CAUSTIC WEED

(Chamaesyce or Euphorbia drummondii)

(Photos: E. Cousins; growth habit, close up of leaf, tap root)

We recently found caustic weed on our lower site at Cape Jervis. If you have found it in your garden, you will know it is a persistent little sucker. It is an annual or short-lived perennial herb with a deep taproot. Smooth, thin red stems fan out from the centre and hug the ground; these stems can grow up to 20cm long, and can exude a corrosive, milky sap when damaged.  The oval-shaped leaves are blue-green with a reddish-purple blotch. They grow in pairs with very short stalks, opposite each other along the stems. The tiny flowers have no petals; they grow in small groups that are composed of one female flower surrounded by several male flowers; even so, the entire flower head is fairly inconspicuous. Seeds can germinate at any time, with the biggest flush in spring; then the plants grow quickly over summer.