20% of New Zealand will be invaded by wilding conifer forests within 20 years without rapid action. Wilding conifers currently cover more than 1.8 million ha of land, and are spreading at an estimated rate of 5% a year.
As wilding conifers overwhelm our native landscapes, they kill our native plants, and evict our native animals. They also have a huge impact on our economy. They suck valuable water out of catchments, they add big costs to farming and they impact on tourism and recreational opportunities.
The photos below were taken over 17 years from Mid Dome, Southland. They show how rapidly wilding conifers colonise the landscape when left unchecked. Once they form a closed canopy virtually all native plants are destroyed because they cannot grow in deep shade. Also the quantity of water flowing from the catchment is reduced by more than 40% through water vapour released to the atmosphere through the leaves of the trees.
Wilding conifer spread in 1998, 2004 and 2015 in Mid-Dome, Southland
Image: Environment Southland ©
What is a wilding conifer?
Conifers are woody plants that have cones instead of flowers. They include cedars, pines, firs, cypress, larches, and spruces.
Wilding conifer is the New Zealand term for introduced conifers that are spreading across the landscape – self-sown and unwanted.
They are unwanted because their timber either has no value or the extraction costs outweigh timber value. They often grow in mixed species groups.
Ten introduced conifer species are responsible for most of the wilding conifers.
- Two of these species, radiata pine and Douglas fir, are also important commercial species, but only when the trees are planted in an appropriate place, at suitable spacings, and tended as they grow.
- One species, the lodgepole (contorta) pine has been declared an unwanted organism under the Biosecurity Act 1993, which means it cannot be bred, propagated, distributed or sold.
Why are wilding conifers a problem?
When conifer cones mature on the tree, they open to release masses of wind-blown seeds. These seeds travel kilometres downwind and need no special conditions to take root and grow.
Wilding conifers are a major problem in areas where there is no native forest, such as above the bush line, in mineral belts and tussock grasslands. In these areas, wilding conifers modify the natural ecosystems so much that the unique New Zealand landscape is lost and native plants and animals are evicted or die.
In native forests, wilding conifers compete for space with native trees and plants and don't provide the advantages that native trees do, such as food for native birds or insects. Their needles form an acidic carpet which discourages regeneration of native forest floor species. They can be visually intrusive in native forest areas.
Which conifers are causing the wilding conifer problem?
Most wilding conifers are one of the species below. The links take you to more information on the New Zealand Plant Conservation Network website.
- European larch (Larix decidua)
A distinctive deciduous conifer, can be invasive in wetter areas.
- Lodgepole or contorta pine (Pinus contorta)
The most aggressive species with the youngest coning age and farthest spread. Has been declared an unwanted organism under the Biosecurity Act 1993 since 2001, which means it cannot be bred, propagated, distributed or sold.
- Dwarf mountain pine (Pinus mugo)
A short bushy species that was planted in alpine areas, has spread slowly, but is very hard to kill.
- Corsican pine (Pinus nigra)
Slower to mature than lodgepole or contorta pine, but can spread very large distances.
- Maritime pine (Pinus pinaster)
Very large tree that often grows in association with radiata pine in coastal areas.
- Ponderosa pine (Pinus ponderosa)
Historically grown as an amenity tree in very dry areas where it often spreads.
- Scots pine (Pinus sylvestris)
Bishop pine (Pinus muricata)
These two species have a bluish tinge, are rarely grown for timber, but have spread from early trial sites.
- Radiata pine (Pinus radiata)
The most common commercial timber species, but can spread in lowland situations and affect native bush regeneration.
- Douglas fir (Pseudotsuga menziesii).
The second most common commercial timber species, but can spread rapidly in montane areas.
How you can help
- Dispose of garden waste wisely, including discarded Christmas trees.
- Join a weed group that protects our unique landscapes and native plants and animals from wilding conifers.
- Prevent the spread of wilding conifers from land you manage.
- Help build a weed map of the distribution of wilding conifers by reporting observations on the iNaturalist NZ – Mātaki Taiao website. Take photos of the whole tree, plus close-up photos of cones, needles and bark, sign up to iNaturalist NZ – Mātaki Taiao, post the location, date, and photos. If you are not absolutely sure which species it is, tick the box 'ID needed'.
Identify wilding conifers
Use the New Zealand Plant Conservation Network website to see information about pines, firs, larches, cedars and spruces that have naturalised in New Zealand.
Use the species identification web page on the wilding conifers website to see a table showing the differences between the common wilding conifer species. You can also find a key to wilding conifers on this web page.
Note: You will need to install or update Java software to run the key, and it doesn't run on the Chrome browser.
Methods of control
Wilding Conifer Management Strategy
The right tree in the right place provides a framework for central government, local government, forestry and farming industries, landowners, researchers and communities to work together to reduce the negative impacts of wilding conifers.
Local groups with a focus on wilding conifer control
- Abel Tasman Birdsong Trust (Upper Marahau Valley, Nelson)
- Marlborough Sounds Restoration Trust (Marlborough)
- Waimakariri Ecological and Landscape Restoration Trust (North Canterbury)
- Ohau Conservation Trust (Mackenzie Basin, South Canterbury)
- Wakatipu Wilding Control Group (Wakatipu Basin, Central Otago)
- Central Otago Wilding Conifer Control Group (Central Otago) – contact our Alexandra office
- Mid Dome Charitable Trust (Southland)