What we call “Chaga (a Latinisation of the Russian word чага) is the dense black mass that can be seen on the exterior of birch trees infected with the fungus “Inonotus obliquus” Chaga It’s not a mushroom (fruiting body) but a dense sterile mass of decayed bits of birch tissue with mycelia incorporated. Chaga grows in very cold climates, such as Canada , Alaska ,Northern Europe, Siberia, Russia, Korea… But still commonly referred as as Chaga Mushroom