Major Groups > Boletes > Red-Pored Boletes > Boletus frostii


Boletus frostii

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

by Michael Kuo

The sticky red cap of this fairly unmistakable bolete is red--like, the primary color red--rather than the "red" of so many bolete species that are actually brownish red or rusty red (and so on). Other distinguishing features for Boletus frostii include its red pore surface; its deeply and coarsely reticulate stem; and the fact that its pore surface and flesh bruise promptly blue. Boletus frostii is a mycorrhizal associate with hardwoods--especially oaks--in eastern North America, pockets of the Southwest, Mexico, and Central America.


Ecology: Mycorrhizal with oaks and other hardwoods; growing alone, scattered, or gregariously; summer and fall; widely distributed in eastern North America, Texas, pockets of the Southwest, Mexico, and Central America.

Cap: 3.5-8 cm, convex, becoming broadly convex; sticky or thinly slimy when fresh; bald, or very finely and shallowly pock-marked; bright red, developing yellowish areas with age; the margin with a slight (1 mm) overhanging sterile portion.

Pore Surface: Dark to pale red when young, becoming dirty brownish red; bruising promptly dark blue; often exuding yellowish droplets when young; 2-3 pores per mm; tubes yellowish to olive, to 15 mm deep.

Stem: 4-8 cm long; up to 2 cm thick; more or less equal; coarsely and prominently reticulate over the entire length; red, or occasionally with yellow areas; often bruising blue.

Flesh: Whitish to yellow; bluing when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia negative or blackish on cap; grayish or orangish on flesh. KOH black or grayish, then quickly orangish on cap surface; orange to grayish orange on flesh. Iron salts negative to gray on cap surface; negative on flesh.

Spore Print: Olive brown.

Microscopic Features: Spores 11-17 x 4-5 µ; smooth; fusiform; yellow in KOH. Pileipellis a tangled layer of gelatinized, hyaline hyphae 3-6 µ wide over a layer of yellow elements 5-13 µ wide.

REFERENCES: Russell (in Frost), 1874. (Saccardo, 1891; Coker & Beers, 1943; Singer, 1947; Snell & Dick, 1970; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Weber & Smith, 1985; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Metzler & Metzler, 1992; Both, 1993; Bessette, Roody & Bessette, 2000; Roody, 2003; Miller & Miller, 2006; Binion et al., 2008.) Herb. Kuo 08160601, 08111208.

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Boletus frostii

Boletus frostii

Boletus frostii

Boletus frostii

Boletus frostii

Boletus frostii
Chemical reactions
L to R: ammonia, KOH, iron salts

Boletus frostii

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Kuo, M. (2013, December). Boletus frostii. Retrieved from the MushroomExpert.Com Web site: