In general, tropical countries have a wider range of plant species than similarly sized countries with temperate climates. This rule holds for temperate New Zealand, which has only 2,500 native plant species. Most grow nowhere else. Included are 185 grasses, 93 hebe species and 20 conifers. Some 5,800 species of fungi have been given names, as have at least 2,000 lichens and 500 mosses.
Although Māori had names for most plants, the first European botanists to visit the country had difficulty putting names to some as they were so unlike any they had seen.
New Zealand has two main forest types:
- Southern beech forest – from Northland south to Fiordland. It grows mainly on the drier eastern side of mountains, on foothills and in the cooler south. Beech can grow in very poor soil, and often covers ridges and mountain tops.
- Conifer–broadleaf forest – throughout New Zealand. It grows mainly on the wetter western mountainsides and in deeper gullies and foothills. Kauri forest is considered a subset of conifer–broadleaf forest,and grows from Coromandel Peninsula northwards.
These forest types often intermix.
Conifer–broadleaf forest resembles tropical jungle rather than European woodlands. Most of the trees have thick, shiny, evergreen leaves. Several species have buttressed trunks, and flowers on their trunks or stems. Like rainforest, conifer–broadleaf forest is many-layered, with tall, emergent trees. A closed roof or canopy of tall trees blocks out most of the light. Beneath are layers of sub-canopy trees and tree ferns, then a shrub layer and finally a dense layer of ferns, seedlings and other ground plants.
Contributing further to the appearance of tropical rainforest are a tangle of scrambling, climbing, hanging and perching flowering plants, ferns, mosses, lichens, liverworts, algae and fungi.
Flowers and fruit
The amount of berries, fruit and seeds produced by plants in the bush varies from year to year. A warm summer and heavy flowering is usually followed by a bonanza crop of berries, fruit and seed the following autumn. Cold summers suppress flowering and fruit production.
Several plant species are known as ‘periodic flowerers’, as they produce few flowers or no flowers at all for a year or two, then produce vast numbers. Five species of southern beech tree, along with cabbage trees, flax, and the climbing kiekie are periodic flowerers, producing heavy crops of seed every two to four years. Some birds have evolved to be periodic breeders in response.
Relatives of many of New Zealand’s most distinctive trees, such as rimu, kahikatea, miro, tōtara and beech, were present when New Zealand was part of Gondwana. Some biologists used to think these trees evolved from ancestors that were ‘on board’ when New Zealand broke away from Gondwana 85 million years ago. Others now argue that these species’ ancestors disappeared from New Zealand for a while, only to be re-introduced from Australia or New Caledonia.