WINDHAM – Without his vacuum pump system, Mark Cooper, owner of Cooper Maple Products in Windham, says the 2012 maple harvest would be a dud.

“Most definitely it’s helping,” Cooper said last Friday, prior to a week of very warm weather in the Lakes Region. “Everything we have on vacuum is a bit slower but it’s still running. But most everything we have on gravity tubing or just buckets has slowed down to almost a stop, not quite a full stop but just a trickle compared to our vacuum.”

Cooper has one of the largest maple tree harvests in the area, yearly tapping about 1,800 trees in the South Windham and East Windham area. While this season has so far created greater yield than last, it’s a trend he doesn’t expect to continue later in the season due to an early spring. He says the relative early season bounty was only possible due to what maple producers call a vacuum pump system, which sounds elaborate but really isn’t.

This week, Cooper and other maple producers in southern Maine expect thousands of visitors on hand to celebrate Maine Maple Sunday. The annual event celebrates the sap harvest with breakfasts, snacks and tours.

In a normal maple harvest season, the freeze-thaw cycle of a maple tree is made possible by cold nights and warm days that allow trees to build up pressure.

When a tree’s internal pressure exceeds that of the outside air pressure, sap will naturally flow through taps into either buckets or a connected tube system.

When that natural freeze-thaw cycle is interrupted by either warm nights, when temperatures don’t fall below freezing, or cold days, maple producers try to create an area of relatively lower pressure – ideally a vacuum – in the tubing system, which provides conditions conducive to good sap flow.

“It’s become the standard now in the maple syrup industry,” said Kathy Hopkins, extension educator at the University of Maine Cooperative Extension in Somerset County. “But [the pump system] doesn’t actually suck the sap out of the tree. It creates a vacuum so it changes the atmospheric pressure inside the tubing line so that the sap will flow out of the tree. It’s a misconception that it’s pulling it out like sucking something through a straw. It’s not doing that. It’s just changing the atmospheric pressure within the lines.”

Hopkins said the systems are especially helpful on “marginal days, allowing the sap to flow when it might just weep out of a tap into a bucket on those days when the temperature isn’t quite enough of a change between night and day.”

While he’s sold pump systems for several years now, Lyle Merrifield, owner of Merrifield Farm in Gorham, installed a vacuum system this spring for his 400-tree “sugarbush,” as a harvested section of forest is called. Spending an estimated $6,000 on the system, Merrifield considers the purchase an investment.

“The systems have been around for years, probably 35 years, but they’re gaining popularity and the manufacturers are tailoring them a little more to smaller producers like us,” Merrifield said. “They’re not as expensive and they’ve downsized the pumps and made them more user-friendly for a small producer, somebody with 500 to 2,000 taps. A lot of the stuff in the industry is designed for people with 10,000 or 20,000 or 30,000 taps. But manufacturers have realized there’s a big market selling to small producers.”

Cooper, who’s employed pump systems for the last 12 years, says the systems began when dairy farmers converted milking machines for maple production. Since then, they’ve gotten more efficient, he said.

“Back in ’70s, guys used old milking system pumps that would create about 15 inches of mercury of vacuum,” Cooper said, referring to a measure of air pressure. “Now, over the years, technology has advanced with the maple industry and we’re now using a lot of liquid-ring pumps which create high vacuum for 24 hours a day for months on end. And a good tight system can run at 25 inches of vacuum.”

With maple syrup running at about $60 a gallon, getting the most out of a tree without harming the tree for future production is the name of the game for the maple industry.

According to Hopkins at the cooperative extension, scientists at the Proctor Maple Research Center at the University of Vermont have run extensive tests on vacuum pump systems trying to find the point at which a system could be harmful. And what they’re finding is that the trees really don’t have a limit, she said.

“It’s not really either good or bad for the tree,” Hopkins said. “I suppose there’s an upper limit somewhere in a pure scientific sense, but in practical reality they can’t find any impact on the tree from any levels of pressure or vacuum.”

While costly up front, pumps also require some ongoing power source to operate. And with gasoline skyrocketing once again, and a farmer’s profit margin of utmost consideration, the pump system is only useful for producers of a certain volume. For small producers, a new invention may come in handy, though. Hopkins says a Proctor scientist experimented with a new tubing design last season that could make the costly pumps obsolete even for large producers.

The experiment piggybacked on the concept of modern water systems, through which water flows from large water mains into progressively smaller diameter pipes, gaining pressure as it goes. When it reaches a household tap, the water pressure is comparatively high.

“So, the idea was, what if you could do that to the tree? A Proctor scientist, Tim Wilmot, took various sizes of tubing to change the pressure so the sap would flow out of the tree,” Hopkins said. “He started with one size of tubing, and narrowed it down with little inserts and that change in diameter of the tubing led to an increased flow rate. So, in essence, he created a vacuum mechanically just by changing the size of the tubing, which I thought was pretty interesting and innovative.”

And, Hopkins added, the system is especially helpful for a small operation, “which doesn’t want to get into the cost of setting up a pump and power source.”

But, like Cooper says, even technology can’t change Mother Nature when she’s made up her mind. While the pumps can mimic lower atmospheric pressure outside a tree, it can only so until the maple tree starts producing leaves, a process that Cooper has already seen on trees in full sun.

“Yes, if it stays warm long enough even a vacuum doesn’t help,” Cooper said. “These excessively warm temperatures will push the trees to bud out a lot sooner, which will definitely end our season. Once the buds come out, that’s the end of that. And this year, it is happening two weeks, perhaps more, earlier than usual.”

Mark Cooper, owner of Cooper Maple Products on Chute Road in Windham, inserts a tap into one of his 1,800 maple trees. Without the help of a vacuum pump system, which helps draw sap from a tree, Cooper said, the unusually warm weather of late would have made for low syrup yield. (Staff photos by John Balentine)
Sitting atop a sap collection tank, a vacuum pump system is the key to making an average season better. The system, located in woods owned by Mark Cooper of Cooper Maple Products in South Windham, works to increase sap yield by reducing air pressure in the tubing. The system is especially helpful on marginal days when a tree’s internal pressure isn’t much different from that of the surrounding air. The lower pressure in the tubes teases a tree into pushing out sap by the process of osmosis.
Lyle Merrifield, of 195 North Gorham Road in Gorham, has a well-stocked shop for Maine Maple Sunday. And while the warm weather has slowed sap production, he’s saved enough to fire up the boiler for his visitors to send them home with the smell of freshly made syrup lingering. (Photo by Rich Obrey)