Community find

Chaga mushroom

Inonotus obliquus

Group

Canker / Hymenochaetoid fungus

Spore print

White to pale yellow (rarely observed since spores are produced in concealed, short-lived sexual fruiting bodies beneath bark).

Size

Sclerotium masses typically range from 10 to 40 cm (4 to 16 in) across.

Season

Perennial; visible year-round on host trees.

Habitat

Parasitic on living birch trees (Betula spp.), occasionally found on beech, alder, or oak.

Distribution

Circumboreal in the Northern Hemisphere, prominent in boreal forests of Russia, Northern Europe, Canada, and the Northern United States.

Key characteristics

Irregular, charcoal-black cracked exterior resembling burned charcoal; golden-brown to dark orange interior with a hard, woody, fibrous texture.

Fruiting body

The visible growth is actually a sterile mycelial mass or sclerotium/canker, displaying a deeply cracked, blackened outer surface caused by high melanin levels and a corky, golden-brown interior. The true fertile fruiting body develops rarely under bark after the host tree dies.

How to recognise it

Look for charcoal-like black crust with a rusty yellowish-brown or golden interior growing specifically from living birch trees.

Look-alikes

Tree burls (growth swellings without the charcoal-like crust or brownish interior) and Phellinus species.

Ecological role

Parasitic, causing white rot in host trees, eventually saprophytic after tree death.

Notes

The dense black exterior of Chaga is caused by extremely high concentrations of melanin. Traditionally, dried pieces of the sclerotium were used as a tinder to catch sparks for fire-starting due to how slowly it smolders.