The uniqueness of New Zealand plants
New Zealand plants are unique! New Zealand has some of the oldest primeval forests in the world, the largest type of moss and some of the largest tree ferns found anywhere. Many of the species are very similar to those growing on Earth in the time of the dinosaurs – and even earlier.
Aotearoa separated from Gondwanaland approximately 85 million years ago. The separation from Australia left New Zealand at least 2,000 km away 55 million years ago. This isolation from other land masses meant that, until humans arrived, plants were not replaced or competed with by other species from elsewhere. They continued to evolve alone – in this unique environment.
New Zealand’s changing coastline
Over millions of years, New Zealand as a land mass has altered in shape and size, due largely to sea level changes, tectonic activity and glaciation.
Many plant varieties are related to plants found elsewhere – both in the northern and southern hemispheres. Fossil records also show that many of New Zealand’s plants are similar to those that were living on Gondwanaland.
However, our indigenous flora and fauna have also had time to evolve into unique species: 82% of New Zealand plants are endemic – they are not found anywhere else in the world.
Tānekaha
Tānekaha (Phyllocladus trichomanoides) is a New Zealand native tree that shows a very ancient characteristic. The leaves shown in this image are actually short shoots – modified stems called phylloclades – that are adapted for photosynthesis.
Geological processes such as tectonic activity, erosion and glaciation as well as climate change and sea level changes have altered the coastline of New Zealand in the past. As a result, over millions of years, New Zealand has been a series of islands, a larger landmass, largely underwater or under ice.
The changes to the land forced a process called speciation: animals and plants with useful adaptations survived. Eventually, these animals and plants become so different from their ancestors that they were no longer able to reproduce with the ancestral species. They had become new species.
Aotearoa New Zealand also has many examples of regional endemism – where animal or plant varieties are found only in restricted locations.
New Zealand’s botanical regions
Over millions of years, New Zealand has developed unique regional environments. These environments are shaped by factors such topography and climate, and influence the botany of the area.
Some specific adaptations of New Zealand plants
Many native shrubs have a characteristic growth form called divarication. This is where the plant grows in a tangled way, with interlaced stems and small leaves. There are several ideas about why this is useful, but the dominant theory is that divarication may be a protective mechanism. The leaves are tucked inside and therefore less accessible for browsing animals and less prone to damage from frost or snow.
Divaricating coprosma
Divarication is a growth form characteristic of many New Zealand plants where the leaves tend to be small and the stems grow in an interwoven manner. Pictured is Coprosma rhamnoides.
Many flowers are small and white. New Zealand has a more limited range of pollinators compared to the rest of the world. Plants have evolved with animals, and the flowers have become specifically adapted to particular pollinators. Many of our pollinators are moths, small native bees, lizards and crawling insects that are not attracted by colour but by scent – so having showy flowers is unnecessary.
Most trees are evergreen. New Zealand did not undergo the extreme ice ages of the northern hemisphere, and as a result, not many of our trees are cold tolerant. They don’t have the protective adaptation of losing leaves in the winter as many northern hemisphere trees do. Only 11 species of New Zealand plants are deciduous – losing their leaves over winter.
Many of our trees are dioecious. This means they have flowers on separate male and female trees. A much higher proportion (12–13%) of New Zealand tree species are dioecious compared with other parts of the world (less than 5% in the UK). There is increased possibility of genetic variation carried in the seeds of dioecious plants. Genetic variability provides more likelihood of survival in a changing environment. The disadvantage of having separate male and female trees is that, if they are too far apart, it is more difficult for the pollen to be carried from the male to the female, reducing the likelihood of seeds forming.
Rimu Dacrydium cupressinum
Rimu are an endemic New Zealand podocarp tree that can reach up to 50 metres in height. It is a dioecious plant, with the male and female cones on separate trees and the seeds take 15 months to mature after pollination. The trunk of this rimu tree is covered with rata vines (metrosideros).
Many of our plants are highly variable in their form. This often makes identification difficult. Some have slightly different forms depending on the environment they are growing in – this is called heterophylly. Hybridism is also common – where plants of different species in a family cross-pollinate, creating new varieties. Many New Zealand plant families such as the Veronica genus (formerly Hebe) now include many species.
Variety in Veronica species
The Veronica genus (formerly known as Hebe) is a large group of New Zealand plants demonstrating wide variation. They hybridise (cross-pollinate) very easily and are adapted to very different environments. Two very different varieties are shown in this image – koromiko (Veronica salicifolia) on the left and Bentham’s hebe (Veronica benthamii) on the right.
Many plants have very different juvenile and adult forms. This is called heteroblasty, and the different form at each stage of the plant’s life provides an advantage, for example while it is growing.
Lancewood/horoeka
Many New Zealand plants have different juvenile and mature forms. The juvenile leaves of the lancewood/horoeka (Pseudopanax crassifolius) are long, thin and tough. The mature horoeka is bushier, with softer, wider leaves.
Juvenile and adult images sourced from iNaturalistNZ. Licensed under CC BY-NC 4.0.
Endangered plants
Animals and plants evolved together within the environment, and over time, unique and finely tuned ecosystems developed in New Zealand. In many of our ecosystems, the organisms became so interdependent – relying on each other for food, habitats and life processes such as pollination – that any changes could be detrimental. These changes are easier to see with iconic species of animals but may be less obvious in the plant world. However, many of our plants are now endangered. Deforestation caused a huge reduction in habitats, as did the introduction of other organisms into the New Zealand environment.
Many introduced plant species have become weeds, which can either outcompete native plants for habitat (wilding pines) or have a direct negative impact on the plants themselves (old man’s beard). Predators and other introduced wildlife can destroy pollinators such as birds or lizards or successfully compete with them (stoats and possums) or impact negatively on the plants themselves (mice eating native seeds).
Nature of science
This article highlights the ‘Understanding science’ aspect of the Nature of science – it illustrates how scientists use evidence to create theories about why New Zealand plants are so unique.
Related content
Resources for further information include Dragons in the mist, New Zealand’s unique ecology, Our changing ecosystems – timeline, Ecology of New Zealand and the video Green Antarctica and the New Zealand connection.
Teaching about native trees? Our native trees recorded PLD session introduces useful resources and activities about New Zealand's native trees. The webinar He rauemi reo Māori mō ngā rākau – Te reo Māori plant resources provides an overview of the bilingual suite of resources created with botanist Dr Norm Mason.
Many of New Zealand’s iconic wetland plants are endemic. Learn about plant zonation and how they've adapted to live in saturated soils.
Find out why New Zealand is home to so many divaricate plant families in How the Ice Ages spurred the evolution of New Zealand’s weird and wiry native plants.
The Connected article The war on weeds, describes how school students helped scientists combat the spread of weeds using the iNaturalist citizen science tool.
Teaching in te reo Māori? We have a series of articles exploring trees available here.
In the recorded webinar Exploring mātauranga in the classroom – Chloe Stantiall, a year 5–6 kaiako at Silverdale Normal School, shares her experiences and insights from a week-long teaching and learning sequence about kōwhai.
Useful links
There is a range of useful resources for further reading about native plants. These include books by authors such as Andrew Crowe, John Salmon, John Dawson and Tony Foster.
Websites such as Manaaki Whenua – Landcare Research, Department of Conservation and Bushmansfriend all provide detailed information about New Zealand native plants.
The Department of has recently produced a report on our endangered plant species – New plant status report shows increased threats – and kauri has now been reclassified as a threatened species, mainly due to kauri dieback disease.
Find out about The prickly prize of ongaonga (native stinging nettle) in this RadioNZ Our Changing World programme from September 2022. Native butterflies like the kahukura/red admiral rely on the sharp barbs of ongaonga (Urtica ferox) to provide a safe haven for their eggs and larvae.
