The Castor Oil Plant is an annual shrub with a softly woody stem growing up to 4 metres high. The shiny, dark green or reddish leaves are paler below and star-shaped with serrated margins. The flowers are held above the leaves on stalks with the uppermost flowers being reddish and lower flowers cream. These are followed by green, brown or reddish, three-lobed capsules covered with soft spines. The entire plant is poisonous.