Caster Bean Information


The castor oil plant (Ricinus communis) is a single genus distantly related to the family Euphorbiaceae that includes cassava plants, rubber trees and poinsettias. The "bean" is actually a seed. The seeds also contain ricin, one of the most deadly natural poisons in existence. The oil extracted from the seeds is useful for numerous commercial applications.

Seed Poison

Ricin, the deadly natural poison in castor seeds, is an enzyme that inactivates a critical ribosome, the part of a cell that makes proteins from amino acids. Ricin is water soluble. If seeds are swallowed without being chewed, which would damage the coat and release the toxin, they pass harmlessly through the digestive system. The symptoms of ricin poisoning are abdominal pain, diarrhea and vomiting, following by a decrease in blood pressure and urine and severe dehydration. The ricin in two to three seeds is enough to kill a child; four to six seeds will kill an adult. Victims of ricin poisoning may die within three to five days, but if they're treated they usually recover. After the oil has been extracted from castor beans, they are heated for 20 minutes at 284 degrees Fahrenheit to kill the ricin. They are then added as nutrients to food for sheep and livestock.

Oil Uses

Castor oil is extracted from seeds by pressing them, so there is no ricin in castor oil. Castor seeds are the only commercial source of hydroxyl-fatty acid whose properties make it useful for cosmetics, plastics, coatings, paint, soaps and skin medications. It added to diesel fuel to help reduce sulfur emission. Processed castor oil is used as a substitute for cocoa butter in the manufacture of chocolate bars.

Origin and Spread

The invasive castor plant originated in Africa, growing as a shrub or tree beside tropical streams, rivers and bottomlands. It is now found in parts of Australia, the Pacific Islands and 27 states. It is grown commercially for its seed oil in several countries, including India, plus California, Kansas, Missouri, Oklahoma and Oregon. In the south it has spread along the sides of roads, in barnyards, dumping grounds and streambeds.

Cultivation and Seeds

The castor oil plant is capable of growing 40 feet tall. It is grown ornamentally because of its green, star-shaped leaves that can grow to 3 feet long. Hybrid cultivars of castor bean plants produce bright purple or red foliage. It is a perennial in tropical areas but can be grown as an annual in temperate growing zones. The inconspicuous female flowers yield ½- to 1-inch long capsules that have soft spines. The flowers are commonly green but are red or pink in hybrid varieties. Mature capsules open to reveal three smooth, colorful seeds that are a muted mosaic of black, brown, gray, maroon, yellow-brown and white.


Remove the buds of castor oil plants grown as ornamentals before they are allowed to produce flowers and seeds. Castor seeds have been known to kill cattle, rabbits, horses, ducks and other animals. It only takes seven seeds to kill a pig, but 80 to kill a duck. The colorful castor seeds are sometimes used as beads. Drilling seeds for beads is dangerous; it can release ricin.

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About this Author

Richard Hoyt, the author of 26 mysteries, thrillers and other novels, is a former reporter for Honolulu dailies and writer for "Newsweek" magazine. He taught nonfiction writing and journalism at the university level for 10 years. He holds a Ph.D. in American studies.