The name gives it away. Megaherbs are particularly large herbs. 'Carrots', 'cabbages' and giant diasies up to 1.5 meters tall with big, colourful flowerheads and leaves the size of dinner plates. They are only found on a handful of islands south of New Zealand in the middle of the Southern Ocean, in a zone between the temperate and the Antarctic. The sub-Antarctic. Here, extreme temperatures are not the main problem: rather, the near-constant wind, rain and general cloudiness make it challenging for both the plants and their pollinators.