Actinomeris longifolia A. Gray, Smithsonian Contr. Knowl. 5(6): 89. 1853

Plants 60–150+ cm (perennating bases ± erect, internodes not winged). Leaves all or mostly opposite (distal sometimes alternate); blades ± lance-linear (lengths 10–15 times widths), 9–12(–20+) × 0.6–1.2(–1.5+) cm, bases rounded, margins obscurely toothed to subentire, apices ± attenuate, faces ± scabrellous. Heads borne singly or 3–5+ in loose, corymbiform arrays. Involucres ± hemispheric to saucerlike, 11–15+ mm diam. Phyllaries 18–24+ in 2–3 series, ± erect to spreading, linear to lance-linear, 5–15+ mm. Ray florets 12–13; laminae 15–25+ mm. Disc florets 60–100+; corollas yellow. Cypselae dark brown, oblanceolate to elliptic, 7 mm, faces glabrous; pappi 0–0.5 mm. 2n = 34.

Flowering (Jul–)Sep–Oct. Rocky slopes; 1500–2400 m; Ariz., N.Mex.; Mexico (Chihuahua, Durango).