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Pale birch polypore bracket on a birch trunk
Not a food mushroombeginner-friendly group

Birch Polypore

Fomitopsis betulina / Razor strop fungus

A smooth, pale, kidney-shaped bracket that grows only on birch, carried by Ötzi the Iceman 5,300 years ago.

Photo: Марина Давлетшина, CC BY
Compiled by Mushroom Forage Map field deskExpert review pendingContent checked
Identification warning

Tough and bitter; not a food mushroom.

Season
Late summer to autumn; old brackets persist
Habitat
Dead and dying birch
Underside
White pore surface
Spore evidence
White

Where it grows

Tracked records and known growing zone

Explore on the field map
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Squares: where people recorded it, brighter where more people did
Verified records
39,843
People who recorded it
18,678
Most records (northern hemisphere)
Apr–May, Sep–Nov
Records span
1981–2026

Research-grade iNaturalist records, snapshot Aug 27, 2026. The growing zone combines areas where different people have repeatedly verified it. Records show where people looked and found it, not current abundance or permission to gather.

Observation season

When field records occur

Choose a hemisphere · All recorded years; not a current forecast.

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Compare before concluding

Lookalikes to rule out

Tinder fungus is gray, hoof-shaped, and hard.

Chaga

harmless

Chaga is a black, cracked canker, not a bracket.

Other white brackets

harmless

Few white brackets have the rolled margin and birch-only habit.

Identification

The bracket is kidney-shaped to rounded, smooth, and white to pale tan, with a margin that rolls under the white pore surface. It grows only on birch, often high on dead trunks.

Uses and ecology

Birch polypore causes brown rot in dead birch and speeds their decay. Its tough surface was once used to strop razors, and it has been used as tinder and in traditional remedies.

Memorable fact

Ötzi, the 5,300-year-old Iceman found in the Alps, carried pieces of birch polypore threaded on a leather strip.

Sources

Never eat a mushroom from this page alone

Confirm identity using the whole specimen, multiple reputable sources, and a qualified local expert. Identified edible species still require appropriate preparation. Cooking does not make a poisonous mushroom safe.

Safety and poison response
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