Boletus pallidus

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by Michael Kuo

Does the pore surface bruise blue? Maybe, maybe not. Does the flesh turn bluish on exposure? Maybe, maybe not--or maybe it feels like turning pinkish. Don't mushrooms read the field guides and monographs to find out what they're supposed to do?!

Don't rely heavily on color changes from bruising or exposure to air for your identification decisions with this mushroom (within reason; if your mushroom instantly changes to blackish blue when you slice it open, it's definitely not Boletus pallidus). Look for the pale cap, smooth white stem, yellowish to olive pore surface, and the olive to olive brown (not yellow brown) spore print.

Boletus pallidus is probably not a safe edible for beginners. It isn't the easiest of boletes to identify; there are several close look-alikes, and there is the problem with staining and bruising mentioned above. Experienced collectors who are sure of their identification may want to try it, despite the fact that it (sometimes) bruises blue. I have tried it, dried and reconstituted (in filling for ravioli alfredo), and found it good.

Description:

Ecology: Mycorrhizal with hardwoods, especially oaks; growing alone, gregariously, or in small clumps; summer and fall; widely distributed in eastern North America.

Cap: 4-15 cm; convex, becoming broadly convex or nearly flat in age; dry; smooth or very finely velvety; sometimes becoming finely cracked in age; the margin often with a tiny overhanging sterile portion; whitish to buff or pale tan, sometimes developing rose shades.

Pore Surface: Whitish to yellowish when young, becoming yellow to greenish yellow; bruising bluish, then brownish--or not bruising; pores circular, becoming angular, 1-2 per mm; tubes to 20 mm deep.

Stem: 5-12 cm long; 1-2.5 cm thick; more or less equal; white; sometimes yellowish at apex, sometimes with pale reddish colors below in age (but not as strikingly or consistently red as the stem of Boletus inedulis); sometimes developing brownish streaks; not reticulate; basal mycelium white.

Flesh: Whitish to pale yellow; typically staining slowly and erratically pale blue on exposure, especially above the tubes--but often not staining, or staining pinkish.

Odor and Taste: Not distinctive.

Chemical Reactions: Cap surface rusty orange with KOH, pale orange with ammonia or iron salts; flesh rusty orange with KOH, blue-green with ammonia, negative with iron salts; pore surface rusty orange with KOH, blue-green with ammonia, rusty orange with iron salts. I have not found the reactions to ammonia and iron salts to be completely consistent with these "official" color changes.

Spore Print: Olive to olive brown.

Microscopic Features: Spores 9-15 x 3-5 µ; smooth.

REFERENCES: Frost, 1874. (Saccardo, 1891; Coker & Beers, 1943; Singer, 1947; Snell & Dick, 1970; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Phillips, 1991/2005; Both, 1993; Barron, 1999; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Kuo, 2007; Ortiz-Santana et al., 2007.) Herb. Kuo 07319701, 09050202, 08160604, 09150717.

The similar Boletus alutaceus is somewhat smaller, never bruises or stains blue, has a lighter spore print, fatter spores, and often has a yellowish stem base.

Further Online Information:

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

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Cite this page as:

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