Family: Euphorbiaceae

Origin, Description & Uses
Ricinus communis (castorbean) is native to northeastern tropical Africa and has since spread widely throughout tropical and subtropical regions of the world. It is a fast-growing shrub to small tree that can reach several meters in height, with large, deeply lobed, glossy leaves that are often reddish or purplish when young. The plant produces distinctive spiny seed capsules containing mottled seeds. Castorbean has been cultivated for centuries for its oil-rich seeds, which are used to produce castor oil for industrial purposes such as lubricants, biodiesel, and some traditional medicinal applications. It is also sometimes planted as an ornamental for its bold foliage.

Risks & Threats
In Hawaiʻi, castorbean is naturalized on all main islands as well as several outlying locations, including Niʻihau (including Lehua), Midway Atoll (Kuaihelani), Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi Island. It was naturalized prior to 1819 and is now commonly found in low-elevation, dry, and disturbed habitats from 0–500 m. This species is naturalized, possesses traits that are cause for concern, and could detrimentally impact tropical island ecosystems. It spreads readily by seed and can establish in degraded areas, roadsides, and lava fields, where it may compete with and displace native vegetation. All parts of the plant are highly toxic to humans and livestock due to the presence of ricin, creating additional risks for people, pets, and wildlife in areas where it becomes established.

High Risk Traits:

• Broad climate suitability (temperate to tropical)
  
• Naturalized and invasive beyond native range
  
• Forms dense, shading thickets (environmental weed)
  
• Unpalatable to grazing animals
  
• Toxic to animals and humans (seeds highly poisonous)
  
• Self-compatible, wind-pollinated
  
• Short generation time (flowers in 40–70 days)
  
• Prolific seed production (up to 150,000 seeds/plant)
  
• Persistent seed bank (up to 30 years)
  
• Resprouts after cutting or fire
  
• Dispersed by water, animals, humans, and contaminated soil/equipment
  
• Tolerates a wide range of well-drained soils

Low Risk Traits:

• No spines, thorns, or burrs
  
• No fire hazard
  
• Not shade tolerant
  
• No vegetative reproduction
  
• Not wind-dispersed
  
• Well controlled by herbicides