Annls mycol. 39(1): 47. 1941.
Common Name: kurotake
Synonym: Polyporus griseus Peck
Misapplied names: Boletopsis subsquamosa (L.) Kotl.& Pouz.; Boletopsis leucomelaena (Pers.) Fayod
Cap 5.0-13.0 cm broad, convex, broadly so in age, often irregular with depressed and raised areas; margin incurved, then decurved, wavy; surface dry, glabrous to patchy appressed-fibrillose, pallid when unexposed, soon greyish to blackish-brown, sometimes with purplish tints, darker where handled; context white, firm, up to 3.0 cm thick at the disc, unchanging to slowly pale-grey; odor mild to fragrant; taste frequently bitter.
Pores fine, 3-4/mm, mostly angular, whitish, darkening when bruised; tube layer subdecurrent, 1.0-3.0 mm thick, not readily separable from the cap context.
Stipe 3.0-8.0 cm long, 2.0-4.0 cm thick, solid, central or eccentric, equal to ventricose, the base often pointed; surface colored like the cap but usually lighter, glabrous to squamulose, bruising dark greyish-brown; context white, firm, unchanging when cut except greyish at the base; partial veil absent.
Spores 5.0-6.0 x 4.0-5.0 µm, subglobose with a nodulose surface, inamyloid; spores hyaline to pale-tan in deposit.
Solitary, scattered, or in cespitose clusters in mixed hardwood-conifer woods; fruiting from late fall to mid-winter in coastal and montane forests; widely distributed; uncommon.
Edible but frequently bitter. The Japanese soak this mushroom in brine to remove the bitterness. Long boiling does not reduce the bitter flavor.
As the genus name suggests, this fleshy, grey, polypore mimics members of the bolete group, e.g. species of Suillus, Boletus, Leccinum, etc. As a polypore, however, it possesses a less putrescent context and tube layer that is not readily separable from the cap. Boletopsis grisea is most likely to be confused with other fleshy, terrestrial polypores, two of which are Albatrellus flettii and Jahnoporus hirtus. The former differs in having a bluish cap, and salmon-colored pores in age, while Jahnoporus hirtus has a grey-brown, occasionally purple-brown, tomentose cap. Microscopically, Boletopsis grisea is easily distinguished by its nodulose spores.
Bernicchia, A. (2005). Polyporaceae s.l. (Fungi Europaei). Edizioni Candusso: Alassio, Italy. 807 p.
Bessette, A.E., Roody, W.C. & Bessette, A.R. (2000). North American Boletes: A Color Guide to the Fleshy Pored Mushrooms. Syracuse University Press: Syracuse, NY. 400 p.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Peck, C.H. (1874). Report of the Botanist 1872. Ann. Rep. NY State Mus. 26: 35-91. (Protologue)
Watling, R. & Milne, J. (2008). The identity of European and North American Boletopsis spp. (Basidiomycota; Thelephorales, Boletopsidaceae). North American Fungi 3(7): 5-15. (PDF)