Ricinus communis

castor oil plant


Ricinus communis

L. 1753

pronounced: RISS-ih-nuss KOM-yoo-niss

(Euphorbiaceae — the spurge family)


common name: castor oil plant

Ricinus is so named because its seeds resemble a Mediterranean sheep tick of the same name; communis is Latin for ‘common, ordinary’.

A native of Africa and Eurasia, the Castor Oil Plant is a tall, spreading shrub up to 3 m in height, sometimes higher, often found in disturbed areas and landfill sites. It was introduced into Australia in the very early days of European settlement, certainly by 1803. It is perennial in moist areas, annual in frosty areas. The roots are thick and fibrous.

The leaf blade is divided into 7 to 9 serrate lobes, each with a prominent midrib radiating from the point of attachment of the leaf stalk. These leaves produce a nauseating odour when crushed.

The flowers are reddish green, appearing in summer. They are about 1 cm in diameter, and occur on stout, erect spikes.

The seed first appears in a softly spined green capsule that dries reddish brown, 1 – 3 cm in diameter, and slightly 3-lobed. Each lobe contains one shiny grey mottled seed. Propagation occurs after the explosion of the seed pods, when the seed is carried by animals, wind and water. Seedlings grow rapidly, and out-compete native species. On Magnetic Island, the plants are most commonly seen growing in dried-out stream beds in the winter.

dangerous 2The seeds of the Castor Oil Plant, and especially the seed coat, are highly toxic, and temporary blindness may occur of the sap of the plant reaches the eyes. Handling of this plant should be avoided. It is a declared noxious weed class 4 throughout NSW, although not declared in Queensland.

According to the 2007 edition of The Guinness Book of World Records, this plant is the most poisonous in the world. Castor Oil seeds have been found in Egyptian tombs dating back to 4000 BC. The slow-burning oil was used by the Egyptians as a fuel in lamps. Herodotus and other early Greek travellers also noted its use in body ointments, and for improving hair growth and texture. Cleopatra is reported to have used it to brighten the whites of her eyes. In the Ebers Papyrus, believed to date from 1552 BC, the oil is described as a laxative.

When I was a boy in the 1930s, Castor Oil was still commonly used as a laxative. That’s progress for you! It was a very fierce one, and dreaded both for its revolting taste and for the violent laxative effect. It was also used by my mother as a threat in the case of bad behaviour! I don’t remember the threat ever being put into effect, but it was certainly a powerful deterrent. Apart from the threat, it was used as a purgative to treat severe constipation. Anyone who has ever had Castor Oil administered will not be surprised to learn that it was used as an instrument of coercion by Mussolini’s Blackshirts in Italy. Dissidents were forced to ingest the oil in large amounts, and this triggered severe diarrhoea and dehydration, which could ultimately cause death.

Global castor oil seed production is currently around a million tonnes per annum. India produces about 60% of this, most of the remainder coming from China and Brazil.

Several cultivars of the plant have been developed as ornamentals.

The Castor Oil plant is a host plant of several Lepidoptera, including:

      • the Castor Semi-Looper Moth Achaea janata;
      • the Yellow Peach Moth Conogethes punctiferalis;
      • the Ailanthus Silkmoth Samia cynthia;
      • the Sinister Moth Pholodes sinistraria; and
      • the moth Berta chrysolineata.


Information about medicinal qualities of plants, or about their use as medicines, is for interest only, and is not intended to be used as a guide for the treatment of medical conditions.


Photographs taken at Butler's Creek, Picnic Bay, & Gustav Creek, Nelly Bay, 2008, 2010
Page last updated 24th March 2019