Quick Facts

Quick facts

• Originally from West Africa, Castor Oil Plant (Ricinus communis L.) is an annual or perennial shrub which can grow to 6 meters tall.
• It has large shiny glossy 7–9 lobed leaves to 60 cm wide.
• It has scattered populations throughout all the mainland states of Australia.
• It grows along watercourses and floodplains, and neglected areas around towns, old fields and roadsides.
• Its seeds are extremely poisonous to humans and livestock.
• Can be controlled by physical removal cultivation and herbicides, with followup required for 4–5 years.

What Does It Look Like?

What is it?

Castor Oil Plant (Ricinus communis) is an annual or short-lived perennial hairless shrub which can grow to 6 m in height. The plant emits an unpleasant aroma when crushed. The stout hollow stems and branches are a dull pale green or red in colour and pith filled to hollow in the middle. The leaves are arranged alternately along the branches on long, stout, hollow leaf-stalks 10 to 30 cm long attached off-centre to the bottom of the leaf. Each leaf blade is 10 to 60 cm across, divided into 7 to 9 pointed triangular segments with toothed edges and conspicuous veins. The leaf blade is glossy and dark reddish-green in colour when young, becoming glossy and green when mature.

Castor Oil Plant produces separate male and female flowers which are on the same plant. The flowers are arranged in erect clusters up to 15 cm long. The flower clusters are at the end of the branchlets (terminal) or in the leaf-stem junction (axillary). Female flowers occur at the top of the spike and male flowers at the bottom. Neither flower has petals. The male flowers have numerous creamy-white stamens and the female flowers have three forked red styles.

The fruits are spherical in shape, 1 to 3 cm in diameter, covered in red or green soft spines and contain usually three seeds. The seeds are smooth, shiny, grey and silvery-white mottled and 1.2 to 1.5 cm long, somewhat flattened, smooth. The seed is scattered over several metres when released explosively from ripe fruits (Wilson 1989; Parsons & Cuthbertson 1992; Land Protection 2006).

For further information and assistance with identification of Castor Oil Plant contact the herbarium in your state or territory.

Flower colour

White, Red

Growth form (weed type/habit)

Tree, Shrub

Where it currently grows? Preferred habitat

Castor Oil Plant is generally abundant along watercourses and floodplains, neglected areas around towns, old fields and roadsides (Wilson 1989; Parsons & Cuthbertson 1992, Land Protection 2006).

Are there similar species?

Castor Oil Plant superficially resembles Bellyache Bush (Jatropha gossypifolia) but that species has stems and leaves covered in sticky hairs, 3 to 5 lobed leaves and smooth fruits that are 1.0 to 1.2 cm in diameter (Wilson 1989; Wheeler 1992).

Why Is It A Weed?

What are its impacts?

Castor oil plant is is poisonous to people and animals.  It also invades pastures, reducing productivity.  It can out compete native plants and reduces habitat and food for native animals.

Agriculture: The plant is unpalatable and is rarely grazed by stock. This can lead to the plant invading pastures especially those on alluvial soils and cause a significant loss of prime grazing land (Wilson 1989; Parsons & Cuthbertson 1992). Castor oil plant is poisonous to dogs and livestock including cattle, horses, pigs, sheep and poultry. Livestock rarely eat this weed due to the odour of the leaves. However, poisoning can occur if grain is contaminated with seeds. Symptoms are similar to human poisoning. It may take a few hours or days for symptoms to appear. Honey bees have been poisoned by castor oil plants (NSW 2019). The seeds of Castor Oil Plant are extremely poisonous to humans and livestock (Wilson 1989; Parsons & Cuthbertson 1992).

Native ecosystems: common also waterways in open areas and wherever there is disturbance. If left untreated, Castor Oil Plant will grow to form dense stands along river banks and can grow to large sizes, outcompeting with native plants. 

Human poisonings: Castor oil plant contains a toxin called ricin. It is toxic to humans, capable of causing serious illness and death. Flowers, leaves and especially the seeds are poisonous. Eating castor oil plant causes, a burning sensation in the throat and mouth, vomiting, abdominal pain, diarrhea and bleeding, bleeding from the eye and mucous membranes, respiratory and cardiac distress and failure. Temporary blindness may occur if the sap gets into the eyes. Touching leaves and seeds can cause dermatitis in people with sensitive skin.

What to do if a person is poisoned:

• If the patient is unconscious, unresponsive or having difficulty breathing dial 000 or get to the emergency section of a hospital immediately.
• If the patient is conscious and responsive call the Poisons Information Centre on 13 11 26 or your doctor.
• If going to a hospital take a piece of the plant for identification.

How does it spread?

Castor Oil Plant is primarily spread by seed that is scattered over several metres when released explosively from ripe capsules. Longer distance dispersal of seeds can be through water movement along streams and movement of soil containing seeds by animals and machinery (Parsons & Cuthbertson 1992).

What is its history in Australia?

Castor Oil Plant was recorded as being present in Australia in 1803. It has become naturalised in all mainland states (Parsons & Cuthbertson 1992).

How To Manage It?

Best practice management

Castor oil plant can be controlled by hand pulling or digging out seedlings and young plants, and slashing, mowing and cultivation, herbicides. Follow up any control work is required to treat plants that have re-grown or stop new plants from growing and seeding, with site checks needed for 4–5 years. Be careful when controlling this plant as it is poisonous. Wear protective clothing including gloves and eye protection before starting control work.

Non-chemical control: Individual plants of Castor Oil Plant can be removed by cultivation, digging or hand pulling (Wilson 1989; Parsons & Cuthbertson 1992; Big Scrub Rainforest Landcare Group 2000). Young plants can be hand pulled or dug out quite easily. Larger plants can be removed if the soil is damp. It is important to remove as much of the roots as possible to stop the plant from re-growing. Large areas of castor oil plant can be slashed or mown, followed by cultivation. Keep cultivation shallow to stop seeds from being buried deeply. Deeper burial can cause dormancy in seeds and this could make control difficult in future. Check the area and control any regrowth or new seedlings (NSW DPI 2019).

Chemical control: Large individual plants can be cut and the stumps immediately painted with an appropriate herbicide (Parsons & Cuthbertson 1992). Larger infestations may require foliar spraying with herbicides (Wilson 1989). Alternatively, application of an appropriate herbicide by soil injection. Castor Oil Plant is susceptible to several herbicides and spraying actively growing plants gives good control (Parsons & Cuthbertson 1992). Cut trunks or stems and apply herbicide within 15 seconds.

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Castor Oil Plant forms a perennial shrub or tree in the tropical and subtropical regions, whereas in temperate regions it is usually an annual. The plants at all stages of growth are very susceptible to frosts. The seeds germinate usually in spring to early summer. Seedlings and juveniles grow rapidly with suitable growing conditions. Flowering can occur throughout the year, but mostly during the summer months especially in the temperate regions (Weber 1986; Wilson 1989; Parsons & Cuthbertson 1992).

Where Is It Found?

Which states and territories is it found?

NSW, NT, QLD, SA, VIC, WA

What areas within states and territories is it found?

In Australia, Castor Oil Plant has scattered populations throughout all the mainland states (Parsons & Cuthbertson 1992). 

In Western Australia it is found mostly along the west coast from Shark Bay south to Bunbury but with scattered records from near Kununurra, Port Hedland, Comet Vale and Esperance (AVH 2021; Western Australian Herbarium 1998 – ). 

In the Northern Territory it is mainly in the Alice Springs and Victoria River regions (Wilson 1989). 

While in South Australia Castor Oil Plant occurs as scattered colonies from the far north west to the south east corner of the State (eflora 2021). 

It also occurs as a casual garden escape in Victoria (Parsons & Cuthbertson 1992). 

It is spread and common along the east coast of Australia from Torres Strait, Queensland south to near Jervis Bay, New South Wales with many scattered populations in inland areas of Queensland and New South Wales (AVH 2021).

Where does it originate?

Castor Oil Plant is native to north east tropical Africa. It has been cultivated throughout the tropics, subtropics and warm temperate regions of the world for the oil from the seeds. It has become widely naturalised in many countries (Smith 1987).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Ricinus communis

Other scientific names (synonyms)?

Does it have other known common name(s)?

Jarak (Christmas Is.), Castor Bean, Castor Oil Bush, Palma-christi, Mamona