Erect biennial. Stems hispid, hollow, grooved, reddish purple blotched and spotted, particularly toward base, up to 350 cm high and 10 cm diam. Basal lvs moderately hispidulous below, sparsely above, pinnately 3-foliolate, petiolate; leaflets ovate to ovate-lanceolate, deeply ternately or pinnately lobed and irregularly double serrate, up to 50-(100) cm long; lobes usually acute to acuminate; stem lvs similar to basal, with petiole often reduced to sheathing part only; petioles reddish purple blotched and spotted. Umbels (20)-30-60 cm diam.; rays (20)-50-70-(100), the primary umbels > 50-rayed; bracts usually c. 12, linear, 10-15 mm long; bracteoles 8-12, linear, up to 15 mm long. Fls numerous, white; outer fls irregular and up to 15 mm diam. Fr. glabrous, ovate-elliptic, light brown, c. 10 mm long; vittae conspicuous, 0.5-1 mm wide at base.