Cedar - Japanese cedar, Cryptomeria japonica
Japanese cedar (“cryptomeria”) is a large, temperate conifer native to East Asia. It does not like dry conditions, but tolerates frost and wind and does best in well drained, deep soils at altitudes of up to 600 metres. With an elegant conical form it is commonly planted as an ornamental, or for shelter. Many small blocks have been successfully planted by farm foresters. It will grow for over 2,000 years reaching 70 metres high and 4 metres in diameter with a narrow conical form.
Commercial return: Medium
RainfallHigh rainfall; Moderately low rainfall;
AltitudeModerate altitude; Low altitude;
WindSalt laden, strong wind; Strong wind; Moderate wind;
Soil drainageFree draining; Moderately free draining;
Soil depthDeep; Moderate depth;
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.
Japanese cedar requires a site with good rainfall.
Container-grown and bare-rooted stock is available from some commercial nurseries; Price per tree should range from $0.80 - $2.00 for 1-2 year-old contract-grown forestry stock.
Japanese cedar prefers reasonable soil depth and evenly distributed rainfall. Japanese cedar will grow well in most soils, but does not tolerate poor soil drainage. Young trees are shade tolerant, but are slow starters so need reasonable weed control during establishment. Plant in winter.
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.
When growing cryptomeria for timber plant at a relatively high stocking to ensure a high selection ratio of vigorous final crop trees and to encourage narrow form and fine branching. A suggested initial stocking is 1670 stems per hectare (2 m x 3 m), but lower stockings of down to 833 stems per hectare (4 m x 3 m) are acceptable. The natural form of this species is narrow conical and so branching isn't too heavy at low stockings.
- Prevent weeds from competing with the Japanese cedar seedlings for at least two years after planting.
- Protect seedlings from browsing by stock and wild animals.
Japanese cedar is shade tolerant but establishes much faster with good weed control. Release spray after planting once weeds begin to regrow. Spray releasing for the first two years is recommended for good growth rates.
Japanese cedar is palatable to deer and stock and all stock should be permanently fenced out as the tree has a thin bark, which is easily damaged.
Young Japanese cedar seedlings are palatable to hares and rabbits. They will slice off trees near ground level at a 45 degree angle, killing them.
The seedlings may be palatable to possums which should be controlled with poison, trapping or shooting.
Pests and diseases
In New Zealand Japanese cedar is generally healthy and rarely harmed by insects, disease or frost. Severe drought conditions can kill the trees. If planted in ground that can become waterlogged, it will be susceptible to root-rot.
Japanese cedar is a relatively fast growing conifer with a tall, narrow habit. While common in forestry plantations in Japan and China, here it is mostly used for shelter. Japanese cedar has a strong root system that resists windthrow and it filters the wind rather than creating a solid barrier that creates turbulence on the windward side.
Suitability for steep slopes: Grown for timber Japanese cedar is very productive over long rotations, lending itself well to steepland regimes for controlling erosion. Japanese cedar is tolerant of the extremely strong winds prevalent on steepland sites. Japanese cedar does not cause wilding spread and being shade tolerant will regenerate in light wells, making it very suitable for continuous cover forestry (i.e. where individual trees are harvested on reaching a particular size rather than a particular age). When grown for timber the target is to achieve large pruned butt logs and upper unpruned logs with green or moribund branches less than 50 mm diameter. Because of its narrow conical form and shade tolerance this species is one of the easiest to grow for timber production, and at a final stocking of 400 stems per hectare will produce sawlogs with good diameters.
To get good quality timber suitable for cladding, silvicultural management should aim to minimise the incidence of bark-encased knots.
Japanese cedar has good form with few malformations or double leaders. Japanese cedar will grow tall and lightly branched. To develop quality clearwood Japanese cedar requires pruning.
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 Japanese cedar 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.
Prune the stem in 3 to 4 lifts (depending on site productivity) to a stem diameter of 12 cm, and to at least 6 metres height. Prune annually from approximately age 5 or when 2-3 m tall, then every year or two after that.
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.
Japanese cedar has a narrow conical form with small abundant branches that are reasonably shade-tolerant. Because the target product is the naturally durable heartwood, thinning should aim for a final crop of evenly spaced trees of around 400 stems/ha and a 35-40 year rotation. Thinning should commence once crowns touch and before branches die from shade.
When to harvest
Growth rates vary around the country. They can be as much as 1 metre a year in height and 2 cm a year in diameter, but in general allow one year for each cm of diameter growth. To get to an acceptable 40 cm diameter butt log plan on a rotation of 40 years.
Grown for erosion control on steep faces as a permanent forest, Japanese cedar could be harvested as soon as it reaches 45 cm diameter at breast height, which could be between 30 and 50 years depending on site conditions.
Japanese cedar timber is pleasantly scented, reddish-pink in colour, lightweight and resistant to decay. It is easy to saw and season with good woodworking properties, and is favoured for its appearance. It is used in joinery, boxes, panelling, veneers, plywood and furniture. The heartwood is suitable for exterior cladding but is not accepted in New Zealand as a structural timber. Find out more about the timber here »
Markets and demand
Cryptomeria is sawn and marketed as cedar. A handful of mills around the country have developed a small market for ‘cedar’ timber, especially for weatherboards and exterior cladding.
While Japanese cedar is one of the largest volume producers of any plantation softwood, yield data from older blocks planted for timber is variable, as the stands have been affected by site conditions, high stockings and neglect. The best growth has been in the central and northern parts of the North Island, where cryptomeria can grow at 1 m per year in height and 2 cm per year in diameter. One plantation near Gisborne stocked at 940 stems per hectare gave an average height of 18 metres and diameter of 38 cm at age 19. No formal growth models exist for local conditions.
Practical hints for measuring trees offers some advice on monitoring growth.
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 Japanese cedar is an exotic softwood tables A2.2 and A2.4 apply, suggesting that over its first 30 years it stores carbon roughly 1 1/2 times faster than indigenous forest and half as fast as radiata pine.
Timber return on investment
There are no economic analyses of Japanese cedar grown for timber in New Zealand, but based on productivity and export log prices it would likely be similar to Douglas fir.