Perennials, 8-40 cm; taproots deep, caudices swollen, (often covered with old leaf bases). Stems 1-3, erect, stout, branched from bases or beyond, hispid, tomentose, or tomentulose, sometimes stipitate-glandular distally. Leaves basal and cauline; petiolate; blades elliptic, runcinate, (5-)8-20 × 2-5 cm, margins pinnately-lobed to sinuously dentate (lobes broadly lanceolate, often dentate), apices acute or acuminate, faces gray-tomentose, sometimes stipitate-glandular. Heads 2-30, in loose corymbiform arrays. Calyculi of 6-8, lanceolate or linear, glabrate to tomentose bractlets 2-6 mm. Involucres cylindric, 11-19 × 5-10 mm. Phyllaries 7-13, lanceolate, 12-15 mm, (bases thickened, keeled, margins green, often scarious) apices acute or acuminate, abaxial faces gray-tomentose, sometimes setose (setae black or greenish) or stipitate-glandular, adaxial glabrous or with fine hairs. Florets 10-40; corollas yellow, 18-22 mm. Cypselae golden or dark brown, subcylindric, 6-10 mm, apices tapered (not beaked), ribs 10-18, strong and rounded; pappi yellowish white, 10-12 mm (bristles unequal). 2n = 22, 33, 44, 55, 66, 77, 88.
Crepis occidentalis is recognized by the old, brown leaf bases persisting on caudices, by stems, leaves, and phyllaries gray-tomentose, and by loose, corymbiform arrays with relatively few, relatively large heads. It is widespread and polymorphic. Some specimens have coarse setae or black, stipitate glands on the phyllaries in addition to the tomentose indument, the stipitate glands sometimes extending proximally on stems. Four intergrading subspecies were recognized by E. B. Babcock (1947). The sexual diploid forms are found in subsp. occidentalis and occur in northern California and adjacent Nevada. The other subspecies are polyploid and apomictic (Babcock).