the roots while also pulling groundwater into the tree, where it is sweetened by the maple’s unique chemistry.


Syrup produced from saplings should be identical in taste, clarity, and color — indicators of quality rigorously monitored by Vermont and most other states — to syrup produced from mature trees, van den Berg said.

“It could economically benefit the industry. But it may force maple production out of the woods and into tidy farm rows, like any agribusiness. And that’s sad,” said Laura Sorkin, co-owner with her husband, Eric, of a 67,000-tap sugar bush on 1,000 acres in Cambridge.Handout

The startling results were the outgrowth of more prosaic research into whether vacuum pressure might coax more sap from mature trees.

“Instead, we discovered that vacuum-induced flow makes the upper tree unnecessary for sap production,” Perkins said in an interview. “It changes the basic paradigm.’’

Perkins and van den Berg, whose ongoing experimentation with saplings started in 2010, say their aim is not to replace traditional sugar making, only to make it more versatile.

They believe plantation-style plots will one day occupy a crucial niche in the maple industry. “This could give sugar makers a tool to expand their operations and increase their bottom line,” said van den Berg.

“Maple is Vermont’s signature agri-food product. But farmers can’t always expand because so much sugar bush is already in use,” she said. “And when mature stands are badly damaged — by an ice storm, say — it can take a [human] generation or more to replace the maples.’’

A sugar maple needs 35 to 50 years to grow to a size that can be commercially tapped. The trees grow in semi-wild forests, known as sugar bushes, at heights of from 50 to 80 feet.

The research suggests maple saplings can be grown from seedling to productive size in less than a decade — making such an operation comparable to Christmas tree farms, which not too many decades ago also seemed a bizarre and unnatural form of silviculture. Unlike Christmas trees, however, saplings would not necessarily be a “one harvest” crop. Perkins and van den Berg believe the trees might be tapped over several years, at least, by lopping off the regenerating crown a few inches below the previous year’s cut.


Moreover, the University of Vermont studies indicate that tapping densely-planted saplings could yield a 10-fold increase in sap production per acre.

“Instead of 100 taps per acre, it would be possible to place 5,000 taps per acre,” Perkins said. “Instead of 40 gallons of maple syrup per acre” — a typical yield for a traditional sugar bush — “it would be possible to get 400 gallons per acre.”

Some analysts are skeptical. “I believe it is technically feasible, but the economics are murky,” said Michael Farrell, head of Cornell University’s maple research center. “A lot of upfront costs seem to be involved. The technology isn’t ready for real-life operations. Detailed financial modeling [and more experimentation] will be necessary.”

Sugar season, which typically starts in late February and runs four to six weeks — depending on weather — is just getting underway in the region. Sugar makers have placed their taps and rigged untold miles of plastic tubes from the trees to stainless steel collection tanks

“There’s a lot of technology already driving the maple industry,’’ said Jacques Couture, who has tapped maples for 42 years on the family farm in Westfield, Vt.


Sasha, a golden retriever, kept watch at Maple Ledge Farm in Sturbridge, where sap is collected from buckets and tubes.JOANNE RATHE /GLOBE STAFF

“But the maple harvest retains a special mystique,’’ he said. “We draw sap from those trees, we profit from those trees, but we also protect and cherish those trees. We pass them down through generations. I’ve got trees on my land that have been tapped since 1892.’’

Until the late decades of the 20th century, maple sugaring was a colorful but marginal cottage enterprise, a way for farmers to squeeze a few dollars from land too steep to cultivate or even pasture cows.

That’s changed drastically. Vacuum tubing has replaced traditional sap buckets. Reverse osmosis devices — all gleaming steel, humming parts, and flashing digital read-outs — remove much of the water from the sap before it even reaches the evaporating pans. And the boiling pans themselves are these days mostly fired by oil or gas, not split wood.

The result: Production is soaring and profits are solid. Vermont, the largest maple maker, by far, in the United States, last year produced 1.3 million gallons of syrup, more than a threefold increase from a decade before. (Total US production grew from 1.5 million gallons to 3.2 million gallons during the same period.) The value of the syrup to the Vermont economy has shot to nearly $40 million a year, according to federal data.

The United States represents only 20 percent of world production — Quebec is the colossus of syrup, pouring out 75 percent of the global supply.

In northern New England, a fresh generation of entrepreneurs is moving into maple production: Vermont saw 3.8 million taps placed in 2013, compared with 1.5 million just 10 years earlier. For now, newcomers have only two startup options — buy or rent an existing sugar bush. Or plant trees and wait half a century or so for the first profitable gush.

“Of course, no one really plants a sugar bush the way they plant tomatoes — the time frame is too long,’’ said Sam Cutting IV, chairman of the Vermont Sugar Makers Association and president of Dakin Farm, a Ferrisburgh, Vt.-based retailer and mail-order seller of maple products.

“A working technology may be a few years off, but sugar makers are eventually going to grasp this new opportunity and build something profitable,’’ he said “One very attractive thing about this method is that it might keep more land in agriculture.’’

Asked whether sapling plantations — with thousands of trees planted in uniform ranks — represents an ugly departure from classic sugaring, Cutting replied: “Compared to what? More condos? Bigger box stores? Because that’s where much farmland is going, to development.’’

The University of Vermont has filed an international patent application for “sap collecting devices, systems, and methods for sap-producing saplings.’’ The application contains schematics showing how saplings might be planted in rows containing 5,000 to 10,000 dwarfish trees — each topped by a vacuum-tight cap with a spigot connecting to collection tubes.

“The technology might upend the industry,’’ said Sorkin. “But sugar makers will still be boiling up a pure maple product. Harvest methods may look different. Some of the romance may go. But the sap will be the same; maple syrup will remain an all-natural ambrosia.’’

Colin Nickerson can be reached at