Rosilla

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).