Herbs erect, often single-stemmed but sometimes bushlike or treelike, 2-5(-10) m tall; younger parts glaucous, whole plant often reddish or purplish. Stipules connate, 2-3 cm; petiole 20-40 cm; leaf blade palmately 7-11-lobed, 30-50(-100) × 30-50(-100) cm, margin serrate. Inflorescence to 30 cm. Male flowers: pedicels 5-17 mm; calyx lobes 5-8 × 3-5 mm; stamens 7-8 mm. Female flowers: pedicels 5-10 mm; sepals ca. 5 mm; styles 2-5 mm. Fruiting pedicel to 45 mm; capsule ellipsoid or ovoid, 1.5-2.5 cm, echinate, spines to ca. 5 mm, sometimes smooth. Seed 7-12 mm, grayish, silvery, or beige with darker markings; caruncle depressed-conical, 2-3 mm wide. Fl. Jun-Sep, or Jan-Dec.

The seeds yield castor oil, used medicinally and as an industrial lubricant. The seeds are highly toxic.

Cultivated, ruderal weed, sometimes naturalized in riverbeds; below 100-500(-2300) m. Throughout China [cultivated worldwide].