Major Groups > Polypores > Inonotus obliquus


Inonotus obliquus

[ Basidiomycota > Hymenochaetales > Hymenochaetaceae > Inonotus . . . ]

by Michael Kuo

Yuck. This unattractive fungus is a parasite on paper birch throughout the tree's range in North America. Inonotus obliquus is usually found on standing trees, looking like a large lump of blackened, crusty material, reminiscent of charcoal, thrusting itself through the tree's bark. This stage of the fungus, which is described and illustrated here, is asexual (officially it's called a "sclerotium"); the later, sexual stage of Inonotus obliquus appears after the death of the tree, underneath the bark, appearing like a spreading patch of whitish-then-brown, poroid material. The sexual stage is rarely seen, since it occurs under the bark.


Ecology: Parasitic on paper birch and, after the death of the tree, saprobic; causing a white rot; found year-round, but growing in summer and fall; widely distributed in northern North America, throughout the range of paper birch. The illustrated and described collections are from Michigan.

Fruiting Body (Sclerotium): Up to 30 cm across and 30 cm high; irregular in outline; erupting through the bark and creating a mass that protrudes 2-5 cm at first but becomes concave over time; surface black, hard, and broken into charcoal-like cubes; dry; exposed flesh orange-brown.

Flesh: Tough; woody; bright orange-brown.

Chemical Reactions: KOH instantly black on flesh.

Microscopic Features: Hyphal system monomitic; hyphae 2.5-5 µ wide, moderately thick-walled, brown in KOH, smooth. Clamp connections not found. Microscopic features of the sexual stage, which I have not studied, are reported to include short, fusiform setae and ellipsoid spores measuring 8-10 x 5-7.5 µ.

REFERENCES: (Acharius ex. Persoon, 1801) Pilát, 1942. (Fries, 1821; Saccardo, 1888; Breitenbach & Kränzlin, 1986; Gilbertson & Ryvarden, 1986; Phillips, 1991/2005; Lincoff, 1992; McNeil, 2006.) Herb. Kuo 05241406, 05251401.

Further Online Information:

Inonotus obliquus at Roger's Mushrooms


Inonotus obliquus

Inonotus obliquus

Inonotus obliquus

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Kuo, M. (2016, January). Inonotus obliquus. Retrieved from the MushroomExpert.Com Web site: