Ricinus communis

Common names: castor bean

Ricinus communis (castor bean) is an semi-woody large shrub (family Euphorbiaceae). Native to the southeastern Mediterranean, eastern Africa, and India, it has escaped cultivation and established outside of its historic range to become a noxious weed in many mild climates, including in southern and central California. It has a shrubby habit but can reach the height and stature of a tree in mild, seasonably moist growing conditions. Leaves are large, palmately shaped, initially crimson/maturing to dark green, and glossy, with several pointed lobes and serrated edges. Male and female flowers are spatially separated each inflorescence spike; fruits are capsules containing up to three seeds each. Seeds are large, shiny, and relatively long-lived with the appearance and size of a large dog tick. Plants grow very quickly and can outcompete natives, especially in more disturbed environments such as on steep slopes and along arroyos. Castor bean contains ricin, an extremely toxic chemical that can kill an adult who consumes only four to eight seeds and makes it largely unpalatable to wildlife and livestock. This species is also a preferred host for the polyphagous shothole borer. Handling foliage and seeds can cause severe dermatitis.

Cal-IPC Rating: Limited?

Explanation of Cal-IPC ratings

• High – These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically.
• Moderate – These species have substantial and apparent-but generally not severe-ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal, though establishment is generally dependent upon ecological disturbance. Ecological amplitude and distribution may range from limited to widespread.
• Limited – These species are invasive but their ecological impacts are minor on a statewide level or there was not enough information to justify a higher score. Their reproductive biology and other attributes result in low to moderate rates of invasiveness. Ecological amplitude and distribution are generally limited, but these species may be locally persistent and problematic.
• Alert – An Alert is listed on species with High or Moderate impacts that have limited distribution in California, but may have the potential to spread much further.
• Watch – These species have been assessed as posing a high risk of becoming invasive in the future in California.

CDFA Rating: None?

Explanation of CDFA ratings

• A – A pest of known economic or environmental detriment and is either not known to be established in California or it is present in a limited distribution that allows for the possibility of eradication or successful containment.
• B – A pest of known economic or environmental detriment and, if present in California, it is of limited distribution.
• C – A pest of known economic or environmental detriment and, if present in California, it is usually widespread.
• D – An organism known to be of little or no economic or environmental detriment, to have an extremely low likelihood of weediness, or is known to be a parasite or predator.
• Q – An organism or disorder suspected to be of economic or environmental detriment, but whose status is uncertain because of incomplete identification or inadequate information.
• * – An asterisk next to the rating indicates that a plant is included in the CCR Section 4500 list of California State Noxious Weeds.
• -* – This plant is included in the CCR Section 4500 list of California State Noxious Weeds, but is otherwise not rated.

More details

Assessment(s)

Ricinus communis Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.

Weed Management Notes

• Management Notes - Information on management techniques and effectiveness from the University of California Cooperative Extension’s Weed Research & Information Center.

Cal-IPC Newsletter Articles

• Don’t sell a pest: A new partnership to prevent plant invasions through horticulture. Connick, Sarah; Gerel, Mike. Vol 13, Issue 2
• The basal bark method of applying triclopyr herbicide. Neill, Bill; Angeles, Team Arundo. Vol 13, Issue 1
• Which weeds dominate southern California urban riparian systems?. Burkhart, Brad; Kelly, Mike. Vol 13, Issue 1
• Roundup of Arundo projects reveals commitment, strategic weakness. Kelly, Mike. Vol 07, Issue 2
• Results of the CalEPPC questionnaire at Symposium ’98 in Ontario. DiTomaso, Joe. Vol 06, Issue 4
• Legendary stewardship award. Goode, Suzanne. Vol 06, Issue 2
• Killing the beast: A cooperative approach for control of Arundo donax in the Santa Ana River watershed. Stein, Eric D.; Vartanian, Valerie. Vol 05, Issue 3
• Control of exotic plants in an herbaceous understory. Perala, Christine; Hoover, Doris A.; Parra-Szijj, E.A.. Vol 01, Issue 3

Cal-IPC Symposium Presentations

Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.

• Mapping weeds and rare plants to inform management and conservation in the Zaca and Jesusita fires. Calloway, Stephanie; Schneider, Heather; Knapp, Denise (2018)
• The Matilija Dam Ecosystem Restoration Project. Reinoehl, Steven; Zaich, Craig (2010)
• How to develop user-friendly riparian corridor invasive exotic species/habitat restoration master plans: Experiences on the San Diego and Otay Rivers. Burkhart, Brad; Kelly, Mike (2007)
• Partnering to prevent invasions of plants of horticultural origin. Connick, Sarah; Gerel, Mike (2004)
• Exotic plants in the Sonoran desert region, Arizona and Sonora. Devender, Thomas R. Van; Frlger, Richard S.; M., Alberto Burquez (1997)

Other Ricinus communis Information

• CalPhotos - Images of plants taken mostly in California.
• Calflora - Distribution map and records of this species in California.
• CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
• EDDMapS - Distribution of this species in North America.
• Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
• USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.

Additional photos