Annuals, 10-30(-40) cm (tap­roots often twisted). Herbage (sometimes purple-tinged) glabrous. Stems usually 1 (freely branching upward). Leaves equally distributed; petiolate; blades ovate to obovate, 2-6 × 0.5-2(-4) cm, bases tapered, margins coarsely lobed or irregularly dentate (mid and distal leaves similar, bases expanded, truncate to cordate, clasping, 1-2 cm across). Heads 3-10 in loose, cymiform arrays. Calyculi of 3-5+ lance-linear bractlets. Phyllaries ± 8 or ± 13, 6-7 mm, tips green. Ray florets 0 or 1-3+; corolla laminae 0.1-1 mm (little expanded, barely, if at all, surpassing phyllaries; sometimes laminae 0 and heads perhaps technically disciform). Cypselae hairy. 2n = 40. Flowering spring. Sandy or rocky washes, desert flats; 100-700 m; Ariz., Calif., Nev.; Mexico (Sonora). Senecio mohavensis is similar to S. flavus (Decaisne) Schultz-Bipontinus of the Mediterranean region and southwest Asia, which raises phytogeographic questions (cf. A. Liston et al. 1989; Liston and J. W. Kadereit 1995; M. Coleman et al. 2001). The last cited study showed that a previously recognized variety of S. flavus is more closely related to S. mohavensis than to S. flavus and a new combination was made: S. mohavensis subsp. brevifolius (Kadereit) M. Coleman.

Plant: Annual 1-4 dm, from short, often twisted taproot, much-branched upward, glabrous, often purplish; stems generally 1-few per rosette Leaves: alternate, lower blades 2-6 cm (petiole poorly defined), (ob)ovate, unevenly dentate to lobed; upper blades clearly clasping INFLORESCENCE: primary inflorescence a head, each resembling a flower; heads radiate or disciform, 3-10; involucre cylindric to hemispheric; main phyllaries ± 8, sometimes 13, 6-7 mm, tips green Flowers: Ray flowers few, inconspicuous; ligules short, ± = phyllaries, generally yellow to orange; Disk flowers < 40; corolla generally ± yellow; style tips truncate to obtuse, generally hair-tufted Fruit: achenes, soft-hairy, cylindric; ribs shallow, often stiff-hairy; pappus of thin, minutely barbed deciduous bristles ± = fruit body Misc: Sandy washes, flats; < 1000 m.; Mar-May References: Jepson Maunual, Arizona Flora, ASU specimens