Castor oil plant

• Flowering shrub generally up to 3m tall and occasionally taller.
• Younger branches are stout, hollow, dull pale-green or red.
• Trunk and older branches turn greyish.
• Leaves are glossy dark reddish-green when young, glossy green when mature, 15-30cm across, sometimes up to 60cm, widely spaced on branches, with hollow stems.
• Flowers are reddish-green, crowded in stout, erect spikes in forks of upper branches.
• Fruits are 2.5cm across, covered with soft green or red spines, with 3 segments.
• Seeds are 1 per segment, mottled, smooth, 1.2-1.5cm long, 6-10mm wide.

• Prefers warm and subtropical regions.
• Abundant along gullies, watercourses, floodplains and roadsides, and on disturbed land or wasteland.
• May be common locally after heavy rains or floods.

• Found throughout Queensland.

• Seeds germinate in spring.
• Flowering occurs December-March.
• Can grow up to 6m tall within 12 months.

Economic

• Spreads over sandy soil areas, creekbanks and gullies, leading to significant loss of prime grazing land.

Social

• Seeds contain ricin, which is toxic to humans and livestock.
• If eaten, leaves tend to cause neuro-muscular disorders.

• When ripe, fruits explode and throw seeds several metres.
• Also spread by roadside slashing, vehicles, animals, garden waste.

• Find out how farmers can prevent weed spread.
• Find out how gardeners and outdoor enthusiasts can prevent weed spread.

Physical control

• Remove individual plants by cultivation or hand-pulling.

Herbicide control

• Herbicides are effective.

See the Castor oil plant fact sheet (PDF, 1.7MB) for herbicide control and application rates.

• Castor oil plant is not a prohibited or restricted invasive plant under the Biosecurity Act 2014. However, by law, everyone has a general biosecurity obligation (GBO) to take reasonable and practical steps to minimise the risks associated with invasive plants under their control.
• Local governments must have a biosecurity plan that covers invasive plants in their area. This plan may include actions to be taken on Castor oil plant. Some of these actions may be required under local laws. Contact your local government for more information.