Chaga

Description

The chaga fungus (Inonotus obliquus) is not a typical mushroom with a cap, but a black, lumpy, cracked growth on the trunk of a living tree, looking like a piece of charred wood or cinder. The growth can be several dozen centimetres across, and its interior is reddish-brown and hard. The true fruiting body develops only under the bark after the tree dies, and is almost never seen.

It grows mainly on birches, less often on other broadleaf trees, in forests and parks. In Poland it is rare and covered by partial species protection.

It is not an edible fungus. Chaga is collected as a raw material for infusions, but because of the partial protection you must check the current regulations before collecting. The parasite weakens and usually kills the tree.

Identification features

Cap

It produces two forms of fruiting body. The asexual form (anamorph, chaga, sclerotium) is a perennial, lumpy, warty, cracked growth, firmly fused with the tree and attached sideways, of irregular shape, up to 50 cm in diameter (descriptions also give a growth of 10–25 cm and a crust of 5–50 cm). The outer layer is dry, hard, flaking, charred, cinder-like, matt, blackish-brown to blackish-navy, with a reddish-brown tint in fresh cracks. The sexual form (teleomorph) is spread out (resupinate), annual, grows under the bark after the tree dies, 5–10 mm thick, initially fleshy-leathery, then corky and brittle; rarely seen.

Hymenophore (underside of the cap)

Only in the sexual fruiting body: poroid, one layer of tubes up to 10 mm long, arranged obliquely to the substrate; pores round or oval, 0.1–0.3 mm in diameter, covered with a whitish or greyish bloom. No stem.

Stem

No stem.

Flesh

The interior of the growth is reddish-brown and hard; smell and taste — no data. The flesh should not be tasted.

Spore print and spores

Spore print colour: no data. Basidiospores narrowly ellipsoid, colourless, smooth, 8–10 × 5–7.5 µm.

Habitat and distribution

Ecology. A parasite of broadleaf trees, causing intense white rot of wood; it enters the tree through wounds (including badly healed branch stubs) and develops over many years (according to some descriptions 10–80 years), usually leading to the death of the host. Grows mainly on silver birch and aspen, also on alder, maple, hornbeam, beech, rowan, elm; in Poland primarily on birches. In forests, less often in parks.

Distribution. The whole Northern Hemisphere, especially the circumboreal zone in birch forests. Rare in Poland, although many sites have been reported; on the Red List of Plants and Fungi of Poland it has the status R (potentially threatened because of its limited range and small habitat areas, 2006). Covered by partial species protection (Dz.U. 2014 item 1408).

Fruiting. Chaga is perennial and visible all year round; the sexual fruiting body forms under the bark after the tree dies, with no defined season.

What can it be confused with?

• Apiosporina morbosa, Diplodia tumefaciens, Echinodontium tinctorium, Fulvifomes spp., Fomitiporia spp. — Mentioned as similar; detailed differences — no data. Chaga is distinguished by a black, charred, cracked growth on a living tree (usually a birch) with a reddish-brown interior.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• The name “chaga” comes from the Russian ча́га, borrowed from the Komi language (tšak, “mushroom”).
• A lit chaga can smoulder for several hours, so the peoples of northern Eurasia and North America formerly used it to carry fire; the Potawatomi call it shkitagen.
• The black colour of the growth results from a large amount of melanin; the growth is a sclerotium (compacted mycelium), not a sexual fruiting body.
• According to legend, the Rus prince Vladimir Monomakh was cured of lip cancer with chaga (a legend, unconfirmed).