Trans. Amer. Philos. Soc., n. s. 7: 341. 1840.
Plants greenish to grayish, arachnoid to ± sericeous. Stems (1–)2–10, ascending to ± prostrate; proximal internode lengths mostly 1–2(–3) times leaf lengths. Capitular leaves ± spreading, mostly not appressed to heads, spatulate to obovate, widest in distal 1/3, longest 6–15 mm, lengths mostly 2–5 times widths, 1.5–2.5(–3) times head heights. Heads ± spheric, largest 3–5.5 mm. Receptacles unlobed. Pistillate paleae individually visible through indument, longest mostly 1.5–2.7 mm. Staminate corollas 0.8–1.5 mm, lobes mostly 5. Cypselae narrowly obovoid, somewhat compressed, 0.7–1.2 mm.
Phenology: Flowering and fruiting late Mar–early Aug.
Habitat: Dry or seasonally moist, barren to wooded slopes, flats, often disturbed sites (foot paths, road beds, burns), sometimes near vernal pools toward s
Elevation: 0–2100 m
B.C., Calif., Idaho, Oreg., Wash., Mexico (Baja California).
Psilocarphus tenellus is relatively common in the Californian Floristic Province from northwestern Baja California to southwestern Oregon; northward it is scattered to northern Idaho and Vancouver Island, British Columbia. It has been of conservation concern in Canada (J. M. Illingworth and G. W. Douglas 1994b).