Caper Spurge

Euphorbia lathyrus L.

Synonyms - Tithymalus lathyrus

Family: - Euphorbiaceae.


Euphorbia honours the Greek physician Euphorbus who discovered the medicinal uses of the spurges.

Lathyrus is from the Greek lathyros, which is an ancient name for a legume, probably Chickling Vetch that has similar strap like leaves.

Caper Spurge because the fruit looks similar to the true Caper (Capparis spinosa). Spurge is from the Latin ex and purgare meaning to purge out and refers to the purgative properties of these plants.


A hairless, branched annual or biennial plant that exudes white, acrid, sap prolifically whenever damaged, with strap like lower leaves to 12 cm long. The large, spongy, nodding fruit have 3 wrinkled seeds in summer.



Two. Sessile, and elongated, about 30 mm long by 3 mm wide. The seedling is erect with a distinct hypocotyl and epicotyl and is hairless.

First leaves:

About 50 mm long by 4 mm wide, hairless, with a pale streak up the centre and a prominent mid-rib on the underside.


The lower stem leaves are paired, at right angles to the pair below, elongated and bent downwards

Stipules - None.

Petiole - None.

Blade - Upper surface dark grey green, lower surface pale green, oblong to lance shaped, 20-150 mm long by 5-30 mm wide, with a distinct pale centre stripe. Edges are often rolled. Tip is a small point. Base indented to squarish or clasping the stem with ear shaped lobes. The midrib is prominent on the lower surface.

Stem leaves - The upper stem leaves may be twice as long as the lower leaves, flat, obtuse tipped, parallel sided or slightly wider at the base, and arise where the stems branch and along the upper stems. Where the stem branches there is one leaf per stem, otherwise they are paired.


Bluish green, normally unbranched initially. When the plant reaches a height of 300-1000 mm, depending on growing conditions, the stem divides into two or four, rarely three or five, branches. These branches themselves sub-divide several times. The stems are hairless with a waxy bloom and up to 1500 mm tall by 5-12 mm diameter when mature.

Flower head:

Cup shaped, 4 mm long with 2 floral bracts underneath. Umbel of 2-6 rays that is 2 forked several times, with large, 20-60 mm long, narrowly egg shaped to narrowly triangular, indented base, floral bracts.

Cups surrounded by a several glands that are crescent shaped, with short blunt horns.


White, 3 mm long, hairless. Has several single stamen male flowers and a female flower of a single pistil. Involucre lobes with tiny hairs.

Perianth - none.

Stamens - Single.

Anthers - Cells distinct, globular.


Globular, 3 angled, pod like, capsule, 10-20 mm in diameter, deeply wrinkled, 3-lobed, 3 seeded.


Brown with darker spots, oblong egg shaped, large, 4-5 mm long by 4 mm wide, wrinkled, network patterned, with a fleshy appendage that looks like a yellow 'hat' at one end of the seed.


Fleshy taproot with fibrous laterals.

Key Characters:

Opposite large leaves. Flower head looks single in the axil of a pair of leaves. Erect or ascending. Hairless. Flower branches an umbel of 2-5 rays. Large wrinkled seeds.


Life cycle:

Annual or biennial. Germination occurs mainly in spring and early summer, with some in autumn. Autumn germinating seedlings go dormant over winter. Growth is rapid over spring. Flowering starts in summer and continues for several weeks into autumn. Both late flowers and early mature fruit will be found at the same time. The mature plant dies off in late autumn or early winter.



By seed.

Flowering times:

November to February in SA.

Summer in WA.

Seed Biology and Germination:

Vegetative Propagules:




Population Dynamics and Dispersal:

When ripe the fruits burst open explosively and the seed is thrown several metres. Long range dispersal is known to occur by seed being carried in rivers. Other means of dispersal are not known.

Sensitive to weed competition.

Origin and History:

Southern Europe and western Asia.

First Australian record was in NSW in 1892.



An occasional weed in most parts of Tasmania. It appears to be more common in the north and north-west.





Most abundant on light soils.

Plant Associations:

Often in colonies in the shade of trees near old settlements or water.




The plant is currently being investigated as a hydrocarbon fuel source.


Weed of roadsides and disturbed areas and along or adjacent to rivers and creeks.


The fruit is toxic.

The white latex-like sap is toxic and caustic and potentially dangerous if accidentally introduced into the eye. It irritates and often blisters the skin.

Stock losses are rare because it is normally unpalatable but it has been suspected of poisoning sheep and cattle in NSW.

Non fatal poisoning of women who ate pickles made from the fruit that was mistaken for capers has been reported.


Noxious weed of TAS.

Management and Control:

Cultivation provides effective control.

In areas that can't be cultivated triazine herbicides provide control.

It usually disappears from competitive pastures.


Eradication strategies:

Herbicide resistance:

Biological Control:

Related plants:

Asthma plant (E. hirta)

Bottle tree Caustic (E. stevenii)

Caustic weed (E. drummondii)

Climbing Caustic (E. sarcostemmoides)

Cypress Spurge (E. cyparissias)

Desert Spurge (E. tannensis ssp. eremophila)

Dwarf Poinsettia (E. cyathophora)

Dwarf Spurge (E. exigua)

Eyebane (E. maculata)

False Caper (E. terracina) is similar but smaller.

Garden weed (E. segetalis)

Gascoyne Spurge (E. boophthona)

Hairy Caustic Weed (E. australis)

Mexican Fire plant (E. heterophylla)

Naked Lady (E. tirucalli)

Petty Spurge (E. peplus)

Plains Spurge (E. planiticola)

Poinsettia (E. pulcherrima)

Red Caustic creeper (E. prostrata)

Red Caustic Creeper (E. thymifolia)

Sea Spurge (E. paralias)

Sickle leaved Spurge (E. falcata)

Snow on the Mountain (E. marginata)

Sun Spurge (E. helioscopia)

Tree Spurge (E. dendroides)

E. dentata

E. hyssopifolia

Plants of similar appearance:

Spiny Caper Bush (Capparis spinosa) is similar and yields the cooking caper, which should not be confused with the toxic fruit of Caper Spurge.


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

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P246.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P270.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P130.

Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P90-91. 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). P144.

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). #535.15.

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). P449.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P422-424. Photos.


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