Erect biennial; stems glabrescent, grooved, with prickles on ridges especially above, becoming hollow, up to c. 2 m tall. Basal lvs glabrescent, elliptic-oblong, crenate but not lobed, narrowed to winged petiole, up to 40 cm long; prickles mostly on veins, especially on midvein of lower surface. Cauline lvs similar to basal but smaller, becoming sessile, lanceolate-triangular, the opposite pairs connate at base; uppermost lvs usually entire. Heads terminal, ovoid-cylindric at flowering, elongating to up to 9 cm long and becoming cylindric at fruiting; corolla pale purple to pinkish purple. Involucral bracts unequal, linear, curved upwards, the longest often > head at least at flowering, armed with prickles. Receptacular scale with straight or slightly recurved, flexible spine > floret. Achene brown, 4-angled and sulcate, 4-5 × 1-1.5 mm.