Cap 2.0-6.0 cm broad, convex to convex-umbonate, nearly plane with a low umbo at maturity; margin incurved, then decurved, level to upturned in age, sometimes wavy; surface viscid, glabrous, hygrophanous, the disc yellowish-brown to tawny-brown, with similar colored innate fibrils extending outward to a cream-buff to dingy pale-yellow margin; context cream-yellow, soft, unchanging, up to 5 mm thick near the stipe; odor and taste not distinctive.
Gills adnexed, adnate, notched, to subdecurrent, subdistant; at first cream-yellow, then pale yellowish-buff, discoloring brown where bruised, tan-brown in age; gills moderately broad, up to 5 mm in width, edges mostly even; lamellulae in four to five series.
Stipe 2.0-6.0 cm long, 3-8 mm thick, equal to narrowed slightly towards the base, straight to flexuous, hollow in age; surface dry, cream-yellow at apex, pallid to buff-colored below, obscurely appressed-fibrillose, lower portion discoloring brown with handling; partial veil fibrillose, cream-colored, evanescent, leaving scattered fibrils on the stipe, often dingy reddish-brown from spore deposit.
Spores 6.0-9.5 x 4.0-5.5 µm, elliptical to oblong-elliptical in face-view, similar in profile, smooth, thin-walled, germ pore present but inconspicuous, hilar appendage inconspicuous; spore dingy reddish-brown in deposit.
Scattered, gregarious to clustered on conifer wood in coastal and montane forests; also present on sawdust piles and wood chips; fruiting throughout the mushroom season after periods of rain; locally common.
No single feature defines Pholiota spumosa. Nonetheless, it has a "look" that with experience makes it relatively easy to identify. In the San Francisco Bay area, Pholiota spumosa has a viscid, hygrophanous, glabrous cap that is tawny to yellow-brown at the disc, cream to pale-yellow at the margin, but lacks the olivaceous tones cited by Smith and Hesler in a monograph of the genus. An evanescent fibrillose partial veil, mild odor and taste, plus a dingy reddish-brown spore print are also helpful identifying characters. Pholiota spumosa is part of a group of wood-rotting fungi that have taken advantage of the practice of mulching roadsides and parks with wood chips. The result is that some of these species are more common here than in the wild. Several bear a resemblance to Pholiota spumosa, thus should be compared closely. These include Hypholoma fasiculare (Sulphur Tuft), Agrocybe praecox, Agrocybe putaminum, and Stropharia riparia. The Sulphur Tuft is typically more yellowish in color and has a non-viscid cap, yellow-green gills, bitter taste, and purple-brown spores; Stropharia riparia differs in possessing an evenly colored cream-yellow, non-viscid cap and purple-brown spores; Agrocybe praecox resembles Stropharia riparia with a cream to buff-colored, non-viscid cap, but in addition has a membranous annulus and dull brown spores; a more robust cousin Agrocybe putaminum too has a nonviscid buff-colored cap, but lacks an annulus; its spores are dull brown, not dingy reddish-brown in deposit.