Annuals, 20–50(–60+) cm (taproots relatively thin, twisted). Herbage (± turgid or subsucculent) unevenly villous-tomentose, glabrescent. Stems usually single, rarely clustered. Leaves progressively reduced distally (basal usually withering before flowering); petiolate (petioles winged); blades oblanceolate to spatulate, 4–7 × 1.5–3 cm, bases tapered, margins incised (distal leaves sessile, bractlike). Heads 6–10(–20) in cymiform arrays. Calyculi of 1–5+ linear to subulate bractlets (to 4 mm). Phyllaries ± 13, 6–7 mm, tips green. Ray florets ± 8 (± 13?); corolla laminae 5–6 mm. Cypselae usually hairy (especially on angles), sometimes glabrous. 2n = 40.

Flowering late summer–early fall. Talus slopes of greenish yellow ash tuff; of conservation concern; 900–1200 m; Oreg.

Senecio erterrae is in the Center for Plant Conservation’s National Collection of Endangered Plants.