The plant life on New Zealand's subantarctic islands have been officially recognised by International Union for Conservation of Nature (IUCN) who describe the region as a world centre of floristic diversity.

The islands host around 250 vascular plants, with 35 of these found only in the region and several found only at a single island or group. Except for the Bounties and the Western Chain of The Snares the islands are well vegetated.

Megaherbs

The most well known component of subantarctic flora are the megaherbs – species which have grown to a large size and generally have big, colourful flowers.

The megaherbs exist in 10 taxa endemic to the region and they occur in four genera: the large leaved Pleurophyllum and Stilbocarpa and the colourful Anisotome and Bullbinell. They all contribute hugely to the character of the islands.

Forest

Forest cover is restricted to The Snares and the Auckland Islands. Olearia lyallii, a large tree daisy which reaches a height of over 5m, dominates the forest on The Snares. Olearia is a significant feature of the Auckland Islands too, along with southern rata (Metrosideros umbellata), which is the main species in the coastal forests of the Auckland Islands.

No equivalent forest exists on the Campbell or Antipodes island groups. The tallest species on Campbell is Dracophyllum (grass tree or turpentine scrub) which forms a dwarf forest three to five metres tall.

Campbell is also home to the worlds loneliest tree: a single planted sitka spruce whose closest tree neighbour is on the Auckland Islands.

For both Campbell and the Antipodes island groups, tussock grasslands and herbfields are more extensive than the areas of shrubland.

Bounty Islands plants

While the waters around the Bounty Islands abound in a wide variety of marine algae (seaweeds) the only true terrestrial plant is a few specimens of Lepidium (Cook's scurvy grass).