Annual or biennial. Stem erect, branching above, finely grooved, glabrous or with patent coarse spinous bristles up to 3-4 mm long below, 50-150-(250) cm tall. Lvs glaucous; rosette and lower stem lvs tapering to base, with stiff hairs and spinous bristles especially on veins beneath, 5-30 × 2-12 cm, deeply runcinate-pinnatifid to undivided; margins finely dentate to bristly ciliate, usually sinuate. Upper lvs becoming glabrous, triangular to obovate to linear, sometimes triangularly 3-lobed at apex, with oblong amplexicaul auricles at base. Infl. diffusely paniculate. Capitula numerous, cylindric. Involucre 8-13 mm long; bracts imbricate, suberect to reflexed at fruiting; outermost bracts triangular to ovate, subacute, 1/4-⅓ length of innermost bracts; inner bracts lanceolate to linear, obtuse to acute. Florets c. 11/2× length of involucre; corollas erect to erecto-patent, yellow. Achenes pale brown to grey, sometimes dark-spotted, 5-9-ribbed on each face, obovate, flattened, finely spiny distally on ribs; body 2.5-3 mm long; beak pale, = body. Pappus fine, white.