Boletus inedulis

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

by Michael Kuo

This eastern mushroom is a study in interesting colors: the pale cap, yellow pore surface, pinkish red stem and white flesh form a rather attractive combination--accentuated by the indigo blue bruising of the pore surface and the sky blue staining of the exposed flesh. The taste of this mushroom is bitter, rendering it inedible. Several species, also bitter tasting, are similar in appearance; see the comments below for help separating Boletus inedulis from its look-alikes.

Description:

Ecology: Mycorrhizal with hardwoods (especially oaks), or with Eastern Hemlock; growing alone or gregariously; summer and fall; widely distributed in eastern North America.

Cap: 4-12 cm; convex, becoming broadly convex or nearly flat in age; dry; smooth, or finely velvety when young, often cracked in age, with white flesh showing in the cracks; margin inrolled, with a narrow overhanging sterile portion; whitish to pale tan.

Pore Surface: Yellow, becoming olive yellow; bruising blue; pores circular, 1-3 per mm; tubes to 16 mm deep.

Stem: 5-12 cm long; 1-2 cm thick; tapered upward or nearly equal; yellowish at apex, reddish below; bruising blackish brown in the lower portion; sometimes faintly reticulate but also often smooth and lacking reticulation.

Flesh: White to yellowish; staining blue on exposure.

Odor and Taste: Odor not distinctive; taste bitter.

Chemical Reactions: KOH on cap surface pale orange; on flesh orangish. Ammonia negative on cap surface and flesh. Iron salts grayish on cap surface; negative on flesh..

Spore Print: Olive brown.

Microscopic Features: Spores 9-13 x 3.3-4.5 µ; smooth.

REFERENCES: Murrill, 1938. (Singer, 1947; Snell & Dick, 1970; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Phillips, 1991/2005; Both, 1993; Bessette, Roody & Bessette, 2000; McNeil, 2006; Ortiz-Santana et al., 2007.) Herb. Kuo 08309703, 08300208, 06300708.

Boletus calopus is larger, has a darker cap, and substantially larger spores (13-19 x 5-6 µ). Boletus roseipes grows only with hemlock and has an olive brown cap when young. Boletus rubripes is found west of the Rocky Mountains and has spores 12-18 x 4-5 µ. Boletus glabellus lacks the bitter taste and has deep yellow flesh in the base of the stem.

Further Online Information:

Boletus inedulis in Smith & Thiers, 1971
Boletus inedulis at Roger's Mushrooms

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Cite this page as:

Kuo, M. (2002, September). Boletus inedulis. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_inedulis.html