Proc. Amer. Acad. Arts 17: 220. 1882.
Subshrubs (monocarpic?), (10–)20–100 cm (taproots woody). Herbage glabrous or with tufts of white hairs in leaf axils. Stems usually 1 (branching distally, unevenly reddish, usually somewhat lax). Leaves evenly distributed; petiolate (proximal) or sessile; blades lanceolate to lance-linear, 3–10+ × (0.5–)1–2 cm, bases tapered (or auriculate), margins (sometimes revolute) unevenly dentate to subentire (mid and distal leaves similar, smaller, bases expanded, ± truncate to cordate, clasping). Heads 4–12 in loose, corymbiform arrays. Calyculi of 3–5+ linear to subulate bractlets (to 1.5 mm). Phyllaries ± 21, (4–)5–8 mm, tips often with minute black dots. Ray florets usually ± 8 or ± 13, rarely 0; corolla laminae 8–10 mm. Cypselae hairy.
Phenology: Flowering late winter–early summer.
Habitat: Rocky sites in deserts
Elevation: 500–1000 m
Some young or depauperate specimens of Senecio lemmonii from northern Mexico resemble S. californicus, which occurs farther to the west in California and Baja California. Whether or not there is a relationship between the two is undetermined.