Farm Forestry New Zealand

Macrocarpa is best grown in cooler southern slopes with regular rainfall on well-drained soils. It is reasonably shade tolerant but grows fastest in open sites with some sun.

Planting

Macrocarpa seedling planting stock is available from many commercial nurseries, either bare-rooted or containerised. Price per tree should range from $0.50 - $1.50 for 1 year-old seedling forestry stock (2020 prices). Containerised stock is usually more expensive than bare-rooted. Improved cutting-grown cultivars are being developed.

Plant bare-rooted stock in winter. Containerised stock can be planted from autumn to spring. The planting site should be free from weed competition.

Although tolerant of extreme winds, macrocarpa prefers some shelter and is prone to toppling on some sites. This happens if root growth is too slow in relation to top growth, and may occur in the first 3 years after planting. It appears to be worst on fertile farm sites and soils with slow drainage such as heavy clays, where the effects of wind and rain combine to cause windthrow.

A short video is available on planting of cypresses.

Spacing

When growing macrocarpa for timber use a relatively high stocking to ensure a wide choice of final crop trees and to control branch size. Initial stocking should be 1,600 stems per hectare (2.5 m x 2.5 m).

Releasing

Macrocarpa is vigorous as a young seedling and soon overtops competing weed species. Release spray after planting once weeds begin to regrow. Avoid further release spraying if possible and manually release trees that require it. Spray releasing increases growth rate which should be avoided, because early growth results in toppling.

Terbuthylazine is used at radiata pine rates and haloxyfop is useful on sites dominated by grasses and especially tropical grasses such as kikuyu, paspalum and cocksfoot.

See Successful establishment of tree seedlings »

Grazing/Browsing

Stock should be fenced out permanently. Cattle, goats and deer will strip the bark off trees and kill them. As cypresses can cause abortion in pregnant cattle, keep trees well back from fence lines if cattle may graze adjacent land.

Young macrocarpa seedlings are palatable to hares and rabbits. They will slice off trees near ground level at a 45 degree angle, killing them.

Possums can ringbark the tops of mature trees. They should be controlled with poison, trapping or shooting.

Pests and diseases

Cypresses have few health issues. Some macrocarpa strains are susceptible to canker, a fungal disease that can cause branches and leaders to die. Cooler conditions may limit the development of cypress canker, but of most importance is to source seedlings that are a canker-resistant variety.

See Pests and diseases of macrocarpa »

Many blocks of macrocarpa have been planted by farm foresters for cypress timber, which is attractive and durable. To produce good quality logs growers should aim to minimise the incidence of bark-encased (dead) knots. For clearwood production macrocarpa is normally grown on rotations of 35-40 years, although useful small diameter sawlogs may be harvested sooner.

Suitability for steep slopes: Macrocarpa provides effective erosion control on erodible hill country. It does not coppice but its roots are slow to decay upon harvesting, reducing the risk for erosion to occur before the next crop is established. Macrocarpa will carry a higher basal area per hectare than radiata pine and because it is reasonably shade tolerant, it is suitable for selective harvesting / continuous cover forestry.

Pruning

Macrocarpa naturally grows lots of branches. For veneer logs or long clear lengths of lumber the trees will require regular pruning. The technique is shown in these short videos:

• Pruning cypresses – low pruning (first lift)
• Pruning cypresses – medium pruning (second lift)

Trees grown for high-quality timber should be pruned annually from year four. Prune for a diameter over stubs (DOS) of no more than 15cm, remove 50-60% of the green crown at most and try not to damage the bark, which is thin. Pruned height should be between 4.5m and 6.5m.

Thinning

To encourage the best timber trees the poorly-formed ones should be thinned once the crowns begin to touch, and before the lower branches start to die and create dead knots that downgrade the timber. Thin at least twice, but to minimise the risk of windthrow thin little and often. Thinning should aim for a final crop of evenly spaced trees of between 200 and 400 stems/ha depending on the target log diameter and rotation length. Thinning is explained in this short video Thinning cypresses ».

Production thinning – i.e. selling the thinned stems as small sawlogs (e.g. 15–20 cm in diameter) – may be an option because macrocarpa as young as 15 years of age generally mill well. However logs from thinnings do not return much value to the grower and these have little heartwood.

When to harvest

Given timely pruning and thinning, macrocarpa will produce trees with a mean diameter at breast height of 60 cm on rotations of 35 - 40 years, although unpruned sawlogs may be harvested sooner. Because it is a shade tolerant species macrocarpa is suitable for continuous cover forestry where the trees are harvested when they reach a target size, rather than a target age (i.e. “target diameter harvesting”).

Macrocarpa is a medium density, durable softwood. The timber is moderately stiff and strong but fairly soft. It has a fine, even texture; a decorative, subtle grain, good colour, figure and lustre; good machining properties and finish, and excellent dimensional stability. It is easy to air dry but kiln drying requires care. Macrocarpa has been used in New Zealand for furniture, boat building, veneers, interior and exterior joinery, weatherboards, and farm utility timber. It is resistant to common borer and its offcuts make good firewood.

The heartwood is durable, but cannot be pressure treated with water-based preservatives such as CCA. Heartwood does not require treatment for structural applications and the sapwood can be boron treated to Hazard Class H1.2. Untreated heartwood can be used for exterior cladding and weatherboards, along with interior framing and finishing. In general cypress is suitable for exterior exposed, but not in-ground, applications.

See the short video Milling and markets for cypress timber »

Markets and demand

Cypresses are amongst the most valuable softwoods traded on the international market. There is a strong demand for cypress timber in Asia, and this is not likely to diminish in future. To date, stumpages for good quality New Zealand cypress have usually been about twice those paid for radiata pine of the same quality, but few good logs have been available.

Plantation grown macrocarpa can be fluted (the trunk develops an irregular cross-section), which reduces the log price because the usable volume from the logs is less for sawing or peeling. However cypress timber is in reasonable demand around the country and a handful of mills have developed a small Marketplace for it.

Macrocarpa can grow at 80 to 150 cm a year with a diameter growth of >2 cm. At age 10 trees may be 8 m to 12 m tall with a mean diameter at breast height of 15 to 25 cm. Stands on reasonable sites will put on volume of 20 m³/ha/annum or more, and trees with a mean diameter at breast height of 60 cm may be produced within 35 to 40 years.

Using sample plot information the industry has developed an interactive growth model for cypress. This is available as the Cypress calculator.

Practical hints for measuring trees offers some advice on monitoring growth.

As macrocarpa is an exotic softwood tables A2.2 and A2.4 apply, suggesting it stores carbon roughly 1 ¹/₂ times faster than indigenous forest and half as fast as radiata pine.

Timber return on investment

Published economic studies of cypress forestry have shown a range of values, reporting IRRs (internal rates of return) from 4 to 8% pa excluding land costs and carbon revenues. In comparison, the same studies calculated radiata pine returns ranging from 4 to 9.9% pa. Be aware that cypress forestry is not as mature and well researched as radiata pine forestry, which means that there are more assumptions involved and less certainty around the results.

• Members of the Cypress Development Group grow and research macrocarpa.
• Cypress - Information resources