Cap 1.0-2.0 cm broad, convex to bell-shaped, expanding to plano-convex, often retaining a low umbo; margin translucent-striate when moist, finely appendiculate, initially decurved, nearly plane at maturity; surface glabrous, cuticle subviscid, separable from the cap, hygrophanous, fading from disc to margin, at first dingy dark reddish-brown to dull medium-brown, fading to dull orange-brown, eventually tan-buff; context thin, up to 2.0 mm thick at the disc, soft, cream-buff, darkening when cut, not bluing; odor not distinctive; taste slightly bitter.
Gills adnate to subdecurrent, sometimes extending as lines on the stipe apex, close, thin, broad, dull-tan when young, eventually dingy-brown, not purple-brown, edges lighter than the faces; lamellulae up to 4-seried.
Stipe 1.5-4.0 cm long, 1.0-3.0 mm thick, equal, cartilaginous, hollow at maturity; surface dry, the apex sometimes striate, elsewhere covered with buff to tawny-buff appressed or raised fibrils over a watery-brown background, white tomentose at the base, not bluing when bruised; partial veil evanescent, fibrillose, tan-buff, leaving fragments in an annular zone high on the stipe.
Spores 6.5-7.5 x 4.0-4.5 µm, lens-shaped, thick-walled, truncate with a germ pore at one end; spore print deep mahogany-brown.
Scattered, gregarious, or in rings in grassy areas, occasionally on dung and in other habitats ; fruiting from early to mid-winter.
Unknown; too small to have culinary value; not hallucinogenic according to Stamets.
Psilocybe subviscida is recognized by a strongly hygrophanous, subviscid, striate cap which fades from dull reddish-brown to tan-buff and a dark mahogany-brown spore print. Like many Psilocybe species, it has a viscid cuticle separable from the cap, but it lacks the characteristic bluing reaction of the genus. Although this Psilocybe has been reported from a variety of habitats, in the San Francisco Bay Area it appears to be most common in lawns and playing fields. Look-alikes include Panaeolus foenisecii, Agrocybe pediades and Tubaria furfuracea. Panaeolus foenisecii, a ubiquitous lawn mushroom, has a hygrophanous, brown cap, but the surface is not viscid. It is further distinguished by mottled gills and roughened spores. Agrocybe pediades is similar in size with a cream-buff sometimes sticky cap, but it lacks a striate margin and has a lighter brown spore print. Tubaria furfuracea, which grows commonly on wood chips as well as grass, has a hygrophanous, orange-brown, striate-margined cap, but the latter is not subviscid. Additionally, the gills and spores are dull orange-brown.