The castor plant is a small annual plant. It ranges from 1 to 7 meters in height. It has well developed roots, with green and reddish stems which become hollow with age. The fruit is a spherical capsule with small grey seeds with brown spots.

Castor oil plant or castor bean plant, is the common name for a wind pollinated flowering plant, Ricinus communism, of the Euphorbiaceous family, characterized by large, palmate lobed leaves, flowers during most of the year in dense terminal clusters, with female flowers above the male flowers, and clusters of spiny, red to bronze fruit or seed capsules that contain seeds with intricate mottled designs. Castor seeds are the source of both the commercially important castor oil, which has medicinal and industrial uses, and the extremely poisonous ricin, which has been used as a biochemical agent.