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


Boletus rubroflammeus

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

by Michael Kuo

Boletus rubroflammeus is a red-pored, red-capped, blue-staining bolete from eastern North America's hardwood forests. Its stem is beautifully reticulate with a red, net-like pattern, and its cap surface turns fleetingly bluish purple with ammonia (a fact not previously reported, to my knowledge). When young the cap is matted with a grayish material that soon all-but disappears, but can be found along the margin of the mature cap. Look-alike eastern boletes include Boletus flammans (appearing only under conifers), Butyriboletus floridanus (limited to the southeast, mature pore surface more orange, cap not initially matted with grayish material), and Boletus rhodosanguineus (stem more yellow, especially toward base; cap becoming mottled with browns; odor very strong and sickly sweet).


Ecology: Mycorrhizal with hardwoods, but precise host associations undocumented in the literature (the illustrated and described collection was made in a grassy area under oaks and hickories); growing alone, scattered, or gregariously; summer; possibly widely distributed east of the Rocky Mountains. The illustrated and described collection is from Illinois.

Cap: 6-12 cm; convex, becoming broadly convex; dry; finely velvety when very young, but soon bald; purplish red to pinkish red, hardly fading; when young often matted with a grayish material that is later visible along the margin.

Pore Surface: Dark red at first, but fading somewhat; bruising promptly blue; with 2-3 circular to angular pores per mm; tubes to 2 cm deep.

Stem: 6-8 cm long; 1-3 cm thick; more or less equal; orange-yellow at the apex and the base, especially when young; colored like the cap overall; dry; reticulate with a fine red reticulum over the upper half; bald underneath the reticulum; basal mycelium yellowish.

Flesh: Pale yellow in cap; sometimes with reddish streaks in stem; staining promptly blue when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia quickly bluish purple, then negative on cap surface; negative to grayish on flesh. KOH dull orange or yellow on cap surface; dull orange on flesh. Iron salts gray on cap surface; negative on flesh.

Spore Print: Color not documented.

Microscopic Features: Spores 10.5-13 x 4-5 µ; subfusiform; smooth; yellow in KOH. Hymenial cystidia lageniform; to about 40 x 15 µ. Pileipellis a cutis of elements 4-6 µ wide, occasionally cystidioid,hyaline to orangish brown in KOH.

REFERENCES: Smith & Thiers, 1971. (Smith, Smith & Weber, 1981; Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 08239703, 08291404.

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Boletus rubroflammeus

Boletus rubroflammeus

Boletus rubroflammeus

Boletus rubroflammeus

Boletus rubroflammeus
Ammonia, KOH, iron salts

Boletus rubroflammeus

Boletus rubroflammeus

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Kuo, M. (2014, December). Boletus rubroflammeus. Retrieved from the MushroomExpert.Com Web site: