What is "megaherb"

Megaherbs are a group of herbaceous perennial wildflowers growing in the New Zealand subantarctic islands. They are characterised by their great size, with huge leaves and very large and often unusually coloured flowers, which have evolved as an adaptation to the harsh weather conditions on the islands. Livestock introduced to the islands in the 19th century severely reduced the megaherb population, to such an extent that by the late 20th century the megaherbs were threatened with extinction. Since the removal of the livestock in 1993, the megaherbs have regenerated successfully and dramatically.