A friend of the magazine contacted me recently with a deceptively simple question: how do I know when to start tapping my maple trees? The literal answer, “whenever you can take time off from work”, is not very technically illuminating.
From a scientific perspective, there is no definitive answer to this question, as the two major players in this story, besides the sugarmaker and the tree, are bacteria and temperature – two notoriously fickle elements.
A taphole is an open wound, which means there’s no way to shield it from naturally occurring bacteria, yeasts, and fungi. These microorganisms take up residence in a tap hole, and they eventually form a gummy barrier that blocks the sap from coming out. Temperature comes into play because these microorganisms are enabled by heat. Like many living things, they’re just not very prolific in the cold.
So. Let’s say weather played by the rules, and outside temperatures got cold in December and stayed cold through February, and on March 1, right on schedule, daytime temps crept up into the 40s and went back down to the high 20s at night. And these temps rose incrementally through mid-April, just like we’re told they did in the good old days. If weather behaved predictably like this, then in theory we could tap trees in December and have productive tapholes right through mid-April. Experiments at the Proctor Maple Research Center in Vermont and other maple research organizations bear this out, and large-scale sugaring operations with tens of thousands of taps start drilling in December and January every year – they have to.
What complicates things is that weather doesn’t behave rationally and never has, which gives smaller scale operators with more tapping flexibility something to agonize over. Bacterial growth is stimulated by warm spikes in the weather, so there is some risk to tapping early. While research shows a negligible flow difference between January-drilled holes and March-drilled holes in the cooler parts of March (35 to 40 degree runs), that changes when the temperature spikes above 50 degrees. Then, early-drilled holes begin to show the effects of a burgeoning bacteria population and they yield less sap than newer holes.
So it’s a big guessing game. At my own sugarbush in southern Vermont, we’ve had years where I’ve felt we’ve tapped too early. We struggled, fighting snow and ice, to boil low-sugar content sap through warm spells in early February, then seemed to get passed, production wise, by more patient sugarmakers who were still making syrup when we weren’t in April. Of course, there have probably been more years where it’s worked the other way, when jackrabbits like us were banking barrels of nice early-season fancy, wondering what the March-tapping turtles were waiting for.
Of course my own experiences are anecdotal and not at all scientific. To read some objective science on the subject, check out a piece that Proctor’s Tim Wilmot wrote on early tapping in the Maple Syrup Digest.
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