Erect annual or short-lived perennial herb, up to 150 cm. Leaves alternate to sub-opposite triangular-ovate, up to 17 cm long, upper surface wrinkled and with scattered bristles, somewhat more hairy below; base decurrent down the long petiole. Flowers in curled elongating inflorescences, eventually up to 36 cm long, white, rarely mauve or blue. Fruits deeply bilobed with diverging beaked lobes, c. 4 × 4 × 2.5 mm, almost hairless.