Weed Identification

Australia > > Castor Oil Plant

Castor Oil Plant

Ricinus communis

Family: Euphorbiaceae.

Form: Shrub

Origin: Native to Africa and Eurasia.

Flowers/Seedhead: Flowers: In terminal clusters or at the leaf-stem junction (axillary); upper flowers female, reddish; lower flowers male. Flowers late summer in temperate areas or late in rainy season in tropical zones.

Description: Spreading shrub to about 6 m tall. Perennial in moist areas, annual in frosty areas. Roots thick and fibrous. Seed at first in a soft, spiny, green capsule that dries to reddish-brown; each capsule about 2 cm long. Seeds smooth, patterned black and fawn and to 1.7 cm long.

Distinguishing features: Distinguished by large palmately divided leaves, objectionable smell of leaves when crushed and hollow stems. Leaves to about 50 cm diameter when mature, with 79 lobes.

Dispersal: Seeds ejected explosively. Cultivated for castor oil.

Fruit in early stage of development
& leaves

Notes: Introduced to Australia and noted in records in 1803. Now in all States except Tasmania. Widespread and common in wasteland. Seedlings and juveniles grow rapidly. Castor oil is extracted from seeds. Seeds contain the toxin ricin. Toxicity to stock differs with the animal. Humans are sensitive to the toxin and a few seeds ingested may kill. Leaves are unpalatable and unlikely to be eaten by stock. Castor Oil Plant is scattered over the distribution shown on the map.


    Flora of NSW. G. Harden (ed), Vol. 1, 1990, pages 405406. Noxious Weeds of Australia. W. Parsons and E. Cuthbertson, 1992, pages 431433.

Left: flowerhead: female fls upper, male fls lower
Right: seed & spiny capsule

Left: seed leaves (cotyledons)
Right: seedling at 2-leaf stage

This weed has been included in the WEEDeck field guide as card S05

More information about WEEDeck is available from Sainty & Associates Pty. Ltd.


Australia > > Castor Oil Plant


National Weeds Strategy
Telephone: (03) 6344 9657
Fax: (03) 6343 1877
Email: jthorp@weeds.org.au

Privacy Statement

Legal Notice

Site Design - Computer Support Tasmania
Australian Weeds Committee