Commonly known as chaga mushroom (a Latinisation of the Russian term ‘чага’), is a fungus in the family Hymenochaetaceae. It is parasitic on birch and other trees. The sterile conk is irregularly formed and has the appearance of burnt charcoal. It is not the fruiting body of the fungus, but a sclerotia or mass of mycelium, mostly black because of the presence of massive amounts of melanin. The fertile fruiting body can be found very rarely as a resupinate (crustose) fungus on or near the clinker, usually appearing after the host tree is dead. I. obliquus grows in birch forests of Russia, Korea, Eastern and Northern Europe, northern areas of the United States, in the North Carolina mountains and in Canada.
Chaga has been used as a folk remedy in Russia and other North-European countries for centuries and it featured in Aleksandr Solzhenitsyn’s 1967 novel Cancer Ward Though, according to the Memorial Sloan Kettering Cancer Center, “no clinical trials have been conducted to assess chaga’s safety and efficacy for disease prevention or for the treatment of cancer, cardiovascular disease, or diabetes”.