Parthenium alpinum

Perennials, 1-2 cm (underground caudices 2-5+ cm, branched; plants cespitose or forming mats). Leaf blades oblanceolate to spatulate, 6-18(-35) × 1-3(-4+) mm, margins entire, faces strigilloso-sericeous (gray) and obscurely gland-dotted. Heads ± disciform, borne singly. Peduncles 0-5(-30) mm. Phyllaries: outer 5-8 ± linear, 4 mm, inner 5-8 ± orbiculate, 4-5 mm. Pistillate florets 5-8; corolla laminae 0 (tubes ± compressed, obscurely 2-4-lobed). Disc florets 18-28+. Cypselae oblanceoloid, 4 mm (narrowly winged); pappus-like enations 2, erect to spreading, ± subulate, 0.5-1 mm (a third, ± subulate element sometimes at apex of adaxial face). 2n = 36.

Flowering May-Jul. Shale and calcareous outcrops, red clays; 1300-1700 m; Colo., N.Mex., Wyo.

Parthenium alpinum is in the Center for Plant Conservation´s National Collection of Endangered Plants.