Sève bleue, New Caledonia

Through a quirk in geology, New Caledonia’s main island, Grande Terre, holds a fifth of all the world’s known deposits of nickel. If you cut a sève bleue twig, glistening globules of turquoise appear. Sève bleue means ‘blue sap’, and an astonishing 11 per cent of the weight of the sticky sap can be nickel, a concentration far in excess of any other living material. While other plants don’t absorb nickel from the soil in the first place, the sève bleue uses the nickel as a cheap poison to repel insects that would otherwise eat the tree.