Caustic Weed

Chamaesyce drummondii (Boiss.) Hassall

Synonyms - Euphorbia drummondii

Family: - Euphorbiaceae



Drummondii commemorates James Drummond (1784-1863), an avid collector of plants in Western Australia.

Other Names:


Caustic Creeper

Creeping Caustic

Flat Spurge

Mat Spurge




A small, hairless, low lying annual or short lived perennial herb to 30 cm diameter with corrosive milky sap, usually red stems and blue green, opposite leaves.



Two. Oval. Tip round. Edges smooth. Base tapered. Surface dull blue green. Hairless. Petiole slightly shorter than blade.

First leaves:

Blue green, opposite, oval. Tip flat to indented. Edges smooth to slightly toothed and reddish. Hairless.



Stipules - Membranous, thread like and hairless or very small.

Petiole - Short to almost none.

Blade - Oval. 3-10 mm long by 1.5-6 mm wide. Blue green with a reddish tinge or reddish edges. Tip flat to slightly indented. Edges smooth or with tiny teeth near the tip and often reddish. Base squarish. Surface hairless.


Blue green with a reddish tinge. Low lying, up to 150 mm long. Branched from the base and along their length. Exude a milky sap when broken. Hairless.

Flower stem -

Flower head:

Flower head small, 1 mm long, single or clustered on a short stalk arising from the leaf axils with flowers on a short stalk and enclosed in a calyx like structure (cyathium) which has tiny hairs on the lobes. One female and several male flowers in each group.

Fringed with red glands with a pink or white appendage. Glands almost obsolete or narrow and almost smooth edged or broad and irregularly tooted.


Tiny. Male and female flowers. Male flowers consist of a single stamen. Single female flower is later extruded on a curved stalk (pedicel).

Ovary - Superior

Style notched or with 2 arms.

Calyx - like structure surround the flowers.

Stamens - 1

Anthers - 1. Cells distinct and globular


Globular, pale green capsule, small, 1.5-3 mm diameter with 3 lengthwise grooves. 3 celled with 1 seed in each cell. Tip indented. Edges rounded. Base with stalk remnant. Surface dimpled. Hairless.


Whitish grey to red brown, angular, somewhat triangular, 1-1.5 mm long by 0.5 mm wide. Tip rounded. Edges smooth. Base flattish. Surface minutely roughened.



Key Characters:

Small prostrate plant


Exudes milky latex when damaged.

Leaves almost always opposite, inequilateral at base. ovate to oblong, 3-9 mm long by 1.5-6 mm wide.

Stipules small and membranous and usually present.

Stems commonly red

Flower heads apparently solitary in the axil of the pair of leaves (really an aborted cyme)

Perianth replaced by a calyx like involucre containing 1 female and several male flowers.

Male flowers consist of a single stamen.

Glands of involucre usually red with toothed or entire borders.

Seeds without caruncle (a fleshy appendage near the funicle)

Adapted from John Black, Nancy Burbidge and Judy Wheeler.


Life cycle:

Annual or biennial or short lived perennial running herb. Seeds germinate at any time with a flush in spring to summer. Plant grows quickly over summer.


Drought tolerant once established. It becomes very red under stress.

Caustic, corrosive, milky sap.


By seed.

Flowering times:

Most of the year in SA.

Spring to early summer in Western NSW.

Usually form July to September and March to May in the Perth Region

Seed Biology and Germination:

Vegetative Propagules:



Population Dynamics and Dispersal:

Usually grows as isolated plants but may form small, dense colonies.

Origin and History:

Native to Australia, including tropical and desert WA.





Temperate to sub tropical.


Occurs on a wide range of soil types.

Prefers fallows or bare areas.

Plant Associations:

Wide range



Fodder but not usually eaten in great quantity if other feed is available.

Medicinal used by Aborigines for snake bite and genital disease. Bushmen used the milky sap as an aid to healing. Also used for dysentery and low fever.


Weed of crops, fallows, pastures, gardens and paths.

Colonises bare areas quickly.


Sap can burn eyes and skin.

Toxic to livestock including sheep, horse and cattle. Most deaths occur when there is little other green feed or hungry stock are introduced to dense infestations. When consumed as part of a mixed diet it appears to have little effect on animals.



Remove stock from infested areas. Don't introduce unaccustomed stock to dense infestations.



Management and Control:

Maintain a good cover of vegetation.


Eradication strategies:

Small areas may be treated with a mixture of 20 mL diuron(500g/L) plus 0.5 g chlorsulfuron(750g/kg) plus 25 mL wetting agent in 10 L water. Spray the plants and a 4 metre buffer area until just wet. Repeat when new seedlings reach the 4-6 leaf stage.

Herbicide resistance:

None reported.

Biological Control:

Unlikely because it is an Australian native plant.

Related plants:

Asthma Plant (Chamaesyce hirta)

Red Caustic Creeper (Chamaesyce supina)

Chamaesyce australis is a poison plant and very similar but is covered with soft hairs.

Chamaesyce dallachyana is very similar but has a fringe of hairs around the fruit.

Chamaesyce nutans

Chamaesyce prostrata is a poison plant


Mexican Fire Plant (Euphorbia heterophylla)

Poinsettia (Euphorbia pulcherrima)

Snow On The Mountain (Euphorbia marginata)

The Crown Of Thorns (Euphorbia splendens)


Tapioca (Manihot dulcis, Manihot esculenta)

Rubber (Hevia guianensis, Hevia brasiliensis)

Plants of similar appearance:

Euphorbia species

Pigweed (Portulaca oleracea) doesn't have milky sap and has yellow flowers.


Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P160. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P508. Diagram.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P245.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P456.

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

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P. Diagram.

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). P142.

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

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #235.2.

Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P449.

Moerkerk, M.R. and Barnett, A.G. (1998). More Crop Weeds. R.G. and F.J. Richardson, Melbourne. P79. Diagrams. Photos.


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