Habit: Ricinus communis can vary greatly in its growth habit and appearance. It is a fast-growing shrub that sends out suckers. It can reach the size of a small tree, around 12 m (39 ft), but it is not cold hardy.
Root: It has a tap root.
Stem: The plants are multi-stemmed. Stems are covered with a white powder and they are hollow inside. The stems produce clear, watery sap when cut.
Leaves: The glossy leaves are 15–45 cm (6–18 in) in length, long-stalked, alternate and palmate with five to twelve deep lobes with coarsely toothed segments.
Flower: The flowers lack petals and are unisexual (male and female) where both types are borne on the same plant in terminal inflorescences of green or, in some varieties, shades of red. The male flowers are numerous, yellowish-green with prominent creamy stamens. The female flowers, borne at the tips of the spikes (that lie within the immature spiny capsules), are relatively few in number and have prominent red stigmas
Fruit: The fruit is a spiny, greenish to reddish-purple capsule containing large, oval, shiny, bean-like, highly poisonous seeds with variable brownish mottling.
Seed: Castor seeds have a warty appendage called the caruncle, which is a type of elaiosome. Elaiosomes are fleshy bits that hold fats and proteins. The caruncle promotes dispersal of the seed through ants.
Pollinators: Honey bees help in pollination of the castor plant. Pollen is mainly shed in the morning and flowers are wind-pollinated. They are capable of self- and cross-pollination.
Visiting Insects: Ricinus communis is the host plant of the Common Castor Butterfly, the Eri silkmoth), and the Castor Semi-Looper Moth). It is also used as a food plant by the larvae of some other species of Lepidoptera, the Nutmeg.
Seed Dispersal: The fruit bursts and throws the seed out which is then dispersed by ants who are attracted to the caruncle of the castor seed.
Where they grow: Castor is indigenous to the southeastern Mediterranean Basin, Eastern Africa, and India, but is widespread throughout tropical regions.
Medicinal: Castor seed is the source of castor oil, which has a wide variety of uses. The seeds contain between 40% and 60% oil that is rich in triglycerides, mainly ricinolein.
The seed also contains ricin, a water-soluble toxin, which is also present in lower concentrations throughout the plant. Castor oil was given to school children when they had upset stomachs.
In case of muscular injury without bleeding, leaf paste with mustard oil is applied on the affected area; leaf paste is applied on head to relieve headache. The oil is used as an anti-dandruff aid.
Warning: The chemical Ricin found in the castor seed is very poisonous. It must be used with caution. Leaves boiled with maize grain is used as a rat killer.