Perennials, (30-)40-100(-150) cm, cespitose; short-rhizomatous. Stems 1-5+, ascending to erect, strigose, villous, or lanate, especially distally. Leaves (grayish green) thin to firm, margins entire, apices acute, faces strigose; basal withering by flowering, petiolate, blades narrowly oblanceolate, 50-100(-150) × 4-12(-15) mm, bases attenuate, margins scabrous to ciliate; proximalmost cauline often withering by flowering (often with tufts of leaves in axils), sessile, blades linear to narrowly oblong, 30-70(-100) × 4-8(-10) mm, bases attenuate or cuneate, apices acute; distal sessile, blades 15-80 × 2-8(-10) mm, bases cuneate, sometimes auriculate. Heads (3-50+) in narrowly paniculiform arrays, branches 2-10(-20) cm. Peduncles densely short-strigose, bracts 1-6, linear-oblong, strigose. Involucres campanulate, 4-7 mm. Phyllaries in 3-6 series, narrowly oblanceolate or linear (outer) to linear (inner), unequal, bases indurate, margins entire, narrowly scarious, ciliate, green zones obovate to elliptic, apices obtuse, mucronulate, faces usually strigose. Ray florets 15-40; corollas pale violet, laminae 8-12(-15) × 1-1.5(-2) mm. Disc florets 25-70+; corollas yellow, 4-6 mm, lobes triangular, 0.4-0.8 mm. Cypselae brown, cylindric to obovoid, not compressed, 1.5-3 mm, ribs 5-8, faces hairy; pappi whitish, 4-6 mm. 2n = 36.

Flowering Aug-Nov. Dry open grasslands and meadows, often near springs; of conservation concern; 0-1700 m; Calif.

Symphyotrichum defoliatum is known from the San Gabriel and San Bernardino mountains, and from the Peninsular Ranges, southern California.