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.