Rock tansy

Tanacetum capitatum (Nuttall) Torrey & A. Gray

Perennials, 5–20 cm (cespitose, bases sometimes woody). Stems erect, ± tomentose. Leaves mostly basal; blades (± cuneate, 8–20 mm) usually 1–2-pinnati-palmately lobed (ultimate lobes ± linear), faces ± tomentose. Heads usually 8–20 in tight, capitate arrays (1–1.3 cm across), sometimes with solitary heads proximal to main arrays. Involucres (2–)3–4 mm. Phyllaries 5–8, tomentose. Receptacles glabrous. Cypselae 1–2 mm (3–5-ribbed, apices with thickened rims, faces glabrous or sparsely gland-dotted).

Flowering May–Jul. Dry, rocky hills; 1500–2400 m; Colo., Mont., Utah, Wyo.