How warming winter temperatures impact maple syrup production in Pennsylvania

Dennis Snook, owner of Paddy Mountain Sugar Shack in Millmont, Union County, usually marks Valentine’s Day as the start day to tap his 375 sugar maple trees. But this year, he tapped on Jan. 27.

Just east of Woodward along state Route 45, Snook’s midsize operation produces about 75 gallons of maple syrup annually, which he sells out of his sugar shack to benefit charity. But with warmer than average winters, that may not always be possible.

“In nearly all states east of the Rockies, winter is the fastest warming season,” said Jon Nese, teaching professor of meteorology at Penn State and host of Penn State’s “Weather Whys?” show, which airs on WPSU. “And according to the Intergovernmental Panel on Climate Change, which is the gold standard for synthesizing research on climate change, most of this warming is attributable to human activity.”

Winter temperatures in Pennsylvania have warmed, on average, five degrees since 1960, according to Nese. And last year was the warmest year on record for State College, Dubois, Williamsport and Bradford, with a tie for warmest in Harrisburg.

“When you look at long-term temperature trends, the last 50 to 60 years show the biggest warming trend, where every decade is warmer than the previous decade,” Nese said.

Maple syrup producers rely on freezing nights and sunny, thawing days for sap to flow, according to Penn State Extension Forest Resources Educator Scott Weikert. Traditionally, syrup producers in Pennsylvania would tap in mid- to late-February, production would peak in mid-March, and the season would end in early April.

“The season has been starting earlier, I would say, in the last five to 10 years,” Weikert said. “If producers don’t get their taps out in January now, they might miss several sap runs.”

But there is a dilemma with earlier tapping, Weikert explained. With warmer daytime temperatures, natural yeast and bacteria in the air sets into the drill holes and multiplies, causing the hole to dry out and close before a full sap run can be completed, leading to lower sap yields.

“So, if you tap early, your season may also end early,” Weikert said.

Using sanitized equipment and following good sanitation procedures around tap holes can cut down on bacteria and yeast growth, Weikert explained, which he said is increasingly important during milder winters.

The other problem is storing the sap: it spoils if it gets too warm. With the exception of smaller hobbyists who can store a few gallons of sap in a fridge, most midsize producers, like Snook, store their sap outdoors. And due to the size and capacity of their equipment, midsize producers need to collect about 100 gallons of sap before they can boil it into syrup.

“If the air temperatures get above 40 or 45 degrees, that natural yeast and bacteria in the sap builds up a lot faster, causing it to spoil before producers can get a chance to boil it down into syrup,” Weikert said.

Snook said that though this winter hasn’t been terrible for collecting the sap, it is a challenge to store and boil the syrup during warmer periods.

“Toward the end of the season, the sap will get yellowish, the tap holes heal, and the amount of sap you get will go down,” Snook said. “This year, if we can make it to the middle of March, we’d be doing great; if we make it to the end of March, that would be excellent. There comes a time to throw in the towel.”

Snook is part of the River Valley Maple Producers Association, one of six associations that make up the Pennsylvania Maple Syrup Producers Council. He said that he and other members struggle with the question of how to stay in the game as long as possible.

“That’s been one of our questions to hash back and forth: how can we get the most that we can, while we can, in this area?” Snook said.

Snook was sure to point out, however, that his location in West Union County has always been challenging due to its location further south in comparison to the majority of Pennsylvanian syrup producers, who are located north of Interstate 80.

“You know, it’s a challenge, but I’m hesitant to say for sure that it’s getting worse,” Snook said. “I don’t think that’s the total answer yet.”

A complex issue, one season’s temperature fluctuations cannot be attributed directly to climate change, according to Nese.

“What’s more proper to say is that governing the climate right now is this overall warming tendency, which loads the dice toward warmer than average winters,” Nese said. “Weather and climate have a natural variability to them, and I suspect that one of the upcoming winters may turn out to be a colder than average winter. But right now, the dice are not loaded that way.”