Community find

Chaga mushroom

Inonotus obliquus

Group

polypore

Spore print

Brown (rarely observed as spores are produced by the hidden fertile body).

Size

Sclerotium typically ranges from 10 to 40 cm in diameter, though it can grow larger.

Season

Can be found year-round, but is most visible and accessible in winter when foliage is gone.

Habitat

Primarily grows on birch trees (Betula genus), though occasionally found on alder, beech, or oak. It develops on the trunk as a sterile conk.

Distribution

Circumboreal distribution, common in the Northern Hemisphere including Russia, Korea, Eastern and Northern Europe, Canada, and Northern USA.

Key characteristics

Rough, blackened, coal-like sclerotium with a bright golden-brown or orange interior. The exterior surface is cracked and resembles burnt charcoal. It is hard and woody in texture.

Fruiting body

The visible part is a sterile sclerotium (a mass of mycelium), not the actual fruiting body. It lacks a cap, stem, or gills. The true fertile fruiting body develops under the bark of dead trees and is rarely seen.

How to recognise it

Look for a charcoal-black, deeply cracked growth on birch. Break a small piece to confirm the distinct cinnamon or golden-orange interior which contrasts sharply with the black exterior.

Look-alikes

Black cherry burl (tree growth), Birch canker, or Phellinus igniarius (False tinder fungus) which has a more distinct shelf-like bracket shape.

Ecological role

Parasitic on living trees, eventually causing white rot in the heartwood. It can continue to act as a saprotroph after the host tree dies.

Notes

The 'black' exterior is actually an exceptionally high concentration of melanin. It takes many years (typically 10-20) for the sterile conk to reach a large size. In some cultures, it has been used as a natural dye or as tinder for starting fires.