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Suillus caerulescens

[ Basidiomycetes > Boletales > Suillaceae > Suillus . . . ]

by Michael Kuo

This messy Suillus is a mycorrhizal associate of Douglas-fir in western North America. It seems as though it ought to be easily distinguished; the flesh in its stem turns blue on exposure (rare in species of Suillus), and its pore surface slowly bruises a distinctive reddish clay color.

Suillus imitatus has a cap that is "glabrous or practically so, if fibrillose-streaked the fibrils beneath the gluten" (Smith & Thiers, 1964). It also has a slimy, yellowish partial veil, and slightly shorter spores (7-9 µ long). Suillus imitatus var. viridescens develops greenish to olive or bluish shades on the cap surface.


Ecology: Mycorrhizal with Douglas-fir and other conifers; growing alone or gregariously; fall and winter; western North America.

Cap: 6-14 cm; convex becoming broadly convex or flat; moist or fairly slimy; smooth or with patches of appressed fibers or scales; yellowish brown to tawny or cinnamon brown; the margin sometimes hung with partial veil remnants.

Pore Surface: Yellowish; bruising slowly reddish brown; pores angular and radially arranged (but not boletinoid), about 1-2 mm across; tubes to about 1 cm deep.

Stem: 3-8 cm long; 2-3 cm thick; more or less equal, or tapered in either direction; solid; often finely reticulate near the apex; smooth or with appressed hairs; lacking glandular dots; yellowish above, dingy to brownish below; bruising brown; with a whitish, dry ring that soon collapses or disappears entirely.

Flesh: Pale yellow; staining blue in the stem base when exposed, elsewhere not staining or staining pinkish to brownish.

Odor and Taste: Mild or slightly acidic.

Chemical Reactions: Ammonia grayish on cap; pale grayish lilac on flesh. KOH olive gray becoming dark gray on cap; dark gray on flesh. Iron salts olive on cap; olive to bluish on flesh.

Spore Print: Cinnamon brown.

Microscopic Features: Spores 8-11 x 3-5 µ; smooth; subfusoid.

REFERENCES: Smith & Thiers, 1964. (Smith & Thiers, 1964; Thiers, 1975; Smith, Smith & Weber, 1981; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 01130517.

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Suillus caerulescens

Suillus caerulescens

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Kuo, M. (2005, March). Suillus caerulescens. Retrieved from the MushroomExpert.Com Web site: