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Advances in cypress research A summary of the activities of Specialty Wood Products

Marco Lausberg and Harriet Palmer, New Zealand Tree Grower August 2022.

The Specialty Wood Products research programme draws to close in 2022. Species included are Douglas-fir, cypress along with durable and non-durable eucalypts. This article is about the results of the cypress research.

 Two of the main objectives of the Specialty Wood Products programme can be summarised as being to –

  • Develop new processing and product options to make the most of existing specialty species growing in New Zealand
  • Make breeding gains to encourage new planting of specialty species to ensure a sustainable supply in future.

Total investment in cypress research in this programme from 2015 to 2022 is over $960,000. The research is in five main areas, shown in the table.

Expenditure on breeding research is supported because of the continuing demand in New Zealand for quality timber used in indoor and outdoor joinery along with other high-value applications. Processing and durability work is justified to make the most of the approximately 10,000 hectares of cypress growing in New Zealand. The existing cypress processing industry has been based on old macrocarpa trees, the supply of which is now almost exhausted. New processing and product options are needed for what is predominantly a young, growing resource.

Cypress breeding

Almost half the spend on cypress over the past seven years has been in breeding research. Scion has led the breeding work, with a big input from Toby Stovold and colleagues.  The NZFFA’s Cypress Development Group has also become heavily involved.The work has built on earlier work by the Forest Research Institute which left a legacy of a large nationwide trial network with over 500 permanent sample plots still surviving in cypress stands.

The decline in the popularity of macrocarpa from the perspective of New Zealand forest growers, is understood and well-documented. New Zealand tree breeders have long been looking for canker-resistant macrocarpa, as well as testing closely related alternatives to macrocarpa – predominantly various C. lusitanica Mexican cypress, including the now relatively popular Ovens cypress Cupressocyparis cv ovensii, a hybrid of C. lusitanica and Chamaecyparis nootkatensis.

The investment in cypress breeding is leaving its own legacy, having completed all or part the following –

  • C. lusitanica progeny trials were evaluated for growth and health, with new selections made to include seed orchards, bringing new seeds to industry over five to seven years.
  • The third generation of C. lusitanica trials established in 2017.Two are new trial series established in the past three years with large-scale trials to test new C. macrocarpa genotypes identified as potentially canker tolerant and a series of small-scale trials to test 12 Ch. nootkatensis hybrids, managed by the Cypress Development Group and planted across a range of properties in 2021 and 2022.Trials will continue to be established with promising varieties promoted.

The Cypress Development Group has worked closely with Scion to establish hybrid trials over the past few years. They have also identified several strains of C. torulosa Himalayan cypress, which are being trialled with a view to producing the next generation of planting material. Ch nootkatensis and C. torulosa both appear to be canker resistant, with growth and form of some trial trees looking promising.

Growers are already benefitting from the new seedlings and clones being made commercially available, with more to come.The estimates are that there will be 100,000 plants for the 2023 planting season.The Cypress Development Group has also been experimenting with using tissue culture to propagate planting material, which in theory could lead to mass production, should there be sufficient demand.

The Specialty Wood Products research programme, a seven-year partnership between Forest Growers Research, the Ministry for Business, Innovation and Employment, research providers and industry partners, draws to close in 2022. The August 2021 Tree Grower provided an overview of Specialty Wood Products objectives and activities. An important recent product is Cypress Industry Strategy 2022-2042, produced by the NZFFA’s Cypress Development Group.

Processing and durability

Much of the cypress research on processing and durability has been led by Scion wood scientist Rosie Sargent. Practical processing research has included the work to investigate the timber potential of young, unpruned and un-thinned cypress. Specimens of two cypress clones, one C. lusitanica and one C. ovensii, growing in a 22-year-old trial, were harvested and taken to Ruapehu Sawmills for milling. Volume recoveries were high with 51 per cent of logs harvested converted into graded timber. Over 90 per cent of the boards reached the top appearance grade.

If this timber can be made durable using thermal modification, as now seems possible, then it will open up multiple market opportunities.  This provides encouragement to advocates of relatively short rotation, low-cost cypress regimes.

Two projects associated with this sawing study have also been completed. One is the construction of economic models of C. ovensii clonal regimes grown on short rotation no-prune, no-thin cypress regimes.  The Cypress Calculator was used to analyse permanent sample plot data from a range of sites supplied by industry. Some options appeared to be profitable depending on site productivity, log prices and starting land values.

The other project used sawn C. ovensii timber from the grade recovery trial which was tested for bending strength and stiffness by Scion. In terms of bending stiffness, the C. ovensii achieved SG 6 structural grade.  In terms of bending strength, it achieved SG10 structural grade, resulting in an overall grade of SG 6.  A full suite of structural grade tests will need more timber, but these tests were a useful starting point to understand the potential applications. High-value joinery is considered the preferred potential end use, rather than framing or other load-bearing applications where structural grade is critical.

Durability research has focused on thermal modification of C. lusitanica. This involves heating timber to 220 °C and then testing the effect of this on durability and other properties.

Short duration and long-duration tests are used to determine durability.The interim 12-month fungus cellar results for C. lusitanica are very promising with modified heartwood and sapwood both showing increased durability over unmodified heartwood.  They show similar durability to H3.2 treated radiata pine. Outdoor tests are under way.

Work on the dimensional stability of species, including cypresses, has also been completed.  Dimensional stability is critical in terms of how wood performs in service.

Woodscape models

As part of the broader programme, Scion’s Woodscape model has been used to assess the technical and economic potential of processing specialty species under a range of options.

Three analyses have been completed and provide early guidance on how future investment in processing could be made viable.The reports are recommended reading for anyone with an interest in developing specialty species supply chains.

The first report Identifying processing opportunities for key specialty tree species – resource analysis uses National Exotic Forest Description data for cypress, eucalypts and Douglas-fir to model regional wood flows up to the 2060s.This information is an essential precursor to running the Woodscape model as the economics of different processing options depend on the location and long-term stability of the wood supply.


The information outlined above was an important part of detailed regional technical and economic analysis of probable small-scale processing and drying options for Douglas-fir, E. nitens, C. macrocarpa and C. lusitanica. The best performing options were a small-scale cypress sawmilling option, around 5,000 cubic metres a year using solar kilns, and a similar E. nitens option but which was more sensitive to log prices.

A third report based around Woodscape was an analysis of producing thermally modified wood products from specialty species Techno-economic analysis of producing engineered and thermally modified products from specialty wood species.  This concluded that a medium-scale processing operation with an intake of around 9,200 cubic metres a year, could produce thermally modified cypress cladding and generate a return on capital of 30 per cent and an internal rate of return of 16 per cent. This compares favourably with a range of other processing options for Douglas-fir and E. nitens.The cypress operation would require an estimated 75 hectares of forest to be harvested annually, meaning a total area of around 3,000 hectares of mixed-age forest to supply the operation.

An associated Woodscape report was produced for Hawke’s Bay Regional Council.  This used Wairoa as a case-study of a potential location for a specialty species processing operation.

Together these reports have under-pinned the concept of growing the specialty species industry in New Zealand via a network of planned regional wood supply catchments. In these, new planting and investment in processing would be encouraged with support from regional authorities and forest growers. A small-to-medium scale wood processing operation or hub would be located at the centre, each requiring 3,000 to 5,000 hectares of forest to be planted over approximately 30 years.

Up to 40 catchments spread throughout New Zealand could be established, each central hub having good transport links and a nearby population centre from where labour could be obtained.This concept may well form the basis of a future research and development programme.

The cypress strategy 2022 to 2042

The Specialty Wood Products original objectives included developing a series of business cases. In the case of cypresses, a business strategy has been produced, led by the Cypress Development Group. New Zealand Cypress Strategy 2022-2042:Whakamahere Cypress is available on the Forest Growers Research website.

Producing the strategy involved a number of stages.  The first two involved consultation with large-scale growers, processors and the marketing sector, followed by a workshop which brought together large and small- scale growers, harvesting and marketing professionals, processors and retailers.The workshop identified the industry’s strengths and weaknesses. Six main themes for future research and development work on cypress were agreed –

  • Implementing a cypress forestry research plan
  • Modelling forest productivity and economic feasibility
  • Educating growers on cypress forest management
  • Identifying markets for cypress timbers of all types
  • Working regionally to encourage new cypress forests
  • Building industry partnerships to enhance support and capability.

The strategy identifies immediate, five-year and 10-year research and development priorities under the headings of – cypress breeding, site productivity and growth models, silvicultural practices, erosion mitigation, carbon sequestration, market access and wood quality. The Cypress Development Group plans to lead this work.

Overall summary

Development of all parts of the supply chain will be critical for the survival and growth of the cypress industry. Cypress have the advantage of already being an accepted and sought-after timber. For the cypress industry to succeed, a sustainable supply of good quality timber is needed. If this is to happen, growers need to be confident of a competitive return on their investment, which in turn should motivate them to plant more.

The gains made in cypress breeding by the programme over the past seven years will increasingly contribute to providing growers with planting material they can have confidence in.  The Specialty Wood Products’ processing and durability research has filled gaps in the knowledge of the suitability of cypress timbers for traditional and new markets.The Woodscape modelling work provides a much greater understanding of wood flows, processing capacity and the magnitude of investment in processing required for a sustainable specialty species industry to develop. Finally, the work that went into developing the cypress strategy provides a clear way forward and identifies priorities for the cypress industry.

Cypress-related technical reports

All the technical reports referred to in this article are freely available on the Forest Growers Research website. They contain a wealth of further information.

Marco Lausberg is Programme Manager of the Specialty Woods Products Research Partnership. Harriet Palmer is an independent forestry communications specialist.


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