Annuals, 10-80 cm (robust). Stems 1-25, usually purple-red-tinted proximally, sometimes throughout, often branched throughout, ± hairy. Leaves: blades simple or lobed (lobes 3-19+), ± hairy, gland-dotted; mid leaves lobed (lobes 5-11+, terminal lobes 0.3-1 mm wide). Heads 15-350+ per plant in paniculiform arrays. Peduncles 2-12 cm, sparsely hairy. Involucres subhemispheric to campanulate to ± urceolate, 6-10 × 7-12.5 mm. Phyllaries in 2 series, unequal; outer 8-13, basally connate ¹/4-¹/3 their lengths, obovate to oblanceolate, 3.5-5.2 mm, apices acuminate; inner 8-13, obovate, 3.8-5.9 mm, apices acuminate to acute. Ray florets 8-13; corollas yellow, 8.5-11 × 3-5.5 mm. Disc florets 50-150+; corollas 2.6-4.1 mm. Cypselae narrowly obpyramidal, 1.7-2.5 mm; pappi of 5-6 obovate, aristate scales 1.6-2.3 mm. 2n = 22, 24, 28, 30. Flowering (Feb-)Apr-Jun(-Aug). Roadsides, open flats, mesquite and creosote-bush flats, ditches and drainage areas, stream banks and bottoms; 60-1500 m; Ariz., Calif., Colo., Kans., N.Mex., Okla., Tex.; Mexico (Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, Sonora, Tamaulipas).

Plant: Annual 15-60 cm, soft-hairy, ± glabrous in age; stems erect, branched above Leaves: basal generally 0 at time of flower; cauline 1-5 cm, simple, alternate, divided into linear lobes 1 mm or less wide, dotted with sunken resin glands INFLORESCENCE: primary inflorescence a head, each resembling a flower; heads radiate, in flat-topped cyme; peduncles 2-15 cm; involucre generally 5-7 mm diam; outer phyllaries 3-5 mm, < inner phyllaries, thickened and fused at base Flowers: Ray flowers ± 8; ligules generally 1 cm or less, yellow, fading to cream and ± persistent on fruit; corolla yellow, fan-shaped, 3-5-lobed; Disk flowers: many; corolla 3-4 mm, yellow Fruit: ± 2 mm, obpyramidal, generally 5-angled, hairy; pappus scales 5, 2 mm, lanceolate, membranous Misc: Sandy flats near Colorado River; < 150 m.; Feb-May