Perennials, (50–)60–100(–120) cm (caudices fibrous-rooted). Herbage sparsely floccose­­-to­me­ntose, unevenly glabrescent. Stems single. Leaves evenly distributed; petiolate; well-developed mid leaves: blades lanceolate to oblong,(8–)10–15(–18) × (2–)3–5(–9) cm overall, margins deeply dentate or irregularly pinnate-lobed to laciniate; distal leaves sessile, weakly clasping. Heads 8–20 in corymbiform arrays. Calyculi of 3–8+ linear to filiform bractlets (lengths ¹ / 2 – ³ / 4 + phyllaries). Phyllaries ± 13 or ± 21, 5–8 mm, tips green. Ray florets ± 8 or ± 13; corolla laminae 8–12(–20) mm. Cypselae glabrous.

Flowering late summer. Moist meadows, conifer-dominated sites; 1400–2700 m; Calif.

Senecio clarkianus grows on west slopes of the central and southern Sierra Nevada.