Inedible
Tinder Conk
Fomes fomentarius
Also on birch, but gray, hoof-shaped, ridged, very hard and perennial, with a brownish pore surface.
Birch Polypore
Fomitopsis betulina
Inedible
Also called razor strop fungus, birch bracket, birch conk.
The birch polypore is a smooth, white to tan bracket that grows only on dead and dying birch trees. Its rounded, rolled edge and white underside make it easy to spot. Ötzi the Iceman carried pieces of it, and it was once used to strop razors.
The tell
A smooth, pale, kidney-shaped bracket that grows only on birch, with a rolled edge overhanging white pores.
Field marks
What to look at
Cap, underside and stem show in a photo. The spore print does not, and it is often the deciding check.
- Cap
- Kidney- to hoof-shaped bracket, smooth, white to pale tan or grayish brown, with a thin skin that cracks with age. The thick edge rolls down and overhangs the pore surface.
- Underside
- White pore surface with tiny pores, browning with age.
- Stem
- None, or a short knob where the bracket attaches to the trunk.
- Flesh
- Thick, white, firm and rubbery to corky. Smell pleasant.
- Spore print
- White.
- Size
- Bracket 2 to 10 inches (5 to 25 cm) wide and 1 to 2 1/2 inches (2.5 to 6 cm) thick.
Where and when
Where and when it grows
- Habitat
- Northern forests and anywhere birches grow, on standing dead trunks, snags and fallen logs.
- Grows on
- Dead and dying birch only.
- Season
- Grows in summer and fall; old brackets persist through winter.
- Range
- Across northern North America wherever birches grow.
Lookalikes
What the birch polypore gets confused with
Each card says how to tell the two apart.
InedibleArtist's Conk
Ganoderma applanatum
A flat, dull brown to gray bracket on many hardwoods, whose white underside bruises dark brown when scratched.
Inedible, used in teasChaga
Inonotus obliquus
Also on birch, but a black, cracked, charcoal-like mass with no bracket shape and no pores.
Edibility
What the field guides say
Inedible
Field guides list the birch polypore as inedible because it is tough and bitter. It is not known to be toxic. Pieces were found with Ötzi, the 5,300-year-old Iceman discovered in the Alps in 1991, and strips of its dried flesh were once used to strop razors.
This page states what field guides record. It is not advice to eat, taste or handle anything, and a photo cannot settle edibility. If someone has eaten a wild mushroom that may be toxic, call poison control (1-800-222-1222 in the US) right away, before symptoms start: the deadliest species act hours later.
FAQ
Questions about the birch polypore
Is birch polypore edible?
Field guides list it as inedible because it is tough and bitter. It is not known to be poisonous.
Why is birch polypore called razor strop fungus?
Its dried flesh is smooth and leathery, and it was cut into strips to sharpen and polish razor blades.
Does birch polypore only grow on birch?
Yes. It grows only on dead and dying birch, so the tree is a reliable clue.
Sources
Where these facts come from
- Fomitopsis betulina
MushroomExpert.com
- Fomitopsis betulina
Fungi Growing on Wood, Gary Emberger (MushroomExpert.com)
- Fomitopsis betulina
Index Fungorum
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