Subshrubs or shrubs, (20-)40-150 cm (taproots woody). Herbage sparsely hairy, unevenly glabrate (usually with persistent tomentum in leaf axils and on abaxial leaf faces). Stems usually multiple (arching upwards). Leaves evenly dis­tributed (proximal withering before flowering); sessile or obscurely petiolate; blades ± oblong or elliptic, (4-)6-10(-12) × 1.5-3 cm (1-2-pinnatifid, lobes ± linear, 1-2 mm wide), bases ± linear, ultimate margins entire. Heads 4-12 in cymiform arrays (involucres campanulate, 8-15 mm diam.). Calyculi 0 or of 1-3+ (inconspicuous) bractlets. Phyllaries (± 13) ± 21, (5-)6-8 mm, tips minutely black. Ray florets ± 13; corolla laminae 8-10 mm. Cypselae hairy. 2n = 40.

Flowering spring. Ocean bluffs, open hillsides; of conservation concern; 0-500 m; Calif.; Mexico (Baja California).

Senecio lyonii is known from the Channel Islands (off the coast of southern California) and south.