Annual herb to 1 m high. Leaves mostly 8–14 cm long, broad-ovate, margin lobed and often wavy. Sepals to 3.5 cm long. Capsule elliptic, 2–4.5 cm long, robust.
Distinguished by white flowers 4–6 cm long, stigma below anthers; capsule, usually with 40–60 stout spines, on straight stalk; seeds brown, grey or black, 4–5 mm long.