Guide

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Pits and mounds: how uprooted trees shape the forest floor

All year

Bumpy woods, where a low mound sits beside a shallow hollow over and over, are the marks of trees uprooted by wind long ago. When a tree blows over its roots rip up a mass of soil and stone and leave a hole, and once the roots rot the soil stays behind as a mound next to the pit.

Why this time of year

These humps and hollows can last for centuries, so they are there in every season. They can be easier to read when the leaves are down and there is no snow.

How to notice it

  1. On a woodland walk, look for a low hump of earth with a hollow right beside it, and then look for the next pair: in some woods they are everywhere.
  2. Stand on the mound and look across the pit. The tree most likely fell toward the mound side, so looking from the mound across the pit, you face the direction the wind came from.
  3. Check the direction of several pairs. If they line up, one storm may have knocked many trees down together, but on a slope trees often fall downhill instead.
  4. Notice where the bumps are missing. Flat, even woods can mean the land was once plowed or cleared, which smoothed old pits and mounds away.

Try this with kids: Find a mound with a hollow beside it and stand on the mound: which way did the tree fall?

Word to know: “Windthrow”: trees blown over by wind, roots and all.

Safety

  • Do not climb on or stand under the upturned roots of a tree that has fallen recently: the root plate can drop back into its hole. Old, rounded, grassy or leaf-covered mounds are the ones to stand on.
  • Where trails are required, look from the trail; do not dig into mounds on conservation land.

Sources

  • harvardforest.fas.harvard.eduHarvard Forest research news 2017: pits and mounds are formed by the uprooting of trees; some mounds remained over 2 m tall 50 years after the 1938 hurricane; farm clearing and logging erased many pits and mounds.
  • harvardforest1.fas.harvard.eduArnoldia 1998: evidence of past storms may persist for as long as a thousand years in the pits and mounds often found in our forests.
  • northernwoodlands.orgNorthern Woodlands 2013: roots ripped from the ground carry soil and stone, excavating a hole; roots and stump decompose leaving a mound; survey of 58 pairs found most faced east, downhill.
  • granthamnh.govGrantham NH interpretive sign: pits and mounds typical of New England forests never plowed; standing on the pillow looking across the cradle you look toward where the wind came from.
  • teagasc.ieTeagasc forestry safety guide: do not walk or work under unstable windblown trees or root plates.

Checked against these sources on October 16, 2026.

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