Subshrubs, 20-40 cm (taproots forming woody crowns). Herbage closely, unevenly lanate-floccose, glabrescent. Stems usually multiple (strict or nearly so, arching-erect). Leaves (often recurved and thickish-turgid) concentrated distally on stems; sessile or obscurely petiolate; blades narrowly linear to filiform (2-7 cm × 1 mm), bases ± linear, margins entire. Heads 3-10 in corymbiform arrays (involucres weakly campanulate). Calyculi 0 or of 3-5 bractlets (lengths less than ¹ / 2 phyllaries). Phyllaries ± 13, 5-8 mm, tips green or minutely black. Ray florets usually ± 8, rarely 0; corolla laminae 5-10 mm. Cypselae glabrous.

Flowering fall (perhaps spring-summer). Open sites, gypseous soils; of conservation concern; 800-1500 m; N.Mex., Tex.

Senecio warnockii is infrequently collected; additional study may show it to be an edaphic phase of S. flaccidus. The restriction to gypseous soils and the gross aspect combine to make it distinctive.