Castor Oil plant

Ricinus communis L.

Family: - Euphorbiaceae.


Ricinus is from the name of the European sheep tick Oxades ricinus or sheep tick because the seed looks like an engorged sheep tick.

Communis is Latin for common and used because it is only species in the genus.

Castor Oil plant because castor oil is extracted from the seeds and was used as a replacement for castor produced by Beavers (Castor fiber).

Other names:

Castor bean.


A many branched annual to perennial shrub or small tree to 4 metres tall with stalked, large leaves with 5-9 finger like lobes and softly spiny capsules. It has yellow male flowers below the reddish female flowers from spring to autumn.





Alternate or spirally arranged and widely spaced on branches. Unpleasant odour when crushed.

Stipules - None.

Petiole - Long, 100-600 mm long with large nectary. Attached to the lower leaf surface away from the edge Hairless.

Blade - 150-300 mm long by 100-600 mm wide, circular to broadly egg shaped in outline with 5-9 fingers, shiny red-purple when young becoming shiny green with age. Fingers are elliptical, pointed at the tip and have a serrated edge and obvious veins. Hairless.


Up to 4000 mm tall, branched, hollow, stout, woody, dull pale green and often tinged with red. Soft wood. Hairless.

Flower head:

Loose, erect, stout spike like raceme in the axils of upper branches, often 150 mm or more long, on a thick stalk (peduncle) with flowers on short stalks (pedicels). Many large, spiny capsules are clustered together when ripe.


15-20 mm diameter. Yellow male flowers are lower than the reddish female flowers on the same raceme.

Ovary - 3 celled. 1 ovule in each cell. 3, forked, red styles fringed with warts.

Sepals - 5, membranous, egg shaped segments, 6-8 mm long, pointed tips, joined near the base, persistent in the male flower but fall off in the female flower. Hairless.

Petals - None.

Male flowers.

Stamens - Many. Filaments repeatedly branched.

Anthers - 2 globular cells. Open by lengthwise slits.


Egg shaped to triangular pyramid or 3 lobed, red-green capsule with soft conical and curved spines, woody, 15-20 mm long by 15 mm wide with 3 seeds. Fruit explodes when ripe dispersing the seeds several metres.


Large, 9-17 mm long by 6-10 mm wide, slightly flattened, smooth, black or grey and white, mottled with a fleshy appendage at one end. Looks like and engorged tick. Oil extracted from seeds or 'castor beans'.


Many thick and fibrous laterals.

Key Characters:

Large shrub.

Large palmate leaves.

Spiny seed capsules with mottled seeds.


Life cycle:

Annual biennial or perennial. Germinates from autumn to spring and grow quickly. They may reach a height of several metres in their first year. Flowers from August-March depending on the area. Seed may be set in the first year. Growth slows or the plants die in winter. Surviving plants commence rapid growth in spring. It behaves as an annual in frosty areas.


Sensitive to frosts.

Drought tolerant.

Very rapid growth rates.


By seed.

Flowering times:

Summer to autumn in western NSW.

December to March in SA.

Mainly August to September in Perth.

Seed Biology and Germination:

Seed may emerge from 300 mm deep in the soil.

Seed has medium longevity.

Vegetative Propagules:

Stems may coppice when damaged.



Population Dynamics and Dispersal:

Spread locally several metres by the explosive release of seed from the ripening capsule. Mammals, water flows, road making and mud on vehicles also contribute to spread.

Long distance spread is usually from intentional planting or dumping of garden refuse.

More abundant after heavy rains or floods.

Origin and History:

Tropical Africa and Asia.

Introduce to Australia before 1803.





Mediterranean. Sub tropical. Warm temperate.



Plant Associations:



Castor oil extracted from the seeds for a lubricant and hydraulic fluids because its viscosity is stable as temperature increases.

Used in paints, varnishes, plastics, nylon, rayon, urethane, explosives, textiles finishes and perfumes.

Used medicinally as a purgative.


Grown for oil production overseas.

Used by Egyptians for embalming bodies.


Weed of gardens, streams, sandy lake margins, wetlands, pastures, roadsides, railways, refuse sites and disturbed areas.



Seeds contain ricin and are poisonous to stock and poultry and humans, but they are not usually eaten voluntarily.

Ricin is very toxic with a minimum lethal dose by injection of 0.0001 mg/kg body weight.

Seeds are very toxic to humans and 6-8 seeds may cause death.

Seeds produce an allergic reaction in skin.

Causes gastrointestinal irritation.

Stock deaths reported after

1) eating contaminated cereal grains,

2) residues after oil has been extracted and

3) drenching with industrial castor oil.

4) being fed on leaves.

Powdered plants are an irritant causing lip swelling, conjunctivitis, and bronchial congestion.

Leaves are also toxic but probably due to a different substance than the ricin found in the seeds.

Cases of poisoning in the field are rare. Cattle sometimes eat young leaves and stems without ill effects. Fresh and dried leaves are equally toxic.

Horses are most sensitive followed by sheep, cattle and pigs and poultry are the least sensitive.

Seeds and oil can be made safe by heating to 500C or more.


In people, a burning sensation in mouth and throat and abdominal pain occurs almost immediately and dermatitis may follow.

In animals symptoms take hours to days to develop.

Loss of appetite, incoordination, abdominal pain, diarrhoea, increased temperature, convulsions, weakness, blood stained faeces, trembling, sweating, fast and weak pulse, or massive body wrenching heart contractions, dullness, cessation of cud chewing in ruminants and vomiting in pigs, coma and death.

In poultry, depression, ruffled feathers, drooping wings, grey wattles and combs.

Seeds tend to cause gastro intestinal symptoms above and leaves cause neuro-muscular symptoms.


Remove animals from infestation.

Small quantities of the plant may immunise animals against toxicity.

Don't chew castor oil seeds as a laxative.


Noxious weed of NSW.

Management and Control:

Slashing followed by shallow cultivation usually gives reasonable control. Repeat cultivations are normally required to control late germinating seedlings.


Eradication strategies:

Manually remove or cultivate small infestations. Larger infestations are usually treated with herbicides. Glyphosate and Tordon 75-D usually give good control.

Herbicide resistance:

Biological Control:

Related plants:


Plants of similar appearance:

Bellyache Bush (Jatropha gossypifolia)


Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P162. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P514. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P465. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P284.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P124.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P146-147. Photo.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1061.1.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P455.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P115. Diagrams.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P431-433. Photos.


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