Suillus americanus
Lloydia 7(1): 39. 1944.
Common Name: none
Synonym: Suillus sibiricus (Singer) Singer
5-10 cm broad when mature, broadly conic to convex when young, becoming broadly convex to plane to umbonate at maturity; surface viscid, when very young appearing glabrous to streaked with gluten, sometimes with plaques or scales toward the margin, with age glabrous on the disc or with scattered inconspicuous plaques to conspicuous plaques on the disc; when young background color yellow ("mustard yellow" to "Isabella color") with the gluten and plaques colored reddish ("russet"), with age background changing to dark yellow ("chamois" to "honey yellow") and the plaques brown to reddish brown ("Mikado brown" to "pecan brown"), tending to stain vinaceous when bruised; margin strongly incurved to inrolled, when young with a highly conspicuous roll of cottony veil tissue colored whitish to pale yellow, but with age whitish to grayish white, becoming glabrous with age. Context 1-2 cm thick, yellow ("Naples yellow"), but typically staining vinaceous when exposed. Taste of gluten acid; otherwise taste and odor mild. (From Thiers 1975)
7-10 mm long, decurrent, when very young yellow ("mustard yellow"), darkening to dull yellow ("antimony yellow" to "yellow ocher") with age, staining vinaceous to dirty pink when bruised; pores up to 2 mm broad, elongated to rectangular, typically radially arranged but not always so, compound, concolorous with tubes. (From Thiers 1975)
5-11 cm long, 0.5-1 cm thick at the apex, equal, solid, sometimes appearing hollow with age; surface moist to subviscid, staining fingers black when handled, glandular, glands pallid and inconspicuous when young, becoming brown to yellow brown with age; background color yellow ("Naples yellow" to "mustard yellow"), staining brown to vinaceous when bruised; annulus sometimes present, often evanescent. (From Thiers 1975)
Spore print brown. Spores 8-12 X 3.8-4.5 µm, subellipsoid to subcylindric, ventricose in side view, smooth, thin-walled. (From Thiers 1975)
Scattered to gregarious in soil under western white pine. This species has not yet been recorded from California so far as is known. It is common, however, in several western states, and is included here since western white pine is relatively widely distributed within the northern half of the state. (From Thiers 1975)
Edible; some susceptible individuals may suffer a contact dermatitis after touching the fruit bodies.
It is readily apparent that S. americanus is very close to S. sibiricus, and considerable difficulty is encountered in separating these two species. Perhaps the most obvious and constant difference is seen in the tendency of the context of the stipe base to stain vinaceous in S. sibiricus. As has already been indicated, it is now believed that S. americanus does not occur west of the Rocky Mountains and that many reports of its presence in the west have been based upon basidiocarps of S. sibiricus. (From Thiers 1975)
Although there is some minor macro-morphological differences between western Suillus sibiricus and eastern Suillus americanus, recent molecular work indicated they are the same species, with S. americanus the correct name (see Nguyen et al.).
Arora, D. (1986). Mushrooms Demystified. Ten Speed Press: Berkeley, CA. 959 p.
Bessette, A.E., Roody, W.C. & Bessette, A.R. (2000). North American Boletes: A Color Guide to the Fleshy Pored Mushrooms. Syracuse University Press: Syracuse, NY. 400 p.
Bruhn, J.N. & Soderberg, M.D. (1991). Allergic contact dermatitis caused by mushrooms. Mycopathologia 115(3): 191-195.
Klofac, W. (2013). A world-wide key to the genus Suillus. Österr. Z. Pilzk 22: 211-278. (PDF)
Nguyen, N.H., Vellinga, E.C., Bruns, T.D. & Kennedy, P.G. (2016). Phylogenetic assessment of global Suillus ITS sequences supports morphologically defined species and reveals synonymous and undescribed taxa. Mycologia 108(6): 1216-1228.
Peck, C.H. (1887). Contributions to the Botany of the State of New York. Bulletin of the New York State Museum 1(2): 1-66. (Protologue) (PDF)
Smith, A.H. (1949). Mushrooms in their Natural Habitats. Sawyer's Inc: Portland, OR. 626 p. (PDF)
Smith, A.H. & Thiers, H.D. (1971). The Boletes of Michigan. University of Michigan Press: Ann Arbor, MI. 426 p. (PDF)
Smith, A.H. & Thiers, H.D. (1964). A Contribution Toward A Monograph of North American Species of Suillus. Privately Published: Ann Arbor, MI. 116 p. (PDF)
Thiers, H.D. (1975). The status of the genus Suillus in the United States. Beih. Nova Hedw. 51: 247-278.
Thiers, H.D. (1975). California Mushrooms—A Field Guide to the Boletes. Hafner Press: New York, NY. 261 p. (WWW)
Thiers, H.D. (1979). The genus Suillus in the Western United States. Mycotaxon 9(1): 285-296. (PDF)
— Same species, Eastern US (Tennessee)
