Intermountain Rubberweed

Perennials, 20–50 cm (polycarpic; usually with moderately branched, woody caudices). Stems 1–5(–10+), green throughout or lightly purple-red-tinted proximally, branched distally, ± hairy. Leaves: blades simple or lobed (lobes 3), glabrous or sparsely hairy, gland-dotted (basal leaf bases sparsely, if at all, long-villous-woolly); mid leaves usually lobed (lobes 3, terminal lobes 2–5.5 mm wide), sometimes simple. Heads 5–50+ per plant, in paniculiform to corymbiform arrays. Peduncles (2.5–)4–7.5 cm, ± hairy. Involucres subhemispheric to hemispheric, 9–12 × 12–18 mm. Phyllaries in 2 series, unequal; outer 10–15, basally connate ¹/4–¹/3 their lengths (weakly keeled), lanceolate, 7.5–11 mm, apices acuminate; inner 13(–17), obovate, 5–8 mm, apices acuminate to mucronate. Ray florets 10–16; corollas yellow to yellow-orange, 17–31 × 5–11 mm. Disc florets 50–150+; corollas 3.5–5.5 mm. Cypselae narrowly obpyramidal, 2.5–3.5 mm; pappi of 5–7 obovate to lanceolate, aristate scales 2.5–4 mm. 2n = 30.

Picradenia helenioides Rydberg, Bull. Torrey Bot. Club 28: 21. 1901

Hymenoxys helenioides (Rydb.) Cockerell, Bull. Torrey Club
31: 4S1. 1904.
Picradenia helenioides Rydb. Bull. Torrey Club 28: 21. 1901. Dugaldia helenioides A. Nelson; Coult. & Nels. Man. 562. 1909.
A tall biennial; stem branched above, about 5 dm. high, finely puberulent; leaves rather firm, finely puberulent, 5-15 cm. long, 5-10 mm. wide, linear or narrowly linear-oblanceolate, some of the middle ones often parted into 3-5 linear divisions; heads corymbose; involucre somewhat tomentose, hemispheric, 8-9 mm. high and about 15 mm. broad; outer bracts 14-18, narrowly lanceolate, united only at the base, longer than the inner; ligules orange, about 10 mm. long and 3 mm. wide; disk-corollas 4 mm. long, sparingly glandular; tube 1 mm. long; achenes 3 mm. long, silky-hirsute; squamellae 3 mm. long, lanceolate, attenuate into an awn-point.
Type locality: Sangre de Cristo Creek, southern Colorado. Distribution: Known only from the type locality.

Hymenoxys helenioides is a North American species of flowering plant in the daisy family known by the common name intermountain rubberweed. It is native to Arizona, Utah, Colorado, and New Mexico in the western United States.

Hymenoxys helenioides is a perennial herb up to 50 cm (20 in) tall. One plant generally produces as many as 50 flower heads. Each head has 10–16 ray flowers and 50–150 disc flowers.