It is an annual plant growing to 20โ75 cm tall, with a thick, but soft stem. The leaves are spirally-arranged, 2.5โ9 cm long and 1โ2.5 cm broad, with a deeply toothed margin. The flowers are pink, red, mauve, lilac, or white, and 2.5โ5 cm diameter; they are pollinated by bees and other insects, and also by nectar-feeding birds. The ripe seed capsules undergo explosive dehiscence.