Cap 5-15 cm broad, conic with an incurved margin and pointed umbo, becoming planoconvex, the disc then sometimes shallowly depressed but still umbonate; in age the margin wavy, fluted to upturned; surface moist, hygrophanous, smooth, ochraceous-brown, buff-brown to dingy tawny-brown, fading overall at maturity; flesh thin, pallid to cream; odor and taste mild.
Gills adnexed, close, moderately broad, cream, in age cream-buff, the edges occasionally discoloring brown.
Stipe 4.5-13 cm tall, 1.3-2.5 cm thick, more or less equal, cartilaginous, striate, sometimes flattened, to furrowed, cottony mycelium at the base, the latter continuing as a root-like projection; surface pruinose, cream to dingy-buff; flesh pale-buff, fibrous; veil absent.
Spores 4.5-6 x 2.5-3 µm, elliptical, smooth, amyloid; spore print white.
Solitary to scattered under redwood; fruiting from early to mid-winter.
Caulorhiza umbonata is one of the few medium to large mushrooms that fruits under coast redwood (Sequoia sempervirens). The conic, when young, yellowish-brown cap with a pointed umbo, and pseudorhiza which extends deep into the substrate make it an easy species to identify.