On the western side of the divide, temperate rain forest reaches from the sea to a height of 4,000 ft, and in some places glaciers extend well below the bush line, e.g., Fox and Franz Josef Glaciers. The forest is composed of beech (Nothofagus menziesii and N. fusca) with rata (Metrosideros lucida), and rimu (Dacrydium cupressinum) at lower elevation. This is succeeded by a belt of subalpine scrub and finally by snow grass up to the vegetation limit which is permanent snowline (about 6,000 ft).

On the east the vegetation is largely subalpine tussock with small areas of beech and totara forest in gullies and patches which have escaped destruction by fire, possibly set alight by early Maoris. Evidence for the former extent of the eastern forest is given by the widespread occurrence of charred logs of totara and matai, and charcoal horizons in the soil. Changing climate was possibly the reason for the failure of the forest to regenerate.

The most notable of New Zealand's flowering plants, the subalpine and alpine plants, are found in the Southern Alps. Generally the forest flowers are inconspicuous.