Castor oil plant

The castor oil plant, Ricinus communis, is a plant species of the Euphorbiaceae and the sole member of the genus Ricinus and of the subtribe Ricininae. Its seed is the castor bean which, despite its name, is not a true bean.

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. They also contain ricin, a poison, which is also present in lower concentrations throughout the plant.

The toxicity of raw castor beans is well-known, and reports of actual poisoning are relatively rare. Children could conceivably die from as few as three beans; adults may require eight or more. As an example of the rarity of castor bean poisoning, in recent years there have only been two cases reported in all of England, and in both the victims recovered uneventfully.

Castor seeds have been found in Egyptian tombs dating back to 4000 BC. Herodotus and other Greek travelers have noted the use of castor seed oil for lighting and body anointments.

Global castor seed production is around 1 million tons per year. Leading producing areas are India, China and Brazil. There are several active breeding programmes.

Nomenclature
The name Ricinus is a Latin word for tick; the seed is so named because it has markings and a bump at the end which resemble certain ticks. The common name "castor oil" likely comes from its use as a replacement for castoreum, a perfume base made from the dried perineal glands of the beaver (castor in Latin). It has another common name, Palm of Christ, or Palma Christi, that derives from castor oil's ability to heal wounds and cure ailments.

Habitat and growth
Although castor is probably indigenous to the southeastern Mediterranean region and Eastern Africa, today it is widespread throughout tropical regions. Castor establishes itself easily as an apparently "native" plant and can often be found on wasteland. It is widely grown as a crop in Ethiopia. It is also used extensively as a decorative plant in parks and other public areas, particularly as a "dot plant" in traditional bedding schemes.

Although monotypic, the castor oil plant can vary greatly in its growth habit and appearance. It is a fast-growing, suckering perennial shrub which can reach the size of a small tree (around 12 m), but it is not hardy. In areas prone to frost it is usually shorter and grown as if it were an annual: it can reach a height of 2–3 m in a year (if sown early, under glass, and kept at a temperature of around 20°Celsius until planted out ). The glossy leaves are 15–45 cm long, palmate, with 5–12 deep lobes and toothed margins. Their colour varies from dark green, sometimes with a reddish tinge, to dark reddish purple or bronze. The stems and the spherical, spiny seed pods also vary in pigmentation. The pods are more showy than the flowers (the male flowers are yellowish-green with prominent creamy stamens and are carried in ovoid spikes up to 15 cm long; the female flowers, borne at the tips of the spikes, have prominent red stigmas).

Selections have been made by breeders for use as ornamental plants: 'Gibsonii' has red-tinged leaves with reddish veins and pinkish-green seed pods; 'Carmencita Pink' is similar, with pinkish-red stems; 'Carmencita Bright Red' has red stems, dark purplish leaves and red seed pods; all grow to around 1.5 m tall as annuals. 'Impala' is compact (only 1.2 m tall) with reddish foliage and stems, brightest on the young shoots; 'Red Spire' is tall (2–3 m) with red stems and bronze foliage; 'Zanzibarensis' is also tall (2–3 m), with large, mid-green leaves (50 cm long) with white midribs. (Heights refer to plants grown as annuals.)

Castor is used as a food plant by the larvae of some Lepidoptera species including Giant Leopard Moth, Hypercompe hambletoni and The Nutmeg. It is a favourite food of the Tambourine Dove, Turtur tympanistria

Uses
Usage in ethnobotany The use of castor seed oil in India has been documented since 2000 BC for use in lamps and in local medicine as a laxative, purgative, and cathartic in UNANI, Ayurvedic and other ethnomedical systems.

Castor seed and its oil have also been used in China for centuries, mainly prescribed in local medicine for internal use or use in dressings.