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How freezing nights and thawing days make maple sap run

February to March

Maple trees push sap out of wounds on days when a freezing night gives way to a thaw, and in Massachusetts that typically happens from about mid-February to mid-March. Sometimes the sap drips off a broken twig and freezes into an icicle made of maple sap.

Why this time of year

Mass Audubon puts Massachusetts sap runs typically from mid-February to mid-March, when nights drop to 25 F or below and days warm to 40 F or above, and says the schedule has been getting more erratic. Repeated freezing and thawing builds pressure inside sugar and red maples, and that pressure pushes sap out where the bark is broken.

How to notice it

  1. Pick a cold morning after a day that warmed above 40 F, when the night dropped to about 25 F or below.
  2. Find a maple you can walk up to, in your own yard or along a street, and look at the ends of its lower twigs, especially ones already snapped by wind or ice.
  3. Look for a small icicle hanging from a broken twig tip, on a day with no snow or ice on the branches above it. It may be frozen sap, which Mass Audubon calls a sapsicle.
  4. Leave the twigs as they are. Sap only runs where the tree is already wounded, so just look and count.

Try this with kids: How many maple twig icicles can you count without touching the tree?

Word to know: “Sap”: the watery sugar solution that moves up inside a maple in late winter, about 2 percent sugar in a sugar maple.

Sources

  • massaudubon.orgPrimary (Mass Audubon). Quote: 'Sap runs typically occur in Massachusetts from mid-February to mid-March.' Nights 'fall below 25 degrees Fahrenheit', days 'warm to at least 40 degrees Fahrenheit'. 'This oscillation of freezing and thawing triggers sap flow.' Sugar maple sap sugar 'typically around 2%, but can vary from tree to tree and according to season.' 'To produce one gallon of syrup, 40-50 gallons of raw sugar maple sap needs to be collected.' Page does not mention sap icicles or broken twigs. Read 2026-11-06; evergreen activity page, not a rotating feed.
  • blogs.massaudubon.orgPrimary (Mass Audubon blog post 'Much Ado About Maple', 2013-02-19; the canonical URL blogs.massaudubon.org/yourgreatoutdoors/much-ado-about-maple now 301-redirects to massaudubon.org/news, so the wp-json copy is the one that opens). Carries the sap icicle: 'sapsicles,' 'the icicles of frozen maple sap that form from the end of a broken twig.' Also: 'The normal tapping time in Massachusetts is mid-February to mid-March.' 'Sap will run when nights are cold, 25 degrees F or below, and days are warm, 40 degrees F or above.' Its tasting line is a historical guess about Native Americans, not advice to readers.
  • massaudubon.orgPrimary (Mass Audubon Ipswich River sanctuary news, 2024-12-19). Season: 'typically begins in February and continues into the first weeks of March.' Ratio: 'It takes 40 gallons of tree sap to make just one gallon of syrup.' Backs the February-March window for eastern Massachusetts (North Shore).
  • arxiv.orgPrimary research (Zarrinderakht, Konrad, Wilmot, Perkins, van den Berg, Stockie; Perkins and van den Berg are UVM Proctor Maple Research Center). Sugar and red maple 'generate high positive stem pressure in response to repeated freeze-thaw cycles.' Abstract also says the literature holds 'various competing hypotheses' on the mechanism, so the card says pressure builds and does not explain how.
  • ag.ndsu.eduExtension (NDSU, forester Joe Zeleznik, 2022-04-05). How a tree icicle forms: 'Sap must leak out of a wound in the branch' and the air must be cold enough 'to freeze that sap before it drips to the ground.' 'Some type of wound is always associated with a birch-cicle.' Records 'A lone icicle was hanging from a branch on a maple tree.' Sap flow: 'Nighttime temperatures must be below freezing and daytime temperatures have to be above freezing.' North Dakota, so used for the mechanism only, not for timing.
  • yardandgarden.extension.iastate.eduExtension (Iowa State). Maples 'bleed' heavily when cut in late winter or early spring: 'Some tree species, such as maple, birch, and elm, "bleed" heavily when pruned in late winter or early spring.' 'the loss of sap does not harm the trees.' Backs the claim that sap leaves through wounds in this season, and that a dripping wound is not something to worry about.
  • cincynature.orgSecondary (Cincinnati Nature Center blog, Dylan Bean, 2021-02-17), an Ohio nature center outside the preferred roster. Second source for the icicle: 'sapsicles' 'hanging from broken twigs of sugar maple trees'. Calls them 'tasty', but the card does not suggest tasting, because this is not a preferred-roster source and it does not say whose tree.

Checked against these sources on November 6, 2026.

In the guide for February, March

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