Erect, sometimes dichotomously branched annual herb, 30-120 cm. Leaves alternate, unpleasantly scented when crushed, ovate to rhombic-ovate, up to 16 × 12 cm, thinly textured, almost hairless to pubescent, particularly near the base; base often decurrent into the petiole; margin with almost lobe-sized triangular teeth. Flowers solitary in the forks of the branches or axillary. Calyx long and tube-like, up to 3.5 cm long, 5-angled with ovate to triangular-lanceolate unequal apical lobes, 2.5-7 mm long. Corolla white to pale yellowish, rarely pale blue, 4-7 cm long, slightly 5-lobed with narrow acuminate tips. Fruit erect, ovoid-ellipsoid, up to 8 × 6 cm (including spines), covered in robust unequal, narrowly conical spines, up to 2.5 cm long, purple-green to brownish when ripe, regularly dehiscent. All parts of the plant are poisonous.