About this fungus
Chaga is a fungus in the Hymenochaetaceae family. Its habitat and field characteristics are summarised below.
The familiar Chaga conk is a hard, irregular charcoal-black mass breaking through the bark of a living tree. Its cracked sterile crust covers a corky orange-brown interior. It is not the fungus's ordinary spore-producing bracket.
What to check
Confirm a living birch or another documented host, a deeply cracked black exterior and orange-brown tissue beneath. Birch burls, old wounds, fire scars and other canker fungi can all make dark swellings, so shape and colour alone are not enough. The rare fertile stage forms beneath bark, generally after the host or affected trunk section dies, and looks unlike the black conk.
Habitat and range
Parasitic mainly on living birches across cool northern regions of Europe, Asia and North America, with occasional records from other broad-leaved hosts. The visible sterile conk may persist for years while the fungus causes internal white rot.
Food safety
Not generally used as food.
Photographs
Tocekas / CC BY-SA 3.0