University of Vermont

Vermont Quarterly

New method explores alternative sugaring

Abby van den Berg and Tim Perkins
Maple researchers Abby van den Berg and Tim Perkins have discovered a new way to harvest sap. Photograph by Sally McCay


New method explores alternative sugaring

Four years ago, Tim Perkins and Abby van den Berg cut the top off a maple tree. As researchers at UVM’s Proctor Maple Research Center, they wanted to learn more about sap flow.

Instead, they discovered an entirely new way to make maple syrup. “It’s revolutionary in some ways,” says Perkins ’84 G’88 ’91.

Their new technique uses tightly spaced plantations of chest-high sugar-maple saplings. These could be single stems with a portion—or all—of the crown removed. Or they could be multiple-stemmed maples, where one stem per tree can be cut each year. Either way, the cut stem is covered with a sealed plastic bag. Under the bag, the sap flows out of the stump under vacuum pressure and into a tube. Voilà, huge quantities of sap.

In short, these plantations can allow maple syrup production in a farm field. Typically, a traditional sugarbush produces about forty gallons of maple syrup per acre of forest by tapping, perhaps, eighty mature trees. With this new method, the UVM researchers estimate that producers could get more than four hundred gallons of syrup per acre drawing from about six thousand saplings.

The new technique has the potential to enhance business for existing syrup producers, the researchers think, and defend Vermont’s maple industry from threats that range from climate change to spiking land costs to Asian long-horned beetles.

 “We didn’t set out to develop this system,” says van den Berg ’99 G’00 ’07. “We were looking at ways to improve vacuum systems.” But, during a spring thaw, the tapped tree, from which they had removed the crown, just kept yielding sap under vacuum pressure. And more sap and more sap.

“We got to the point where we should have exhausted any water that was in the tree, but the moisture didn’t drop,” says Perkins. “The only explanation was that we were pulling water out of the ground, right up through and out the stem.” In other words, the cut tree works like a sugar-filled straw stuck in the ground. To get the maple sugar stored in the trunk, just apply suction.

While the cut plantation saplings will regrow branches and leaves from side shoots—and can be used year after year—“the top of the tree is really immaterial for sap flow under vacuum-induced flow,” Perkins says.

“Once we saw that we could get yields without tops it was—wow! —this changes the basic paradigm,” says van den Berg. Large, mature trees are no longer needed to provide the sugar. “It became clear that we could deal with an entirely new framework,” she says.

Intriguing as their findings are, the UVM scientists stress that there is still much to be explored. To date, they’ve made a couple of conference presentations to maple syrup producers and applied for a patent. “This is research,” van den Berg says, “and there’s a lot more research to be done before we know what the implications of this research will be.”

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