Biennial glabrous taprooted herb, 50-150 cm tall; rootstock ± woody; stem erect, ribbed, hollow, simple or sparingly branched. Lvs simple, entire, with undulate margins. Basal lvs narrow-oblanceolate, cuneate, (3)-6-12-(25) × 0.5-1.5-(2.5) cm; cauline lvs linear to narrow-oblong, the lower cuneate, the upper more abruptly narrowed, 2-7-(10) × 0.2-1-(2) cm. Pedicels ascending, c. 1-2.5 mm long. Sepals 4, ovate. Petals (3)-4-(5), yellowish green; limb of posterior petal 4-8-lobed, of laterals and anterior entire or 4-lobed. Stamens 20-25; filaments persistent. Capsule cup-shaped, with sparsely tubercled lateral ridges, 3-5-(6) × 3-5-(6) mm long; carpels 3. Seeds brownish black, smooth, shiny, 0.8-1 mm long.