[ Basidiomycetes > Boletales > Boletaceae > Boletus . . . ]
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.
Kuo, M. (2003, March). Boletus subtomentosus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_subtomentosus.html
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