Indigenous species - Kahikatea, Dacrycarpus dacrydioides
Kahikatea is a native softwood, favoured for amenity and wetland restoration. It is found throughout New Zealand, tolerates cold and grows to altitudes of 600-700 m but is most commonly found in wet lowland forests. It once grew widely in North Island swamps and river flats, until these were cleared for farmland. Kahikatea is a relatively slow growing tree of narrow conical form, reaching 40-60 metres over 600 years. Its prolific fruit is favoured by kereru and tui.
Commercial return: Low
RainfallHigh rainfall; Moderately low rainfall;
WindStrong wind; Moderate wind;
Soil drainageModerately poor draining; Poor drainage;
Soil depthDeep; Moderate depth;
Kahikatea is a hardy pioneer species and establishes fairly easily in moist sites. Being light loving it can be grown in the open.
Prepare grass sites by spot spraying a one metre circle for each planting site. Use glyphosate herbicide with spray dye a few days before planting as this will not leave chemical residue in the soil. Prepare spots using straight lines and accurate spacings between spots so that trees can be easily found later. Cut down woody weeds and flatten these on the ground so they decay and don't support weed growth.
Trees are generally available from commercial nurseries as container grown or bare-rooted stock. Price per tree should range from $2.50 - $5.00 for 1-2 year-old contract-grown forestry stock.
Take great care in the handling, transport and storage of seedlings, especially bare-rooted stock which must be kept cool and moist and planted as soon as possible after wrenching. Containerised (plug) stock should also be planted as soon as possible after receiving the plants. Make sure the root plugs are moist by soaking in a water trough.
Plant trees with a slow release fertilizer tablet underneath or put a trowel of high nitrogen fertiliser such as DAP or urea in a spade slit above the seedling.
Do not "slit and stuff" bare-rooted plants. Plant as per these instructions ».
For containerised stock, dig a hole twice the size of the plant container, leaving some soft soil at the bottom. Tease out (straighten and trim) any pot-bound roots before firming the soil around them, ensuring there are no air cavities.
If the site has standing water in winter and stays damp or boggy over summer, plant in late spring to allow the plants to adjust to the wet conditions.
Recommended spacing when planting for timber is 2 x 3m or 2 x 2.5m (1600 - 2000 stems per hectare), thinned to 400 stems over 50 years. Alternatively, 800 - 1000 stems per hectare interplanted with 800 - 1000 stems per hectare of manuka.
- Prevent weeds from competing with the Kahikatea seedlings for at least three years after planting.
- Protect seedlings from browsing by stock and wild animals.
Ensure the newly planted tree gets enough light, moisture and nutrients to establish unimpeded. Maintain young trees by clearing or spraying weeds around them for at least two years or until they are well established and growing. Seek advice on choice of chemical if release spraying.
Native trees, being slower growing than exotics, may require releasing from weeds for several years so they don't become smothered by early weed competition.
During establishment Kahikatea responds to side shade by growing faster, straighter and taller with fewer branches. A nurse species that grows fast initially but does not grow too big, such as manuka, can be planted to provide side shelter. The nurse crop should ideally be planted a year or two ahead of the Kahikatea.
Overhead shade slows down growth. For good growth rates release trees from competing vegetation so some direct sunlight always reaches the tree’s leader. Climbing plants and dense woody weeds can overtop young native trees and may require manually cutting back to provide a light-well for the young tree to grow up through.
Where Kahikatea regenerates with manuka and gorse it will overtop these species within two or three decades, sooner if provided sufficient light.
Kahikatea is damaged if grazed by stock, goats and deer so fence the area to keep them out. A single hotwire electric fence will deter most cattle, but it is best to construct a full post and wire fence.
Young Kahikatea are palatable to hares and rabbits. They will slice off trees near ground level at a 45 degree angle, killing them. In spring and summer the trees are palatable to possums which should be controlled with poison, trapping or shooting.
Pests and diseases
Kahikatea is relatively disease resistant and not susceptible to insect or fungal attack.
Kahikatea is one of the easiest native trees to grow in the open and is usually planted for habitat and wetland restoration. Although it will eventually produce timber, high-value applications are limited.
Suitability for steep slopes: Kahikatea is prone to compression wood on exposed sites and is only suitable for moist micro-sites with reasonable soil depth. Kahikatea does not coppice: the stump dies when the tree is felled.
Grown in a natural stand, kahikatea shed their lower branches to produce long, straight trunks with buttress roots.
Form prune if it is necessary to remove competing leaders.
Clearwood pruning: The aim of clearwood pruning is to minimise the defect core and produce wood free of knots. Pruning "lifts" must be regular and undertaken at a frequency that minimises branch size and diameter over stubs (DOS). Ideally, only final crop trees would be clear-pruned. The smaller more horizontal branches on lower stems of Kahikatea established within a highly-stocked stand (i.e. 1600 stems per hectare or more) will generally self-prune when they are shaded out. Larger, upward pointing branches should be removed as soon as possible as they will reduce height growth and increase defect core diameter.
Clearwood pruning guidelines are available here.
Suitable pruning tools include loppers and a pruning hand-saw, a battery-operated reciprocating saw, or battery-operated loppers. Form pruning can be undertaken by using a pole pruner.
Close spacings provide better height growth and small branches but with a reduced diameter growth rate. Thinning is required to reduce stocking (number of trees per hectare) and encourage diameter growth in residual "crop" trees.
Thin once the canopy has closed and before the trees get too tall, e.g. at 8–9 m in height. Where kahikatea are planted at final spacing no thinning is necessary.
When to harvest
Well pruned kahikatea may be harvested for sawn timber once the diameter reaches 35cm diameter. Larger trees produce better grades and yields.
Kahikatea heartwood is white to pale yellow-brown and the sapwood creamy white. Sapwood can be boron treated to prevent borer attack but is not suitable for ground treatment with CCA preservative. The wood is easy to dry, light and easily worked, does not taint food, and carves well. Large older trees have historically provided long, clear boards that were used for weatherboards and boat building. Kahikatea is also suitable for structural applications.
Logs should be milled and sawn timber dried as soon as possible after harvest to avoid sap stain.
Markets and demand
Harvesting of Kahikatea is controlled by the Forests Act (and must be undertaken sustainably). Planted Kahikatea may be harvested for timber without controls if the owner has obtained a certificate from the Ministry for Primary Industries. The process is described here.
Kahikatea is not a commonly traded timber.
Kahikatea grows well in the open and is one of the fastest native forest species to establish from scratch. It is New Zealand’s tallest forest species. After 25 years kahikatea can reach 10 metres tall with trunk diameters of nearly 20 centimetres. After 50 years trees can be 20 metres tall.
This paper offers some advice on monitoring growth.
Timber return on investment
No published calculations show return on investment for growing Kahikatea for commercial purposes. Although a simple calculation suggests earnings from carbon credits might overtake the costs of establishment after 20 years, this calculation is sensitive to every assumption and no claim is made that it is true or accurate. The assumptions used were:
- Establishing 400 stems per ha at $5 per stem ($2,000 per ha)
- Cost of capital 5% pa real
- Lookup tables for indigenous forests apply: price of carbon $30 per NZU real
- Excluding the costs of land, rates, management and ETS compliance.
Carbon sequestration rate over time, and relevant Look-up Tables
If the land is registered under the Emissions Trading Scheme and the trees are planted so as to comply, i.e. at least one hectare, with tree crown cover of more than 30 percent in each hectare and an average width of tree crown cover of at least 30 metres, then they should earn carbon credits. The relevant look-up tables for determining how quickly they store carbon and earn credits, and guides to how to use the tables, may be downloaded here.
As Kahikatea is an indigenous softwood, tables A2.2 and A2.4 apply, suggesting that over its first 30 years Kahikatea stores carbon at a rate of approximately one third as fast as radiata pine.
Outside the ETS this carbon calculator suggests how much carbon a planted native forest will store over time.
- The Indigenous Forest Section of the NZFFA promotes sustainable indigenous forestry.
- Project Kahikatea, a special interest group based in the Waikato, is a good source of information.
- Tane’s Tree Trust provides information on indigenous forest species.
- Regional councils and the Department of Conservation identify and protect kahikatea remnants. In particular the Waikato Regional Council actively encourages replanting and the protection of existing stands, and has mapped over 3,000 examples of kahikatea stands totalling 2760 hectares.