The castor oil plant is a perennial spurge from the tropics and subtropics that can grow up to twelve meters high within a few years. In Europe north of the Alps, it thrives only as an annual and reaches a height of two meters. Here it is planted in gardens because of its decorative, palmately divided leaves, which grow to about half a meter.

The castor oil plant has been cultivated for thousands of years and it is no longer possible to determine whether its original distribution area was in India or Ethiopia. In the Mediterranean region it has gone wild and grows on roadsides and rubble sites. Its spiny capsule fruits contain three oily, red-braun marbled seeds that contain castor oil. On plantations, the castor oil plant lives up to its name: the first harvest is achieved after just a few months. The main exporters of castor oil are India, Brazil and China.

The seeds of the castor oil plant consist of 40 to 50 percent castor oil. Cold-pressed castor oil is colorless to slightly yellowish, very viscous and, thanks to its exceptionally high density, almost as heavy as water. It consists of at least 85 percent ricinoleic acid, which is responsible for castor oil's strong laxative effect. The seeds also contain the protein ricin, which is the most toxic biogenic substance after botulism and tetanus toxin. Since ricin does not dissolve in fat, the toxin remains in the press residue; it is not found in castor oil.