Caper Spurge (Euphorbia lathyris), another latex-exuding Southern European ornamental selection, now naturalised in riparian woodlands throughout Southern Australia.
Caper Spurge combined excellent vertical structure, drought-hardy toughness, and fantastic seed pods with a capacity to establish and sustain itself as an environmental weed around the fringes of Melbourne. Despite having a limited annual/biennial life pattern, reproductive success and explosive seed release allows the plants to form localised infestations of longer standing, with opportunity for mechanical or hydraulic transport to new sites.
The common name ‘Caper Spurge’ is reflective of a deep confusion. The plant was a source for panic in 19th c. Australia, having been associated by 1877 with ‘several cases of poisoning… through eating the fruits, among children, at Parramatta and other places.’ For posterity, let’s be clear: Capers are the buds of certain of a family of flowering trees in order Brassicales, vaguely related to mustards and kales. Caper Spurge is a Euphorbia, in a different order (the Malpighiales, which translates to ‘malclassified weirdos’), and offers from beneath space-blue stems an irritating exudate which should be evidence enough that the entire plant is a toxic, carcinogenic tire fire.
Although the first digitised herbarium record was collected at Hobart in 1876, newspaper columns imply that it was already a weed in various parts of NSW in the 1870s, with samples sent to Australian Town and Country from Spring Grove (1875), Collaroy (1877) and Lahrip Creek (1878). In 1894, it was recorded on the Hopkins River at Ararat in Victoria, with collectiond at Melbourne in 1895 (‘Port Phillip’) and 1907 (at Coburg and Werribee).
Today, populations are concentrated along major rivers and creeks: the Yarra and the Plenty Rivers, the Maribyrnong River, the Werribee River. The photographed plants form a well-established but recent colony on a constructed rock embankment above Kororoit Creek in Laverton North.