Colorado Feverfew

Perennials, 1–2 cm (underground caudices 2–5+ cm, branched; plants cespitose or forming mats). Leaf blades oblanceolate to spatulate, 5–18+ × 1–2(–4+) mm, margins entire, faces strigilloso-sericeous (gray) and obscurely gland-dotted. Heads radiate, borne singly. Peduncles 0–4 mm. Phyllaries: outer 5 ± ovate, 2.5–3 mm, inner 5 ± orbiculate, 3–4+ mm. Pistillate florets 5; corolla laminae oval to elliptic, 1–2 mm, retuse. Disc florets 15–25+. Cypselae oblanceoloid to pyriform, 3.5–4 mm; pappus-like enations 2, erect to spreading, ± subulate, 0.5–1 mm (a third, ± subulate element sometimes at apex of adaxial face). 2n = 36, 72.

Parthenium alpinum (Nuttall) Torrey & A. Gray var. ligulatum M. E. Jones, Contr. W. Bot. 13: 16. 1910