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Castor Bean Ricinus communis

 

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Castor Bean, female flowers above, male flowers below
credit: tonrulkens (Ton Rulkens)/CCSA

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Family: Euphorbiaceae, Spurge view all from this family



Description The castor oil plant, Ricinus communis, is indigenous to the southeastern Mediterranean Basin, Eastern Africa, and India, but is widespread throughout tropical regions, and widely grown elsewhere as an ornamental plant). In areas with a suitable climate, castor easily escapes cultivation and can often be found on wasteland. 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 cold hardy. It is the only species in the genus Ricinus. All parts of the plant are toxic.

The castor oil plant can vary greatly in its growth habit and appearance. The variability has been increased by breeders who have selected a range of cultivars for leaf and flower colours, and for oil production.

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 seed contains the toxin ricin, which is also present in lower concentrations throughout the plant.

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. In some varieties they start off dark reddish purple or bronze when young, gradually changing to a dark green, sometimes with a reddish tinge, as they mature. The leaves of some other varieties are green practically from the start, whereas in yet others a pigment masks the green colour of all the chlorophyll-bearing parts, leaves, stems and young fruit, so that they remain a dramatic purple-to-reddish-brown throughout the life of the plant. Plants with the dark leaves can be found growing next to those with green leaves, so there probably is only a single gene controlling the production of the pigment in some varieties at least. The stems (and the spherical, spiny seed capsules) also vary in pigmentation. The fruit capsules of some varieties are more showy than the flowers.

The flowers are borne in terminal panicle-like inflorescences of green or, in some varieties, shades of red monoecious flowers without petals. 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, born at the tips of the spikes, have prominent red stigmas.

The fruit is a spiny, greenish (to reddish-purple) capsule containing large, oval, shiny, bean-like, highly poisonous seeds with variable brownish mottling. Castor seeds have a warty appendage called the caruncle, which is a type of elaiosome. The caruncle promotes the dispersal of the seed by ants (myrmecochory).


Warning Seeds contain toxic substances, and a single seed can be fatal if eaten. Leaves can cause skin irritation. Sensitivity to a toxin varies with a personís age, weight, physical condition, and individual susceptibility. Children are most vulnerable because of their curiosity and small size. Toxicity can vary in a plant according to season, the plantís different parts, and its stage of growth; and plants can absorb toxic substances, such as herbicides, pesticides, and pollutants from the water, air, and soil.


Habitat Cities, suburbs & towns, Scrub, shrub & brushlands, Fields.


Range Great Lakes, California, Plains, Southeast, Mid-Atlantic, Southwest, Texas, Florida, Eastern Canada, New England.


 

 

 

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