Megaherb

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.

[11] They live in the wet, windy and cold environments of the subantarctic islands, where they coexist with cushion plants and tussock grasses but trees are absent.

A single species, Pleurophyllum hookeri, covers almost a third of Macquarie Island[12] where another megaherb, Stilbocarpa polaris, also occurs.

[17] The most extraordinary of the megaherbs is the Pleurophyllum meadow, a community dominated by the large-leafed herbaceous composite, producing a floral display second to none outside the tropicsThey are the best known plants of the New Zealand subantarctic islands[18] and are important components of the biodiversity of the region.

[7] Note megaherb species are the Campbell Island carrot (Anisotome latifolia) and the Ross lily (Bulbinella rossii).

[27] The species Aciphylla latifolia, Bulbinella rossii, Myosotidium hortensia, Pleurophyllum spp.

[31] The leaves may also act to absorb heat from diffuse radiation[17] and higher temperatures have been measured in megaherbs than the surrounding environment.

[32] At the same time, the lack of herbivores, plentiful water and nutrients brought by e.g seabirds and steady temperatures facilitate the growth of large plants.

[7] Herbs with large leaves occur in other places such as Chile, Hawaii, Kenya and New Zealand but there are traits specific for subantarctic megaherbs[37][30] and there are environmental differences, such as lower and more steady insolation.

[1] Megaherbs draw the interest of scientists and tourists alike;[16] they are the main claim to fame of Campbell Island for example.

[33] The characteristic appearance makes Pleurophyllum a plant that could be used in horticulture, but attempts to cultivate it outside of the subantarctic environment have largely been unsuccessful.

[43] On Macquarie Island, rabbits consume megaherbs while rats cache seeds of Pleurophyllum hookeri[44] in places unsuited for their germination,[45] and the growth of the rabbit population has resulted in a major reduction of megaherb populations, as well as of other plant taxa of the island.