Chamaesyce prostrata

prostrate sandmat

Chamaesyce prostrata

(Alton) Small 1903

pronounced: kam-ay-SY-kee pross-TRAH-tuh

(Euphorbiceae — the spurge family)

synonym — Euphorbia prostrata

Alton 1789

pronounced: yoo-FOR-bee-uh pross-TRAH-tuh

common names: prostrate sandmat, red caustic weed

I am placing this plant in the Chamaesyce genus with some misgivings. All of the Australian sources consulted give it as the accepted name, with Euphorbia prostrata as the synonym; but GRIN and Kew place it in Euphorbia. My inclination always is to follow Kew, but this time I yield again to the Australian usage, for consistency’s sake. Chamaesyce is derived from the Greek χαμαι (chamai), on the ground, and συκον (sykon), a fig; prostrata is from the Latin prostratus, thrown to the ground, prostrate.

The caustic weeds are a group of small plants found throughout the tropical and subtropical regions of the world. They are generally small, short-lived, creeping plants, usually less than 10 cm tall and forming a spreading mat on the ground. Some species are slightly larger (up to 40 cm or more) and may be semi-upright. All have a milky sap that exudes from stem and leaves when they are broken. dangerous 2This sap is caustic, and can cause irritation if it comes in contact with the skin or the eyes. All have very inconspicuous flowers borne singly in the leaf axils or in dense clusters near the tips of the stems.

The Prostrate Sandmat has several stems up to about 20 cm long, sparsely hairy, and forming dense mats. The stems are sometimes purple-tinted.

The opposite leaves are oblong to obovate, 3 – 10 mm long, 1 - 5 mm wide, finely toothed towards the apex, and the base asymmetric. Triangular stipules, about 1 mm long, are present. There are sometimes dark spots in the centre of each leaf.

The inflorescence is a cyathium less than 2 mm wide with ovate red glands and inconspicuous white to pink narrow petal-like appendages surrounding the actual flowers. There are 4 male flowers and a single female flower.

The fruit is a lobed capsule, about 1.3 mm long and 1.2 mm in diameter, the angles ciliate. The seeds, about 1 mm long, are 4-angled, pale brown, often with a whitish bloom.

The plant, originally from tropical America, but now widely naturalized in many other parts of the world, is often found in cracks in paths and gardens, and is widely distributed in Queensland, NSW, the Northern Territory, and less widely in Western Australia. It usually generates following rain in spring or early summer. Flowering occurs within weeks of germination and can continue until early autumn, after which the plants usually die. Several generations are often produced in a single growing season. The seeds are spread by mowers, vehicles, animals and floodwaters.

In some countries, especially India, an extract of the plant is used to treat bleeding haemorrhoids, due to its contents of flavonoids, phenolics and phenolic acids.


­­­­­­­­­­­­­­­­­­­­­­ 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 in Nelly Bay 2011
Page last updated 5th November 2018