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.
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.
FNA 2006, Kearney and Peebles 1969, McDougall 1973, Heil et al. 2013, Allred and Ivey 2012, Correll and Johnston 1970
Duration: Perennial Nativity: Native Lifeform: Subshrub General: Subshrubs, to 100 cm tall or more, from woody taproots; stems several in clumps, arching to erect, not branching much; herbage can be glabrous or lanate-tomentose. Leaves: Alternate along the stems, sessile or obscurely petiolate; blades narrowly linear to filiform or pinnately divided into linear-filiform segments up to 35 mm long; fascicles of several small leaves sometimes borne in the axils of larger leaves. Flowers: Flower heads showy, yellow, and radiate, in large showy arrays; involucres cylindrical to hemispheric, 10-15 mm high, often with 3-5 calyculi (bractlets just below the involucre) half the length of the phyllaries or longer; phyllaries (bracts of the involucre) 13-21 in a single series, linear, 8-9 mm long, with green or black tips; ray florets 8-21 per flower head, the laminae (ray petals) 10-15 mm long, yellow; disc florets yellow. Fruits: Achenes to 4 mm long, terete, ribbed and densely canescent with small, coarse, stiff hairs; topped with a pappus of soft, silvery-white, capillary bristles, 7-8 mm long. Ecology: Found on dry plains, slopes, mesas, and along washes, from 2,500-7,500 ft (762-2286 m); flowers most of the year. Distribution: CA to KS, OK and TX; south to MEX. Notes: This is a common and widespread Senecio throughout the Southwest. FNA recognizes 3 intergrading varieties, though it notes that full understanding of the varieties will require more thorough knowledge of the species in Mexico. Var. flaccidus is present from Arizona eastward to Texas and Kansas, has densely white-hairy (tomentose) stems and leaves, and usually lacks calyculi (the small set of bractlets subtending the flower heads). Var. douglassii is on the west slope of the Sierras and westward in California and Baja Calif., is more or less grayish-tomentose, and has calyculi. Var. monoensis is present on the east slope of the Sierras and eastward throughout the species' range; it is nearly hairless and has calyculi. When using older texts to key your plants, use the synonym Senecio longilobus. Kearney and Peebles note that this species is highly poisonous to cattle and horses, causing lesions to the liver. Ethnobotany: This species was known to be toxic but had a variety of medicinal uses; it is a strong laxative and was used internally to treat stomach and kidney trouble; it was used externally as an infusion or salve to treat infected sores and cuts, sore muscles, acne, and skin diseases; the plant was used as a broom, and the herbage was added to bedding as a bug repellent; the plant was also used ceremonially. Etymology: Senecio is from the Latin senex, old man, which refers to the gray hairs on the seeds; flaccidus means weak or drooping and may refer to the arching stems. Synonyms: Senecio douglassii, Senicio longilobus Editor: LCrumbacher 2011, AHazelton 2017