Arizona Rubberweed

Hymenoxys subintegra grows mainly on the Kaibab Plateau north of the Grand Canyon in Arizona and in western Kane County, Utah.

Biennials or perennials, 30–60 cm (monocarpic; sometimes with sparingly branched, woody caudices). Stems 1(–5), green through­out or sometimes purple-red-tinted proximally, branched distally, usually densely sericeous. Leaves: blades simple or lobed (lobes 3), usually densely sericeous, gland-dotted; mid leaves simple or lobed (lobes 3, terminal lobes 1.8–3.5 mm wide). Heads 10–85+ per plant, in paniculiform to corymbiform arrays. Peduncles 3–9 cm, usually densely sericeous. Involucres hemispheric to campanulate, 8–10 × 10–13 mm. Phyllaries in 2 series, unequal; outer 10–14(–18), basally connate ¹/4–¹/2 their lengths, lanceolate, obovate, or ovate 5–7 mm, apices acuminate to acute; inner phyllaries 13–16(–22), obovate, 4–5 mm, apices mucronate. Ray florets 10–16; corollas yellow, 10–15 × 4.5–6.5 mm. Disc florets 50–100+; corollas 3.5–4 mm. Cypselae narrowly obpyramidal, 2.1–3 mm; pappi of 5(–6) obovate, aristate scales 2.5–3 mm. 2n = 30.

Actinea subintegra (Cockerell) S. F. Blake

Hymenoxys subintegra Cockerell, Bull. Torrey Club 31: 480
1904.
A perennial, with a tap-root and short thick caudex; stems solitary or few, about 2 dm. high, canescent; lower leaves linear, canescent, 5-6 cm. long, 2-3 mm. wide, entire; middle cauline leaves broader and usually with a few linear or lance-linear divisions; upper leaves linear and entire; heads several but inflorescence not flat-topped; involucre hemispheric, 5-6 mm. high, 10-12 mm. broad; outer bracts about 12, united one fourth to one third their length, carinate below, the free portions narrowly lanceolate and green, woolly; inner bracts broadly oval, short-acuminate; ligules deep-yellow, 8-9 mm. long; disk-corollas 3.2 mm. long; achenes 2.5 mm. long, silky; squamellae ovate-lanceolate, long-acuminate, nearly as long as the disk-corollas.
Type locality: Nagle's Ranch, Arizona. Distribution: Known only from the type locality.

Hymenoxys subintegra is a North American species of flowering plant in the daisy family known by the common name Arizona rubberweed. It has been found only in the states of Arizona and Utah in the southwestern United States. Many of the populations lie inside Grand Canyon National Park, others in Kaibab National Forest.

Hymenoxys subintegra grows in open areas, generally at the edges of forests at elevations of 2100–2800 meters (7000–9300 feet). It is a perennial herb up to 60 cm (2 feet) tall. One plant can produce 10–85 flower heads in a branching, flat-topped array. Each head has 10–16 yellow ray flowers and 50–100 tiny yellow disc flowers.