Castor oil plant

The castor oil plant, Ricinus communis, is a species of flowering plant in the spurge family, Euphorbiaceae. It belongs to a monotypic genus, Ricinus, and subtribe, Ricininae. The evolution of castor and its relation to other species is currently being studied. 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. The seed coat contains ricin, a toxin, which is also present in lower concentrations throughout the plant.

The toxicity of raw castor beans is well-known. Although as few as one bean can kill any human and four could kill a horse, reports of actual poisoning are relatively rare.

Castor seeds have been found in Egyptian tombs dating back to 4000 BC being used mostly to fuel lamps because of the slow burning oil. Herodotus and other Greek travelers have noted the use of castor seed oil for lighting, body ointments, and improving hair growth and texture. Cleopatra is reputed to have used it to brighten the whites of her eyes. The Ebers Papyrus is an ancient Egyptian medical treatise believed to date from 1552 BC. Translated in 1872, it describes castor oil as a laxative.

Global castor seed production is around 1 million tons per year. Leading producing areas are India (with over 60% of the global yield), China and Brazil. There are several active breeding programmes.

Another plant species, Fatsia japonica, looks similar to the castor oil plant and is known as the false castor oil plant.

Description

The glossy leaves are 15–45 centimetres (5.9–18 in) long, long-stalked, alternate and palmate with 5–12 deep lobes with coarsely toothed segments. 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 centimetres (5.9 in) long; the female flowers, borne at the tips of the spikes, have prominent red stigmas).

Terminating stems are panicle-like inflorescences of green monoecious flowers, the stalked female flowers above the male flowers below, both without petals.

The fruit is a spiny, greenish capsule with large, oval, shiny, bean-like, highly poisonous seeds with variable brownish motling.

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 indigenous to the southeastern Mediterranean Basin, Eastern Africa, and India, 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. It was used in Edwardian times in the parks of Toronto, Ontario, Canada. Of the red and white variety, the red is seen as an ornamental plant, the white is used medicinally.
Castor oil seed output in 2006

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 metres/39 feet), but it is not hardy. However it grows well outside, at least in Southern England, and the leaves do not appear to suffer frost damage in sheltered spots, where it remains evergreen. In areas prone to frost it is usually shorter and grown as if it were an annual. If sown early, under glass, and kept at a temperature of around 20 °C (68 °F) until planted out, the castor oil plant can reach a height of 2–3 metres (6.6–9.8 ft) in a year.

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 metres (4.9 ft) tall as annuals. 'Impala' is compact (only 1.2 metres/3.9 feet tall) with reddish foliage and stems, brightest on the young shoots; 'Red Spire' is tall (2–3 metres/6.6–9.8 feet) with red stems and bronze foliage; 'Zanzibarensis' is also tall (2–3 metres/6.6–9.8 feet), with large, mid-green leaves (50 centimetres/20 inches long) that have white midribs. (Heights refer to plants grown as annuals.)

Plant-animal interactions

Ricinus communis is the host plant of the Common Castor butterfly (Ariadne merione) and the Castor Semi-Looper moth (Achaea janata). It is also used as a food plant by the larvae of some other species of Lepidoptera, including Hypercompe hambletoni and the Nutmeg (Discestra trifolii).

Among birds, it is a favourite food of the Tambourine Dove (Turtur tympanistria).

Castor beans are very toxic.

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. Traditional Ayurvedic medicine considers castor oil the king of medicinals for curing arthritic diseases.

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.

Castor oil is also the source for undecylenic acid, a natural fungicide.

The oil is known to have been used as an instrument of coercion by the paramilitary Blackshirts under the regime of Italian dictator Benito Mussolini. Dissidents and regime opponents were forced to ingest the oil in large amounts, triggering severe diarrhoea and dehydration, which could ultimately cause death. This punishment method was originally thought of by Gabriele D'Annunzio, the Italian poet and Fascist supporter, during the First World War.

It was used in rituals of sacrifice to please the gods in early civilizations.

In Brazil, castor plants are abundant. The "fruits" are used by children as slingshot balls. Mamonas, as the fruits are called, serve perfectly as projectiles for slingshots since they have the right weight, size and hardness. Mamona oil is now being used to produce biodiesel in poor rural areas of the country.