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Boletus luridus

[ Basidiomycota > Boletales > Boletaceae > Boletus . . . ]

by Michael Kuo

This impressive mushroom, associated primarily with oaks in eastern North America, is a blue-staining bolete with a red to orange pore surface, a brown to brownish cap, and a stem decorated with prominent reddish reticulation. Several North American species will meet this broad description, and most of them lack official names. The true Boletus luridus is a European species first named in the 18th century; it is not likely that our North American versions actually represent the same phylogenetic species, although they are morphologically very similar. Here I have described and illustrated the version of "Boletus luridus" I collect in the Midwest.


Ecology: Mycorrhizal with oaks and other hardwoods; growing alone, scattered, or gregariously; summer and fall; widely distributed east of the Rocky Mountains.

Cap: 4-12 cm, convex, becoming broadly convex in age; dry; finely velvety or nearly bald; brownish orange at first, becoming rusty brown to medium or dark brown; bruising dark blue to nearly black.

Pore Surface: Dull orange when young; orangish red to reddish orange at maturity; bruising promptly blue; 2-4 pores per mm; tubes to 15 mm deep.

Stem: 4-9 cm long; up to 3 cm thick; tapering to the apex; slightly club-shaped when young, becoming more equal; often with a tapered, rooting portion; prominently reticulate with vertically elongated, orange to red reticulation; often with a red to wine red, velvety base; yellowish to orangish above and reddish below; bruising and discoloring blue.

Flesh: Whitish to yellow in the cap; yellow to red in the stem; bluing when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia negative to orangish or yellowish on cap; yellow to orangish on flesh. KOH dark red on cap; dull orange on flesh. Iron salts olive gray on cap; negative to dull olive yellow on flesh.

Spore Print: Olive brown.

Microscopic Features: Spores 11-14 x 4.5-6 µ; broadly fusiform to nearly ellipsoid; smooth; brownish in KOH. Hymenial cystidia fusiform; hyaline to brownish in KOH; to about 50 x 15 µ. Pileipellis a tightly packed layer of repent and erect, brown-encrusted elements 2.5-5 µ wide; terminal elements subfusiform, or cylindric with rounded apices.

REFERENCES: Schaeffer, 1774. (Fries, 1821; Saccardo, 1888; Singer, 1945; Snell & Dick, 1970; Smith & Thiers, 1971; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; Breitenbach & Kränzlin, 1991; Both, 1993; Bessette, Roody & Bessette, 2000; Binion et al., 2008.) Herb. Kuo 07140402, 08240507, 07010701, 07141402.

This site contains no information about the edibility or toxicity of mushrooms.


Boletus luridus

Boletus luridus

Boletus luridus

Boletus luridus

Boletus luridus
Ammonia, KOH, iron salts

Boletus luridus

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Kuo, M. (2015, January). Boletus luridus. Retrieved from the MushroomExpert.Com Web site: