Erect annual. Stems densely hairy above but glabrous or sparsely hairy near base, solid, striate, 20-60-(100) cm high, sometimes purple tinged; hairs deflexed. Basal lvs densely hairy above and below, 2-pinnate, petiolate; ultimate segments ovate to lanceolate, pinnatifid and serrate, 15-45 mm long, sessile or shortly petiolulate; stem lvs similar to basal, but 1-pinnate or pinnately 3-foliolate toward apex with less divided segments. Umbels 1-4-(5) cm diam., long-pedunculate, usually terminal; rays (2)-3-9, 5-20-(30) mm long; bracts 0-1, linear; bracteoles 5-6, linear. Fls few to numerous, white or tinged pink, c. 2 mm diam., irregular. Fr. ovoid, 3.5-4.5 mm long; all mericarps spinous; spines curved upward, thickened at tip.