Rosilla

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).

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.

Helenium puberulum DC. Prodr. 5: 667. 1836
Cephalophora decurrens Less. Linnaea 6: 517. 1831.
Helenium pubescens H. & A. Bot. Beech. Voy. 355. 1838. Not //. pubescens Ait. 1789.
Helenium californicum Link, Ind. Sem. Hort. Berol. 1840: 21. 1840.
? Helenium Rosilla Turcz. Bull. Soc. Nat. Mosc. 24': 186. 1841. Helenium mexicanum A. Cray, in Ton. Pacif. R. K. Rep. 4: 107. 1857. Not //. mexicanum II H
K. 1820. Helenium decurrens Vatkc, Ind. Sem. Ilort. Berol. 1875: App. 1875. Not Helenia decurrens
Moench. 1794. Heleniastrum puberulum Kimt/c, Rev. Gen. 342. 1891.
A stout annual; stem 5-10 dm. high, angled, puberulent, branched above; basal leaves oblanceolate, 1-2 dm. long, 3-4 cm. wide, puberulent, entire or denticulate; upper stemleaves linear-lanceolate, attenuate; peduncles 5-20 cm. long; bracts subulate, 8-10 mm. long, hirsute; ray-flowers pistillate; ligules yellow, 4-6 mm. long, 3-5 mm. wide; disk brownishyellow to purplish-brown, 12-18 mm. broad when mature; corollas 2.5-3 mm. long; tube a mere ring; throat elongate-campanulate; achenes fully 1.5 mm. long, hispidulous on the angles; squamellae 1 mm. long, ovate or lanceolate, awn-tipped.
Typk locality: California.
DISTRIBUTION: California and northern Lower California.

Helenium puberulum is a North American species of flowering plants in the daisy family known by the common name rosilla. It is native to California and Baja California, where it can be found in moist habitats such as riverbanks and meadows. It has also been found in Oregon, although these might possibly be naturalized populations.

Helenium puberulum is an annual or perennial herb sometimes as much as 160 cm tall though other times much smaller. Most of the leaves are on the lower part of the plant. Stems are winged, meaning that they have flaps of tissue running down the sides. One plant can produce as many as 30 flower heads in a branched array. The head is unusual in that the part covered by the disc florets is almost completely spherical rather than conical as in most other species of the genus. There can sometimes be over 1000 small disc florets in the head, each yellow at the bottom but brown or purple toward the tip. The 13-17 yellow ray florets are small and inconspicuous, pointing backwards down the flower stalk. Sometimes the ray florets are completely absent. The fruit is a hairy achene one to two millimeters long.