Herbs 5-50 cm tall, annual. Stem erect, usually divaricately branched; stem and branches densely setiferous. Leaves setiferous pubescent with multicellular hairs, pinnatilobed or pinnatifid, prominently reticulate-veined especially on abaxial side, margin spinose to spinosely toothed. Basal leaves petiolate; leaf blade oblong, ca. 30 × 8 cm, runcinate to pinnatifid, often withered at anthesis. Lower and middle stem leaves petiolate; petiole winged; leaf blade narrowly elliptic, decreasing in size upward, pinnatilobed or pinnatipartite, base attenuate; lobes triangular, narrowly elliptic-triangular, or narrowly elliptic. Upper stem leaves sessile, base amplexicaul and shortly decurrent onto stem. Uppermost leaves exceeding capitula. Capitula few to several, rarely 1, solitary at end of stem and branches, concealed by subtending leaves. Involucre ovoid, ca. 2 cm in diam. Phyllaries imbricate, in 4 or 5 rows; outer phyllaries ovate, ca. 10 × 5 mm, leaflike, apex acute and tipped with a 3-6 mm spine; middle phyllaries elliptic, elliptic-lanceolate, or lanceolate, ca. 15 × 3-6 mm, apex with a rigid pectinately divided spine; inner phyllaries broadly linear, ca. 20 × 2.5 mm. Sterile florets filiform. Corolla pale yellow. Achene cylindric, ca. 8 mm, conspicuously many ribbed, glabrous, apex with a denticulate rim. Outer pappus elements in 1 row, ca. 1 cm, rigid, scabridulous; inner pappus elements much shorter, ciliate to inconspicuously arachnoid. Fl. and fr. Jun-Jul. 2n = 22.
Annuals, to 60 cm. Stems often spreading or prostrate, usually branched throughout, usually reddish, ± loosely tomentose. Leaves mostly cauline, sessile and often short-decurrent or proximal tapering to winged petioles, blades lanceolate to oblanceolate, 6–25 cm, margins coarsely dentate or pinnately lobed, lobes and teeth armed with short, weak spines, faces sparsely to densely hairy with jointed multicellular hairs and slender cobwebby hairs, resin-gland-dotted. Heads disciform, borne singly, sessile, each subtended by involucre-like cluster of leaf-like bracts. Involucres ± spheric, 20–40 mm. Phyllaries in several series, tightly overlapping, outer ovate with tightly appressed bases and spreading spine tips, inner lanceolate, tipped by pinnately divided spines more than 5 mm. Florets many; corollas yellow, those of sterile florets linear, 3-lobed, not exceeding disc corollas, very slender, those of disc florets 19–24 mm. Cypselae cylindric, slightly curved, 8–11 mm, with 20 prominent ribs, tipped by a 10-dentate rim, glabrous, attachment scars lateral; pappi of 2 series of awns, outer 9–10 mm, smooth or ± roughened, inner 2–5 mm, roughened with short spreading hairs. 2n = 22.