Hoping For A Syrup-y Spring

Sugar Maple trees (Acer saccharum) are the state tree of Wisconsin, but many Wisconsinites don’t know much about this wonderful and culturally important tree. Sugar Maples can be found through much of the  northeastern United States. The wood is heavy, strong, and attractive, so it is often used for furniture and interior furnishing, but the better known use of sugar maple trees is for maple syrup!

MN Arboretum depiction of sugar maple tree range (dots) vs. commercial syrup production range (shaded)

gRmHy9NIn cold climates, these trees store starch in their trunks and roots to sustain themselves through the winter. The starch is then converted to sugar, and six to eight weeks before mature maple trees bud in the spring, this sugary mixture called sap can be collected by maple syrup producers. As spring temperatures drop below freezing and water in the tree cells freezes, this creates suction and pulls sap up from the roots. Then, when temperatures rise above freezing the water melts and builds pressure in these cells. If we insert a tap into the tree trunk in the spring, this pressure causes sap to flow out of the tree. This freezing and thawing cycle is vital to the production of maple syrup, and it’s the reason that maple syrup can only be produced in the northern area of the Sugar Maple tree range.


Some Tapping Ground Rules: 

  • Sugar maples can be tapped at 40 years of age and will yield sap for 100 years or more!
  • A tree large enough to be tapped can be re-tapped year after year — you just need to drill a new hole each tap season.
  • When producers follow tapping guidelines, the tree is not damaged at all!
  • According to estimates, only 10% or less of the tree’s sugar is removed during tapping — plenty left over to grow for the spring!

Syrup can be harvested as long as this freeze & thaw cycle builds pressure and causes the sap to flow. However, once the first buds appear on the tree the taps are removed to allow the sap to support new spring growth! The sap also begins to taste bitter at this point and doesn’t make very tasty syrup. In fact, syrup can have different colors and flavors depending on when the sap is harvested throughout the season. Sap collected early in spring will make a light colored syrup, and it’ll get darker as the season progresses. Nothing is added to the sap to make the final syrup-y product, but extra water must be boiled off.


Did you know?

  • A gallon of maple syrup weighs about 11 pounds, compared to 8 pounds for a gallon of water.
  • Each tap can yield 10+ gallons of sap per season on a typical system.
  • It takes 40 gallons of maple sap to make one gallon of pure maple syrup!

Many of the syrup brands you find in the grocery store aren’t “true” maple syrup but rather a combination of high fructose corn syrup, coloring, and artificial flavors. This syrup will likely always be available, but the real Wisconsin maple syrup that so many people love might be in danger! As climate changes brings milder winters, this crucial freeze and thaw cycle has been happening later and later (or sometimes for too short of a time). For example, in 2012 unusually warm weather caused maple trees to bud early, ruining the sap flavor and ending the maple syrup season after only 1 day. When this happens or if maple syrup producers incorrectly predict the ideal time to tap their trees syrup, prices can skyrocket.

If this trend continues, climate conditions may prevent Wisconsin from being a syrup producing state. The loss of this industry in Wisconsin would be tragic since the syrup industry in Wisconsin ranks 4th in in the nation (behind Vermont, New York, and Maine), and Native Americans in this region have been collecting and trading maple syrup long before colonists arrived.

To learn more, visit the Aldo Leopold Nature Center this month to see our tapped sugarbush, attend Maple Syrup Fest, spring into phenology, explore our Climate Education Center, or try our Digital Docent self-guided tour to learn how climate change is affecting sugar maples and other local species.

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