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.

Megaherbs occur on many of the subantarctic islands of New Zealand, predominantly on the Snares island group, the Auckland Islands and the Campbell Island group. The plants evolved in response to the climatological and soil conditions and the lack of herbivores on the islands. The weather is largely wet, cold and extremely windy; the soil peaty, acidic and impoverished. The almost continual cloud cover means that the islands experience low light levels.

The term 'megaherb' was first used by James Clark Ross during his 1839–43 Antarctic expedition.Joseph Dalton Hooker, the expedition's botanist, wrote in the Flora of Lord Auckland and Campbell's Islands that the megaherbs produced "a floral display second to none outside the tropics". Although small in size when compared to plants found in the tropics, megaherbs are notable because their size is far greater than other herbaceous perennials found growing in the subantarctic islands: generally the harsh weather and soil conditions experienced there have a stunting effect on plants.

Most subantarctic megaherbs flower en masse in a cycle of approximately three years; in "off" years a few plants will flower but with nowhere near the effect created by the mass flowering.

A major component of megaherb communities is Bulbinella rossii (Ross Lily). This clump-forming plant has strap-like and succulent leaves, growing to 60 centimetres (24 in). The bright yellow flowering spikes are carried on stems up to 90 centimetres (35 in) high. Its nearest relatives appear to be Bulbinella hookeri (Maori Lily) from the New Zealand mainland, and Bulbinella floribunda (Yellow Cat-tail) from South Africa.

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