What do weather conditions have to do with maple syrup harvesting?

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What do weather conditions have to do with maple syrup harvesting?

Weather is a crucial factor for a good harvest of maple syrup. Tapping trees occurs in late winter and early spring. In Wisconsin, March is a prime month for tapping sugar maple trees as that is when the sap is sweetest. Only about 2 percent of the sap is sugar, so it needs to be boiled down to remove the water and increase the sugar concentration.

Good weather for sap production are night temperatures in the 20s F and sunny days with temperatures in the 40s F. This alternate freezing and thawing temperature cycle (which can also cause potholes on roads) causes the pressure changes inside the tree that makes the sap flow. If the nighttime temperatures are too cold, it takes a longer time for the sap to warm up and ‘run’ in the daytime. If the temperatures are very cold, the sap may not run at all.

Tree species have adapted to different climate conditions, particularly temperature and moisture. Trees have also adapted to natural threats, such as fires, insects, droughts, and windstorms. Sugar maple trees don’t live in regions where summer temperatures frequently reach 100 F or where the winter temperatures regularly drop below 0 F. In the United States, the best climate conditions for sugar maple trees are found in the northeastern and north central regions. In the near future, these forests may face environmental changes associated with global climate change.

Steven A. Ackerman and Jonathan Martin are professors in the Department of Atmospheric and Oceanic Sciences at UW-Madison, are guests on the Larry Meiller‘s WHA-AM radio show the last Monday of each month at 11:45 a.m.