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Suillus intermedius

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

by Michael Kuo

This eastern Suillus species is fond of red pines, and can be identified by its yellowish, slimy cap; the blackening glandular dots on its stem; the orangish flesh inside the stem; and the distinctive ring, which is at first bracelet-like and gelatinous but later collapses to create a dry, grayish zone on the upper stem. Many authors emphasize that the taste of the slime on the cap's surface is acidic or sour; you are welcome to experiment, but I doubt you will need to take this one for the team in order to correctly identify Suillus intermedius--and the taste, in my experience, is variable anyway.


Ecology: Mycorrhizal with pines--perhaps exclusively with red pine; growing alone, scattered, or gregariously; summer and fall; northeastern and northern North America.

Cap: 3-17 cm; convex becoming more or less flat; smooth; slimy; yellowish, darkening somewhat with age; often with yellowish partial veil remnants on the margin.

Pore Surface: Pale yellow when young, darker yellow at maturity; not bruising, or bruising slowly brownish; 2-3 angular pores per mm; tubes to 6 mm deep.

Stem: 4-10 cm long; up to 12 mm thick; more or less equal; fairly tough; yellowish below brownish glandular dots that blacken with maturity; usually blackening on handling; when young with a thin, bracelet-like, gelatinous ring that dries out and flattens against the stem surface with maturity.

Flesh: Whitish to yellowish in the cap; pale salmon orange in the stem; not staining on exposure.

Odor and Taste: Odor not distinctive; taste of the slime on the cap acidic or mild.

Chemical Reactions: Ammonia negative to grayish on cap surface; purplish red to bright pink, grayish, or brownish on flesh. KOH bluish gray to brownish on cap surface; bluish to gray on flesh. Iron salts negative on cap surface; negative to greenish on flesh.

Spore Print: Cinnamon brown.

Microscopic Features: Spores 8-11 x 3.5-5 µ; smooth; subfusoid.

Suillus acidus var. intermedius is a previous name. Suillus acidus Peck (1906) has a whiter cap. It may well be the same mushroom as Suillus intermedius--in which case Suillus acidus is the older name and should take precedence.

REFERENCES: (Smith & Thiers, 1964) Smith & Thiers, 1971. (Smith & Thiers, 1964; Snell & Dick, 1970; Smith & Thiers, 1971; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; Phillips, 1991/2005; Both, 1993; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006.) Herb. Kuo 09019510, 09030203, 09150702.

Further Online Information:

Suillus intermedius in Smith & Thiers, 1971
Suillus intermedius at Roger's Mushrooms


Suillus intermedius

Suillus intermedius

Suillus intermedius

Suillus intermedius

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Kuo, M. (2007, December). Suillus intermedius. Retrieved from the MushroomExpert.Com Web site: