Guide

Look closerFungi

Old man's beard lichen and its stretchy inner cord

All year

Old man's beard (Usnea) is a pale gray-green, hair-like lichen that hangs or tufts from twigs and branches. Air pollution once wiped it out near the city and it is only beginning to come back, so treat a sighting as a small win.

Why this time of year

Lichens are on branches in every season. It is a good walk-with-a-hand-lens find any month, with no weather needed.

How to notice it

  1. Scan tree branches and any fresh fallen twigs for pale gray-green, hair-like tufts or short hanging strands. Wet woods and old trees are the best bets.
  2. If you spot something, look first at lichen already on the ground. Do not pull any off a living branch.
  3. On a fallen piece, gently stretch one strand. Usnea has a stretchy cord inside the branch, so it gives a little before it parts.
  4. Note where you found it. Usnea is sensitive to air pollution, so seeing it is a good sign for the air, though not a measurement.

Try this with kids: Can you find a lichen that looks like tiny gray-green hair, and gently stretch a fallen piece to feel if it has a stretchy middle?

Word to know: “Lichen”: a partnership between a fungus and an alga that grows on bark and rock.

Safety

  • Pick up only fallen pieces; leave lichen on living trees alone.
  • Do not eat lichens.

Sources

  • mdc.mo.govState agency field guide (primary-ish, Missouri). 'flexible, elastic, cordlike central axis within the branches (try stretching one of the branches)'; 'recently fallen branches lying on the ground may have beard lichens attached'; 'Air pollution harms many lichens.'
  • massaudubon.orgMass Audubon breeding bird atlas: 'The Usnea lichens on which this species depend are highly sensitive to airborne contaminants'; lichen diminished early 20th century; parulas nested only 'in wet forests where there was an abundance of Old Man's Beard lichen' (Cape Cod sites).
  • arboretum.harvard.eduHarvard Arnold Arboretum: 'These lichens disappeared from Boston as a result of pollution, but are beginning to show up again.' Usnea recorded in NYC for first time in nearly 200 years. Shows scarcity near Boston metro. The refute pass confirmed from page context that 'these lichens' is the Usnea found on a red buckeye ('The most exciting find ... was a species of Usnea, aka old man's beard').
  • nps.govUS National Park Service: lichen species present 'can tell us a lot about air quality'; sensitive species may be replaced by tolerant ones; reflects past and present air, so absence is not proof.

Checked against these sources on October 13, 2026.

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