|Major Groups > Boletes > Boletus > Boletus subtomentosus|
by Michael Kuo
This common bolete can be a nightmare to identify if you don't have a drop of common household ammonia handy. Maybe it's just me, but every time I find Boletus subtomentosus, I promptly forget most of what I know about boletes and spend hours trying to figure out what I've found. It's just such an average bolete; nothing really seems to stand out as a distinctive identification feature.
Except the ammonia thing: a drop on the cap produces an instant mahogany red reaction. This will separate Boletus subtomentosus from some of the other species of "boletish" (the ones that are velvety-ish and brownish-capped, with yellowish pore surfaces that bruise-ish faintly bluish or greenish), including Boletus spadiceus and Boletus illudens, both of which flash green with ammonia before resolving to reddish brown.
Ecology: Mycorrhizal with hardwoods or conifers; growing alone or scattered; summer and fall; widely distributed in North America.
Cap: 5-18 cm; convex, becoming broadly convex or almost flat; dry; finely velvety; often becoming cracked in age, with yellowish flesh showing in the cracks; olive to olive brown, or yellowish brown, sometimes faintly reddish in age; margin incurved when young, with a projecting sterile portion.
Pore Surface: Yellowish; bruising slowly greenish, then brown; 1-2 pores per mm; tubes 1-2.5 cm deep.
Stem: 4-10 cm long; 1-2 cm thick; more or less equal, or tapering near the base; solid; yellowish, with reddish brown stains; basal mycelium sulphur yellow; not reticulate, but often with ridges approaching an obscure reticulum, especially near the apex; bruising slowly brownish to reddish brown on handling.
Flesh: White or pale yellow; not staining on exposure, or staining faintly blue.
Odor and Taste: Not distinctive.
Chemical Reactions: Cap instantly mahogany red with ammonia.
Spore Print: Olive brown.
Microscopic Features: Spores 10-15 x 3-5 µ; smooth; subfusiform.
REFERENCES: Fries, 1821. (Coker & Beers, 1943; Snell & Dick, 1970; Smith & Thiers, 1971; Thiers, 1975; Smith, Smith & Weber, 1981; Phillips, 1991/2005; Lincoff, 1992; Both, 1993; Bessette, Roody & Bessette, 2000; McNeil, 2006.) Herb. Kuo 07140310.
Xerocomus subtomentosus is a synonym.
Smith & Thiers (1971) record a variety from Michigan, Boletus subtomentosus var. perplexus; its pore surface bruises promptly greenish blue (rather than slowly green, then brown), and its basal mycelium is pallid (rather than sulphur yellow). It also differs on microscopic features.
Further Online Information:
Cite this page as:
Kuo, M. (2003, March). Boletus subtomentosus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_subtomentosus.html