Common Australian Garden Weeds

Ricinus communis

Scientific name: Ricinus communis L.


Castor oil plant (Ricinus communis) with large lobed leaves.


Inflorescence of castor oil plant with mature fruit on the upper left.


Close-up of inflorescence with female flowers on top (with red stigmas) and male flowers below (with yellow stamens).



The immature spiny fruit of castor oil plant.


Young castor oil plants (note the large cotyledons with entire margins).

Common name: Castor oil plant, castor bean, Palma Christi

Family: Euphorbiaceae

Origin:

Native of Asia and Africa.

Habit:

Perennial shrub with large leaves growing up to 4 m tall.

Habitat:

Common weed of creek banks neglected suburban blocks and other waste places.

General description:

Stems and leaves

Stems are pale, dull green with a reddish tinge, hollow and hairless usually growing up to 2 m long. Leaves are large 10-70 cm in diameter with seven to ten triangular lobes. Young leaves are reddish brown. Petioles (leaf stalks) are 10-30 cm long. Leaves are arranged alternatively.

Flowers and fruit

Inflorescences form at branch tips. Flowers are of separate sexes with fluffy cream-coloured male flowers at the base of the inflorescence and female flowers, with conspicuous red stigmas, at the top. Flowering occurs mainly in summer. Fruits are greenish-red, egg-shaped, spiny capsules 1.5-2.5 cm across. Seeds are mottled 1 cm long. Fruits divide into three segments each containing a single seed.

Distinguishing characteristics:

A large robust shrub with large leaves up to 60 cm across with 7-9 triangular lobes. Crushed leaves have a sickening smell. Flowers are borne in erect spikes of reddish, green egg-shaped spiny fruits

Noxious status:

It has been declared as a noxious species in New South Wales and the Northern Territory.

Sources:

Kleinschmidt, H.E., Holland, A. and Simpson, P. (1996). Suburban Weeds. 3rd Edition. Department of Primary Industries, Brisbane.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious Weeds of Australia. Inkata Press, Melbourne.

Stanley, T.E. and Ross, E.M. (1983-1989). Flora of South-eastern Queensland. Volume 1. Department of Primary Industries, Brisbane.

Anonymous. (2000). Noxious Weed List for Australian States and Territories. Prepared by the National Weeds Strategy Executive Committee.

Auld, B.A. and Medd, R.W. (1996). Weeds: An Illustrated Botanical Guide to Weeds of Australia. Inkata Press, Sydney.