Linnaea 5: 161. 1830.
Subshrubs or shrubs, (30–)40–120+ cm (taproots forming woody crowns). Herbage glabrous or ± lanate-tomentose. Stems usually multiple (little branched, arching-erect). Leaves ± evenly distributed; sessile or obscurely petiolate; blades narrowly linear to filiform (or pinnatifid, the segments linear to filiform), 3–10(–12) cm, bases ± linear, ultimate margins entire or remotely toothed (fascicles of smaller leaves sometimes borne in axils of larger leaves). Heads (1–)3–10(–20+) in corymbiform or subcorymbiform clusters, often gathered in larger, showy arrays (involucres campanulate or cylindric). Calyculi usually of 3–5+ bractlets (lengths often to 1/2+ phyllaries), sometimes 0. Phyllaries ± 13 or ± 21+, 5–10(–12) mm, tips green or minutely black. Ray florets usually ± 8 or ± 13, sometimes ± 21; corolla laminae 10–15(–20) mm (mostly yellow, sometimes ochroleucous). Cypselae hairy. 2n = 40.
Ariz., Calif., Colo., Kans., N.Mex., Nev., Okla., Tex., Utah, Mexico.
Varieties 3 (3 in the flora).
The varieties of Senecio flaccidus are distinguished by morphologic tendencies and geography. The species occurs southward to central Mexico; a sound understanding of the infraspecific taxonomy must await revisionary studies that include the Mexican plants.
|1||Herbage usually tomentose (hairs whitish), sometimes unevenly glabrescent; bractlets of calyculi minute or 0; involucres cylindric or ± campanulate; phyllaries ± 13 or ± 21, 5–8+ mm||Senecio flaccidus var. flaccidus|
|1||Herbage ± tomentose, glabrate, or glabrous; bractlets of calyculi well developed (lengths mostly 1/3 – 1/2 phyllaries); involucres ± campanulate; phyllaries ± 21, 7–12 mm||> 2|
|2||Plants usually ± tomentose (usually with persistent, uneven grayish tomentum), sometimes unevenly glabrescent; California w of crests of Sierra Nevada and related ranges||Senecio flaccidus var. douglasii|
|2||Plants glabrate or glabrous; California deserts e of crest of Sierra Nevada and eastward||Senecio flaccidus var. monoensis|