Annuals or perennials, 50-160 cm. Stems usually 1, branched distally, strongly winged, glabrous proximally, sparsely hairy distally. Leaves glabrous or sparsely hairy; basal blades oblanceolate to oblong-elliptic, entire; proximal and mid blades lanceolate to oblong-elliptic, entire; distal blades lance-linear, entire. Heads 4-20(-30) per plant, in paniculiform arrays. Peduncles (6-)9-17(-23) cm, sparsely to moderately hairy. Involucres globose to depressed globose, 9-15 × 9-17(-19) mm. Phyllaries (distinct or connate proximally) moderately hairy. Ray florets 0, or 13-15, pistillate, fertile; corollas yellow, 3.8-10 × 2-4 mm. Disc florets 300-500(-1000+); corollas yellow proximally, yellow to reddish brown to purple distally, (1.6-)1.9-2.7 mm, lobes 4(-5). Cypselae 1.2-1.9 mm, moderately hairy; pappi of 5-6 entire, aristate scales 0.4-1 mm. 2n = 58.

Flowering (Mar-)Jun-Aug(-Nov). Along streams, ditches, seepage areas, around ponds and lakes, forests, woodlands; 0-1200 m; Calif.; Mexico (Baja California).

Helenium puberulum may be of amphidiploid origin from hybridization between H. bigelovii (perennial, radiate, 2n = 32) and H. thurberi (annual, rayless, 2n = 26) (M. W. Bierner 1972).