Euphorbia horrida

Euphorbia horrida, the African milk barrel, or horrid spurge, is a species of flowering plant in the family Euphorbiaceae, native to South Africa. It is a cactus-like shrub showing remarkable similarities to the true cacti of the New World, and thus an example of convergent evolution.^[2] Growing to 1.5 m (4 ft 11 in), it has blue-green, heavily ridged spiny stems carrying solitary green flowers in summer. In temperate regions it must be grown in heated conditions under glass, or as a houseplant on a sunny windowsill.^[3]

Euphorbia horrida is found in arid deserts in the southeastern cape of Africa.^[4] It is found in sandy, gravely soils that remain dry for most of the year. When it does rain, Euphorbia horrida rapidly absorbs water, expanding the ribs and swelling into a rotund, cylindrical shape. ^[5]

When damaged, Euphorbia horrida rapidly releases a white sap, like of most plants in the Euphorbia genus. The sap is toxic, and causes eye and skin irritation. Left to dry, the sap becomes a sticky, clear, and hard-to-remove resin that remains toxic. ^[6]