Castor Oil Plant Ricinus communis

Castor Bean is an exotic ornamental, semi-woody, fast-growing, large shrub or small tree that is extremely toxic to humans. It can be fatal if only a few seeds are ingested and also causes contact dermatitis when the foliage is handled. It is an herbaceous perennial in winter hardy zones 9 to 11. In colder climates, it is a warm weather annual that readily reseeds itself. The Castor Bean has large, palmately lobed leaves, spiking yellowish-greenish flowers, and spiny seed capsules. It is a member of the  Euphorbiaceae or spurge family.

This plant is native to tropical east Africa, but it has naturalized and weedy in many tropical and subtropical areas around the world including the United States. It is usually found along riverbeds, railroads, roadsides, fields, pastures, or other disturbed areas. Castor bean is a noxious weed in southern and central California. The plant is classified as Category II invasive species in the State of Florida.

The genus name, Ricinus, is the Latin word for "tick." This name was given since the seeds resemble a species of European tick. The epithet, communis, means common.

Plant in full sun in rich moist soils.  Fertilize regularly for the best growth.  Pruning may be necessary to shape the plant. Plants will have low drought tolerance until well established. This shrub is not wind resistant and is easily blown over. Staking may be required. It produces a large number of seeds and readily reseeds itself.

Every part of the plant is poisonous if ingested. The castor bean contains a highly poisonous substance known as ricin that when inhaled or ingested can be lethal to humans and animals. As a preventative measure, the seed capsules may be pinched off when they are small to remove the poisonous seeds from the plant. Handling the foliage may cause severe contact dermatitis Wear gloves and other protective equipment to avoid allergic skin reactions.

Do not plant this in areas where children or pets play due to its toxicity.  In the appropriate area, the beautiful and bold foliage adds color and texture to the landscape. Consider this plant as a specimen, container plant, or informal hedge. It is important to remember that this plant grows very fast, and seeds germinate regularly. Plant with purpose and maintain the area to prevent invasiveness. Perhaps better yet, consider a native alternative such as the American Beautyberry, Yaupon Holly, or Fragrant Sumac.

Seasons of Interest:

Bloom: Summer and Fall   Foliage:  Spring, Summer, and Fall   Fruits:  Fall

Quick ID Hints:

• annual or herbaceous perennial shrub or small tree, usually up to 6 to 10 feet tall and 2 to 4 feet wide
• stems are red to green or purple
• leaves are glossy, green, star-shaped with 5 to 11 points, serrated margins, and measure 6 to 30 inches wide
• non-petaled yellowish-green flowers appear on spikes measuring up to 18 inches long on the top of the stem
• fruit capsule is red, green, or purple, round, covered in dense spines
• seeds are mottled, smooth, and resemble an engorged dog tick

Insects, Diseases, and Other Plant Problems:  The castor bean has no serious insects or disease problems. Spider mites occasionally attack drought-stressed plants.

VIDEO created by Andy Pulte for “Landscape Plant Identification, Taxonomy, and Morphology” a plant identification course offered by the Department of Plant Sciences, University of Tennessee.