Hymenoxys rusbyi (A. Gray) Cockerell

Perennials, 30–150 cm (poly­carpic, often with moderately branched, woody caudices). Stems 1–5(–15), usually purple-red-tinted proximally, branched distally, glabrous or ± hairy. Leaves: blades simple or lobed (lobes 3), glabrous, gland-dotted; mid leaves simple or lobed (lobes 3, terminal lobes 2–4 mm wide). Heads 50–250+ per plant, in corymbiform arrays. Peduncles 1–3.2 cm, glabrous or ± hairy. Involucres campanulate to urceolate, 6–8 × 6–7 mm. Phyllaries in 2 series, unequal; outer 7–9, basally connate ¹/4–¹/3 their lengths, lanceolate, 4.5–6 mm, apices usually rounded; inner 7–11, obovate, 3.5–4.5 mm, apices mucronate. Ray florets 6–8; corollas yellow, 4.5–8 × 2.5–5 mm. Disc florets 25–50+; corollas 2.7–3.2 mm. Cypselae narrowly obpyramidal, 2–3 mm; pappi usually of 5 obovate, sometimes aristate, scales 0.9–1.8 mm. 2n = 30.

Actinella rusbyi A. Gray, Proc. Amer. Acad. Arts 19: 33. 1883

Hymenoxys rusbyi (A. Gray) Cockerell, Bull. Torrey Club
31: 496. 1904.
Actinella Rusbyi A. Gray, Proc. Am. Acad. 19: 33. 1S83. Picradenia Rusbyi Greene, Pittonia 3: 271. 1898.
A short-lived perennial, with a thick root, scarcely cespitose ; stem 3-4 dm. high, glabrous or slightly puberulent, terete, fasciculately branched above, often purple-tinged; leaves mostly entire, rarely with 2 broad lobes, linear, the basal ones 8-20 cm. long, 2-4 mm. broad, glabrous; stem-leaves much shorter, all entire; heads numerous; peduncles 2-5 cm. long; involucre 5-6 mm. high, 6-7 mm. broad; outer bracts about 8, thick and rounded on the back, glabrate, united about one third their length, the free portions lanceolate, acute; inner bracts somewhat longer, ovate, acute, erose on the margins; ligules light-yellow, 6-7 mm. long, 2.5-3 mm. wide; disk-corollas 3 mm. long, densely glandular-puberulent; tube about 1 mm. long; achenes 3 mm. long, densely hirsute; squamellae cuneate to broadly ovate, almost triangular, truncate or blunt, scarcely 1 mm. long.
Type locality: Mogoflon Mountains, New Mexico. Distribution: Southwestern New Mexico.

Hymenoxys rusbyi is a North American species of flowering plant in the daisy family known by the common names Rusby's rubberweed or Rusby's bitterweed. It has been found only in the states of Arizona and New Mexico in the southwestern United States.

Hymenoxys rusbyi grows in open areas, generally at the edges of pine-oak forests at elevations of 1500–2500 meters (5000–8300 feet). It is a perennial herb up to 150 cm (5 feet) tall. One plant can produce sometimes as many as 250 flower heads in a branching, flat-topped array. Each head has 6–8 yellow ray flowers and 25–50 tiny yellow disc flowers.

Hymenoxys rusbyi là một loài thực vật có hoa trong họ Cúc. Loài này được (A.Gray) Cockerell mô tả khoa học đầu tiên năm 1904.