Major Groups > Boletes > Boletus > Boletus pseudosulphureus


Boletus pseudosulphureus

[ Basidiomycetes > Boletales > Boletaceae > Boletus . . . ]

by Michael Kuo

This unkempt bolete reminds me of Boletus pulverulentus in its sloppiness. Button-stage specimens are uniformly bright yellow, but things soon deteriorate, and the mushroom's personal grooming skills go to hell in a handbasket; the cap develops orangish to reddish discolorations, the pore surface turns a sickly brownish olive, and the stem bruises blue, then dirty brown.

Boletus pseudosulphureus makes an early appearance in bolete season, often appearing even in May. It is primarily mycorrhizal with hardwoods, but is occasionally reported under conifers. In central Illinois a dwarf form (illustrated) is fairly common in early summer, identical in all respects to its larger namesakes, except for its diminutive size.


Ecology: Mycorrhizal with hardwoods and sometimes with conifers; growing alone, scattered, or gregariously; late spring, early summer, or summer; widely distributed in eastern North America.

Cap: 4-9 cm; cushion-shaped, becoming convex, broadly convex, or almost flat; dry; finely velvety when young, becoming fairly smooth, or cracked with age; bright yellow, developing orangish to reddish discolorations; bruising promptly blue to black; the margin with an overhanging sterile portion up to 1 mm wide.

Pore Surface: Bright yellow, becoming olive; bruising promptly blue or greenish; 2-3 pores per mm at maturity; tubes to about 1 cm deep.

Stem: 8-12 cm long; 1-1.5 cm thick; more or less equal; dry; solid; yellow above, reddish below--or occasionally yellow overall; smooth; not reticulate; bruising greenish to bluish, then grayish brown.

Flesh: Yellow; often red in the stem base; staining quickly blue on exposure.

Odor and Taste: Taste not distinctive or acidic; odor not distinctive.

Chemical Reactions: Ammonia negative on cap surface. KOH orange to red on cap surface and flesh. Iron salts gray to grayish olive on cap surface.

Spore Print: Olive brown.

Microscopic Features: Spores 10-14 x 4.5-6 µ; smooth; broadly fusiform.

REFERENCES: Kallenbach, 1923. (Snell & Dick, 1970; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Weber & Smith, 1985; Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 05210402, 05280704.

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


Boletus pseudosulphureus

Boletus pseudosulphureus

Boletus pseudosulphureus

© MushroomExpert.Com

Cite this page as:

Kuo, M. (2005, March). Boletus pseudosulphureus. Retrieved from the MushroomExpert.Com Web site: