|Major Groups > Boletes > Boletus > Boletus spadiceus|
by Michael Kuo
Distinguishing features for Boletus spadiceus include its preference for conifers; its finely velvety, medium-sized, brown cap; the coarse pattern of ridges at the stem apex, suggestive of reticulation that never got fully developed; and the green flash that results from the application of ammonia to the cap surface. Some collections demonstrate faint to moderate bluing of the bruised pore surface and/or sliced flesh--but the bluing is often absent. Boletus spadiceus is widely distributed in North America, but apparently not common. Boletus subtomentosus is very similar, but its cap surface turns dark red with ammonia.
Ecology: Mycorrhizal with conifers; growing alone, scattered, or gregariously; often reported from disturbed-ground areas (ditches, road banks, and so on); summer and fall; fairly widely distributed in North America.
Cap: 5-15 cm; convex, becoming broadly convex or almost flat; dry; finely velvety; sometimes becoming cracked in age; brown, olive brown to olive buff, or yellowish brown--but not uncommonly reddish brown, especially when wet.
Pore Surface: Yellow, becoming olive yellow; sometimes bruising greenish to bluish; pores angular, especially near the stem, 1-2 mm wide; tubes to 1.5 cm deep.
Stem: 5-12 cm long; 1-3 cm thick; more or less equal; solid; usually featuring coarse brownish to reddish brown lines near the apex in a nearly reticulate pattern; granular (almost appearing to have glandular dots) to smooth below; yellowish to yellow.
Flesh: White or pale yellow; not staining on exposure, or staining faintly bluish to greenish in places.
Odor and Taste: Pleasant; not distinctive.
Chemical Reactions: Ammonia flashing green to blue-green on cap surface, then resolving to reddish brown; negative on flesh. KOH blackish red on cap surface ("olive becoming black" according to Grund & Harrison, 1976; "dark brown" according to Thiers, 1975); orangish to brownish on flesh. Iron salts negative on cap surface; negative to olive on flesh.
Spore Print: Olive brown.
Microscopic Features: Spores 9-14 x 4-5.5 µ; smooth; subfusiform; yellow in KOH. Hymenial cystidia fusoid-ventricose to subfusoid or mucronate; hyaline in KOH; to about
REFERENCES: Fries, 1838. (Saccardo, 1888; Snell & Dick, 1970; Smith & Thiers, 1971; Thiers, 1975; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; Phillips, 1991/2005; Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 08100701.
Xerocomus spadiceus is a synonym.
Boletus spadiceus var. gracilis is similar but smaller (stem under 1 cm thick); it is found primarily under hardwoods in eastern North America.
Further Online Information:
Cite this page as:
Kuo, M. (2007, December). Boletus spadiceus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_spadiceus.html