Community find

Chaga

Inonotus obliquus

Group

polypore/conk

Spore print

White to pale yellow (from the true fruiting body, not the sterile conk).

Size

Sclerotium can range from 10 to 40 cm (4-16 inches) in diameter.

Season

Visible year-round; harvests typically occur in winter when temperatures are below freezing.

Habitat

Found almost exclusively on birch trees (Betula species), occasionally on beech or alder.

Distribution

Common in circumboreal regions of the Northern Hemisphere, including Russia, Northern Europe, Canada, and the Northern United States.

Key characteristics

Sterile conk; rough, cracked, blackish exterior resembling burnt charcoal; golden-brown to orange interior; hard and woody texture.

Fruiting body

The visible part is a sterile sclerotium (a mass of mycelium), not a true fruiting body. The true fruiting body is rare and grows under the bark once the tree dies.

How to recognise it

Look for a black, charcoal-like protrusion on birch trees with a contrasting bright orange-brown interior when chipped or broken.

Look-alikes

Phellinus igniarius (False Tinder Fungus) and certain burls (abnormal wood growth), but both lack the distinct golden-orange crumbly interior of Chaga.

Ecological role

Parasitic, eventually causing white heart rot in the host tree, and saprophytic after the tree dies.

Notes

The black exterior is due to a high concentration of melanin. Unlike most mushrooms that produce fruit yearly, a single Chaga sterile conk can grow for decades on its host tree.