Distinguishing Characters: Boletoid stature; pileus pallid yellowish background spotted with reddish brown patches composed of appressed squamules, often slightly umbonate, glutinous, margin covered with evanescent, thin, floccose veil remnants; pore surface yellowish, bruising brownish orange, depressed to decurrent; stipe often slightly over 1 cm in diam., glandulose, reddish brown glandulae covering a dull yellowish background, vinaceous stains developing toward base; veil evanescent, thin, floccose whitish to dull yellowish; spores ellipsoid to subcylindric, smooth, 8.0-11.0 x 3.8-4.2 µm; growing in association with conifers.

Compare: Suillus americanus - pileus bright yellow background spotted with reddish brown patches or streaks of reddish fibrils, often remaining bright yellow with age; stipe typically less than 1 cm in diam.; spores 8.0-11.0 (12) x 3.0-4.0 µm; growing in association with Eastern White Pine - Pinus strobus L. Suillus umbonatus - pileus dull yellowish brown to pallid olive brown or olive-gray; stipe typically less than 1 cm in diam., often gelatinous below the veil; veil gelatinous and somewhat membranous, drying to dull reddish brown appressed zone; spores 7.0-9.0 (10) x 4.0-4.5 µm.

Bassette, A.E., W.C. Roody and A.R. Bessette. 2000. North American Boletes: A Color Guide to the Fleshy Pored Mushrooms. Syracuse University Press, Syracuse.

Kuo, M. 2004. Suillus americanus. Retrieved 24 Aug 2006 from http://www.mushroomexpert.com/suillus_americanus.html.

Thiers, H.D. 1975. California Mushrooms: A Field Guide to the Boletes. Hafner Press, New York.

Thiers, H.D. 1976. Boletes of the Southwestern United States. Mycotaxon 3: 261-273.

Smith, A.H. and H.D. Thiers. 1964. A Contribution Toward a Monograph of North American Species of Suillus. Privately published, Ann Arbor.

Wood, M. 2006. Suillus umbonatus. Retrieved 24 Aug 2006 from http://www.mykoweb.com/CAF/species/suillus_umbonatus.html.