Members of the genus Suillus are aptly termed "Slippery Jacks," due to their slimy, viscid caps, and S. caerulescens is no exception. The caps are 5-18 cm broad, viscid when moist, and are often a dull, streaked yellow- to orange-brown color in the center, blending to a lighter yellowish color near the margin. As a member of the family Boletaceae (Agaricales) they possess pores on the undersides of the caps instead of gills. The pores are typically radially arranged, bright yellow when young (fading to dull yellow-brown with age), and often discolor brown when bruised. Basidiospores are 7-11 x 3-5 µm, elliptical to spindle-shaped, and smooth. Spore prints are brown to dull cinnamon in color. Stalks are typically 2.5-10 cm long, 1.5-3 cm thick with a mottled, stained appearance, and are sometimes spotted but not glandular-dotted like other Suillus species. Stalks are firm, dry, and yellow above the annulus, and fibrillose and dingier below. Flesh at the base of the stalk typically turns blue or green when cut. The partial veil is whitish when young, dingier in age (similar to cap color), usually forming an annulus on the stalk.
Ecology
Suillus caerulescens is commonly referred to as the "Douglas Fir Suillus" and is a common bolete in Douglas Fir (Pseudotsuga menziesii) forests, especially in the Pacific Northwest. In fact, the species is found only in the Pacific Northwest and California, and is mycorrhizal with Douglas Fir. Suillus caerulescens can often be found growing near members of the Gomphidiaceae, such as Gomphidius or Chroogomphus, and it is possible that the fungal mycelia of S. caerulescens associate with these fungi as well as with their Douglas Fir hosts. A morphologically similar species, S. ponderosus, is also common throughout the range that S. caerulescens occupies, and is distinguished by its yellow or orange partial veil. The largest fruiting of S. caerulescens sporocarps occurs in late fall, but the species can be found fruiting from fall through early spring.
Sources
Arora, D. 1986. Mushrooms demystified, a comprehensive guide to the fleshy
fungi. 2nd ed. Ten Speed Press, Berkeley, California, USA.
