Tapped Out? UVM Studies Long-Term Effects Of Sap Vacuums On Maple Trees

Jun 5, 2017

Maple syrup producers have an ever-growing arsenal of high-tech tools to draw more and more sap out of the trees. Now, scientists at the University of Vermont are doing a long-term study to see if modern tapping systems are affecting the health of maple trees.

Modern vacuum systems draw out about twice the amount of sap that traditional buckets collect. Abby van den Berg, an associate professor at UVM's Proctor Maple Center, says there are no indications that modern tapping techniques hurt the trees, but researchers still want to dig deeper.

"We don't really think that we're doing anything very much more impactful than we have always been doing, but we don't know if we're taking some critical component at a time that's critical for the tree," says van den Berg. "Those are the more detailed questions that really need to be looked at and refined."

Vacuum systems allow maple syrup producers to cheat Mother Nature. The trees still need cold nights and warm days to make the sap flow, but a vacuum pump can help draw out more sap.

Van den Berg says syrup makers are getting better every year at using the systems to increase their yield from each maple tree.

"We have better technology and better vacuum pumps, and everything is more refined," she explains. "Over time, we get even better at applying some of the technology that's been around quite some time. And with all the changes, vacuum systems are probably the number one difference-maker."

Researchers at the Proctor Maple Research Center in Underhill are using about 90 trees to study the long term effects of modern vacuum systems on the health of the maple trees.
Credit Howard Weiss-Tisman / VPR

The Proctor Center has cordoned off 90 trees in its research forest in Underhill.

A third of the trees aren't being tapped at all and another third have traditional buckets hanging on them. In the last group, the scientists are using the most modern and aggressive tapping methods during sugaring season.

They'll keep the experiment going, for at least 10 years, to see if the high-tech vacuum systems affects the health of the trees.

"We don't really think that we're doing anything very much more impactful than we have always been doing, but we don't know if we're taking some critical component at a time that's critical for the tree." — UVM Associate Professor Abby van den Berg

Mike Doten's family has been making maple syrup up in the hills around Pomfret for more than a century.

And as Doten has been taking over the operation from his father, he's been kind of slow in embracing all of the technology connected to the maple industry.

He's got a fancy evaporator, but it's wood-fired, because Doten says it makes better syrup. And next year, he'll finally replace all of the tin buckets with plastic tubing.

But he doesn't think the latest high-tech vacuum systems are good for his sugarbush.

Mike Doten stands near an old cast iron maple syrup evaporator on his farm in Pomfret. Doten has embraced some modern technologies, but he doesn't think vacuum systems are good for his trees.
Credit Howard Weiss-Tisman / VPR

"I don't eschew technology all together, but I think there's certain things that it's not necessarily the best for," Doten says. "If you got a real serious vacuum, and you're really sucking the sap out of the trees. I just can't imagine that's really particularly good for the trees. The sap is the lifeblood of the tree."

But Dan Crocker, who runs Sidelands Sugarbush in Westminster, says the vacuum systems are healthier for his trees.

A sign on the shed at Sidelands Sugarbush in Westminster tells visitors about the modern vacuum system that was just installed.
Credit Howard Weiss-Tisman / VPR

Crocker has one of the most advanced vacuum systems in the state.

He says when the pump is working right, he needs to drill fewer holes in his trees, which improves the long-term health of his maple trees.

"We've been doing it here for 35 years, and our trees are completely healthy," he says. "They heal right up. They look great. We've had caterpillar attacks and ice storms, and they just keep rolling on."

Crocker's vacuum pump is state-of-the-art. He just installed it this year, and it cut his electric bill by more than half.

Crocker prides himself on staying up-to-date on the most modern technological advancements in the maple industry. He's a big fan of the work that's done at the Proctor Center, but he doesn't expect any big surprises from van den Berg's study.

"People think we're sucking sap out, but that's a misunderstanding,” he says. "The cold nights and warm days cause the pressure in the trees to change, and the vacuum system just lets us control that more." Crocker says his trees are his life, and he'd never introduce a technology if he thought there was a chance of doing harm.

He'll complain about the fluctuating wholesale price of maple syrup, and about the big-time investors who are gobbling up land and building sugarbushes that dwarf his operation in southern Vermont. But if there's a sustainable way to draw out a little more sap each spring, he's all for it.

And he says he can't wait to fire up his new vacuum pump again next year.