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About Tenco
Tenco is one of New Zealand’s largest exporters of forest products. We have built to this position since 1991 when the company was set up to export lumber to growing Asian export markets.  Experience and reputation count; from small beginnings Tenco has become the largest independent exporter of New Zealand lumber and New Zealand’s 4th largest log exporter.  Tenco has a regular shipping program of their own log vessels and in combination with these and other ships currently calls  at 7 New Zealand ports (5 North Island and 2 South Island).
Tenco buys standing forests. Tenco regularly buys smaller tracts of forest to harvest immediately or immature forests to hold until harvest time. A deal with Tenco is a certain transaction. The owner and Tenco will agree on a value of the tree crop and then Tenco will pay this amount to the owner either in a lump sum amount or on rate per volume unit out-turn from the forest depending on the nature of the tree crop.

Tenco is actively interested in buying harvestable forests or trees from areas including all the North Island (except the Gisborne and East Coast districts) and Nelson & Marlborough in the South Island .
If you own a forest in this area (16 years and older) and are ready to enter into this kind of agreement Tenco is interested to develop something with you.
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Why I became, and remain, a clearwood advocate

Wink Sutton's Blog
Friday, October 04, 2019

Only recently have I become aware of the concept of unique special product or proposal. However, I now realise that for most of my forestry life I have been seeking to find how New Zealand’s radiata plantations can be managed to grow our own unique special product or USP.

I have long been aware that attempting to grow a commodity is most unlikely to be our best strategy. It is far better if we are able to produce a quality product that other species or other countries are not able to produce. I now find that while my vision is generally supported by small plantation owners, especially those who are distant from log markets, my USP vision is not shared by the large plantation owners of the central North Island.

First, some history and my early involvement with radiata clearwood. The first sawing of our plantations in the first half of the 20th century produced sawn timber which was full of knots, often large dead knots. Some trees had long internode logs or were of true uninodal form from which at least four feet, 1.2 metres, of clear cuttings could be sawn for the production of factory grade sawn timber or peeled for the production of knot free surfaces on plywood.

In the mid 20th century it became obvious to New Zealand forestry planners that, although the nation’s indigenous forest had for more than a century been the source of large mature trees which produced an abundance of clear sawn timber, that supply would eventually be either exhausted or put into reserves which prevented harvesting.

We owe an enormous debt to Stan Reid and Mat Grainger for their early advocacy of pruning our plantations. Stan Reid maintained that when it was defect free or clear, our radiata was the equal of old growth ponderosa pine from the West Coast of the USA.

Pruning needed

In 1959 the NZ Forest Service economist Mat Grainger was aware that, before indigenous sawmillers were granted a licence for the current year, they had to provide a return on volumes of indigenous tree species by sawn timber grades they had sawn in the previous year. Mat asked the Forest Service Head Office Timber Sales Branch, who held those sawmill returns, if they could use them to calculate the percentage of indigenous saw timber cut that was clearwood or defect free. I was a third year Forest Service trainee in 1959, seconded to work part time in the Timber Sales Branch. I was asked to undertake the task of data extraction and collation for Mat.

From what I remember just on half of the indigenous timber cut was heart dressing A grade − in other words quality clearwood. Mat used my calculations to advocate that if New Zealand was to have an equal volume of locally produced long length clears, the state plantations must all be pruned. The private sector which controlled about half of the nation’s plantation was generally not interested in pruning. Mat assumed that because we used a large volume of indigenous clearwood our plantations had to be a replacement source of supply. Indigenous clear saw timber was supplied so cheaply that this top grade was often used wastefully – for example as minor construction jobs like chicken coups.

Pruning evaluation

Because of the sirex wood wasp epidemic from 1945 to 1955 in our maturing radiata pine, and along with our past concentration on radiata, most new state plantings in the 1940s and the 1950s were of Douglas- fir, Corsican pine and Ponderosa pine along with a few other tree species. As most of our radiata pine plantations were then too old to be pruned, pruning was generally restricted to tree species other than radiata. For most of the next three decades pruning became an act of faith in many state plantations.

In the summer of 1960/61 I was assigned to the Forest Research Institute and asked to evaluate pruning of Ponderosa pine in Karioi forest. I have no idea why I was selected to do this as I had done no real research before. The evaluation was to follow George Brown’s node study method. This used a small axe to split the biscuit-sawn timber to contain the pruning scars to determine the depth of clearwood outside the pruned stubs and occlusion.

Some Karioi Ponderosa had been first pruned in 1943 which was 17 years before my evaluation, yet on some of those trees the clearwood sheath had not yet started. I came to the conclusion that rotations of at least 70 years were needed before significant amounts of clearwood would be produced. My report almost disappeared except I had given a copy to the Director of Economics Ron Williams and he was impressed.

The sequel was that the Wellington Conservancy had asked for head office approval to spend about a million pounds pruning and thinning Karioi forest. The Director of Management, Alan Familton, was highly sceptical but did not have any convincing evidence on which to decline the request. He discussed his misgivings with the Director of Economics and my report came up.

Alan Familton used the report to decline the request and asked Wellington Conservancy to provide alternative evidence. None was ever supplied. I felt rewarded – my first research effort had saved a greater sum than all the money I would ever earn in my entire career.

Scientific pruning

In 1963 before going overseas I was assigned to the Forest Research Institute to work with Bob Fenton. I was asked to look at the relation in pruned logs between the small end diameter, the size of the knotty core and the final log size log. (See the paper by Fenton, Sutton and Drewitt in the proceedings of the First Pruning and Thinning Symposium.)

What that research clearly showed was that the maximum volume of clearwood was obtained by keeping the knotty core as small as possible and the final log diameter as large as possible.Yes, the study was theoretical, but in 1963 there were few large pruned logs with small defect cores available for sawing. In 1965, after getting my forestry degree, I was posted to the Forest Research Institute and joined a new research group, the economics of silviculture branch, with specific responsibility for pruning and thinning.

It was not until the late 1960s that pruning became ‘scientific’, in other words based on measurement and economics. Then pruning was applied generally only to young radiata plantations. This meant pruning early, to restrict the size of the defect core, with heavy early thinning to a low final crop stocking to maximise the diameter of the butt log.

By the end of the 1960s or early 1970s two principles emerged from our plantation management research −

  • That the size and the quality of trees at harvest were determined by the decisions at the time of planting − site, species, genetics and spacing − and by stand management in the first few years such as thinning and pruning. This meant that by five or six years the quality of those trees had already been determined, even though the trees would not be harvested for another 20 to 25 years.
  • Log and tree returns at harvest time are determined not by log and tree costs at the time of early management decisions but by the price which exists on the day of harvest.

Export dependent

For radiata pruned sawlogs there are at least two decades between the time of early management decisions and that of the final harvest. In the early 1970s I was aware of these principles, and as New Zealand already had a greater area of plantations than we could expect to use locally, it was obvious that our forestry future depended on wood exports. The trees which we were tending in the early 1970s, and whose quality we could still influence, would be finally harvested around the year 2000.

I wanted to know what wood products could be in demand and at the highest prices around the year 2000. In 1972 I obtained a scholarship for a doctorate on this question. The key to my assessment of the year 2000 was the realisation that, although most overseas forest managers were largely unaware, the principles that we had found for our plantations were just as applicable to all of the world’s forests, especially plantations.

I researched all of the world’s major softwoods and came to the conclusion that our radiata clearwood was not only a substitute for old growth Ponderosa pine, which was probably the most valuable softwood in North America, but also that there were very few other tree species which could compete with our radiata. I independently confirmed what Stan Reid had been telling us decades before.

With the advantage of hindsight I should have expanded my study to cover hardwoods because these have continued to supply the global markets which I expected would have needed our clear radiata. However, there is a limit to what can be done on your own within three years and I was also limited by what information was available.

Convincing owners to prune

On my return to New Zealand in 1975 I gave hundreds of presentations summarising my supporting evidence and advocating timely pruning. My major concern was how to convince forest owners to prune when there was no established market for radiata pruned logs and none could exist until pruned logs became available for sawing or peeling in about 20 to 25 years’ time – a classic Catch 22 position.

My talks were generally well received but there were significant objections. Probably my most ardent critic was the then Director of the Commercial Division of the Forest Service, Bruce Webby. Bruce, at the conclusion of my Rotorua presentation, claimed that ‘plantation owners can prune as much as they like but sawmillers will never pay anything more for pruned logs.’ Of course, he could not have experienced or seen the sawn output of a well pruned log.

As for exports, Webby also claimed that nobody overseas will buy that ‘crap’ referring to long length radiata clears. With some notable exceptions, sawmillers seemed to have generally agreed with Webby − probably because sawmillers had sawn logs that were claimed to have been pruned but had been pruned so late that there had been little or no improvement in grade out-turn.

To enhance the quality and the volume of the butt log, timely early pruning with heavy early non- commercial thinning to a low final crop stocking has been advocated. However, this increases the management costs as well as reducing tree growth. Selective pruning, just pruning some of the final crop trees, is not practicable as experience and research has demonstrated that selected pruned trees tend to be quickly overtaken by their unpruned neighbours.

Tombleson in 2018 quotes estimates that, to compensate for the cost of pruning, as well as the volume loss per hectare as a result of pruning, pruned logs at felling should have premiums of at least $100 a cubic metre greater than unpruned logs. Current premiums for pruned logs are about half this estimate. Possibly for this reason, the two largest plantation investment companies in the central North Island have generally decided not to prune.

These investment companies have no doubt carried out studies on future markets as well as assessed other possible global sources of supply and concluded that there will be a limited profitable market prospect for pruned radiata clears. As no other country or species can grow clearwood, these companies must have good and strong evidence that our radiata clearwood will not find ready and profitable export markets.

Adding value

New Zealand is concerned about exporting low value unprocessed green and wet logs so a sure way of ensuring domestic processing is to prune in a timely fashion. Domestic processing and exporting just dry finished timber virtually eliminates the risk of sap stain. By concentrating on current log sale values, New Zealand could be seriously under-estimating the long-term benefits of pruning.

The current premiums for pruned logs are lower than most growers or investors expected and are probably less than the compounded cost of pruning and volume loss. However, the downstream added-value benefits of pruning have been generally ignored.

Because of the possibility of pruned logs becoming sap stained during sea transport, it is better to process pruned logs in this country. Tombleson estimates that the 12 plants in the central North Island process 1.226 million cubic metres of pruned logs a year, employ 1,575 staff and have an annual turnover of $734 million. These returns work out at $586 a cubic metre or $466,000 per process employee.

This is an added value multiplier of more than three or four times the return that growers receive from supplying the domestic and export log market for the best quality unpruned logs. The return to a processor of pruned logs, especially the return per employee, is not as good as this analysis suggests because processors need to buy the pruned logs in the first place. Even if there is a lower current harvest price than expected, the case for timely radiata pruning appears to be overwhelming, especially as it ensures we have our own unique special product.

Unique story

While on the theme of clearwood I am reminded of an incident which occurred when I was employed by Fletcher Forests. The company was exporting clear mouldings to the USA through a north American joint venture company. That company sent a senior manager to access the sustainability of future clearwood supplies.

Just the drive down from Auckland to Rotorua was enough to satisfy him that there would be few problems obtaining future supplies. As part of his New Zealand tour I took the company representative on my plantation history tour. At the end of the tour he commented ‘you claim that in the 1970s New Zealand was tending its plantations to supply us with radiata clears in the 1990s.’ I, of course, replied that we were. Then he completely blew my confidence away by saying ‘but you never told us so’. To this day we have largely not told our unique story to the world. As a marketing tool we should because it is a good and interesting story.

Long internodal or uninodal trees

It is now almost overlooked, but in our 1968 paper advocating heavy early thinning to the final crop stocking, Fenton and I included the recommendation that pruning selection be biased towards the tendency of the second log, the one above the butt log, to have long internodes. These logs could later be sawn for clear cuttings.


The head of the Forest Research Institute’s tree improvement section, Ib Thulin, appears to have been very much against uninodal or long internode trees. He maintained that uninodals were never straight and were never dominant.

How was it that an obvious uninodal was selected as a 26-year-old representative of un-thinned and unpruned radiata pine? The photograph above, published by the government printer in 1964, clearly shows a uninodal which is both straight and dominant. Since then there has been little selection for long internodes and uninodals, and most of the tree breeding effort has been to reduce internodal length and increase the number of branches. Tree breeders often maintain that their basis of selection has the support of the captains of industry.

Although long length clear radiata is required for mouldings and plywood, most of the clearwood users, such as furniture and joinery manufacturers, do not require long length clearwood. I am aware that the recovery of radiata short clear cuttings of 1.2 metres and longer is uneconomic at present. New Zealand and Chile have largely abandoned the process.

I contend, however, that we should be taking a long-term view. If this were 1900 there would be an abundance of high quality clears form the likes of kauri and rimu available for little more than the cost of felling and sawing. An advocate for clear radiata pine would never attract support in 1900 even though it was obvious to some that one day there would be almost no New Zealand indigenous trees available for sawing and peeling.

Recovery of clear cuttings is currently uneconomic but will this always be the case? In 20 to 30 years’ time most of the world’s large high quality trees will have been felled or be unavailable for exploitation. Although most of the world’s indigenous forests are claimed to be sustainably managed, I have serious doubts that most of these forests will have large trees capable of producing clearwood.

When clear, radiata pine is among the best softwoods in the world. In 20 to 30 years our clears from timely pruning and our clear cuttings from long internode and uninodal trees will be in great international demand, and prices for both will be higher than those today. Remember there will be almost no international competition.

Silvicultural research

I am also concerned about direction of some silvicultural research, especially the drive to increase average wood density and to advocate for higher final crop stockings. The push to increase average wood density has come from a desire to increase radiata’s structural wood properties, especially to increase the modulus of rupture or stiffness.

Compared with overseas plantations our radiata may have slightly lower average wood densities but our radiata is not as stiff as comparable plantation woods – wood such as that of the southern pines and Douglas- fir. But our radiata is not brittle when compared with comparable tree species. For its wood density radiata tends to have a higher modulus of elasticity or ease of bending compared with comparable plantation tree species.

We are constantly told that average wood density is an important measure of wood quality. If that is so we would expect that balsa wood, one of world’s lowest density woods, to be virtually unsaleable and Amazonian hardwoods, which have average dry wood densities of over 700 kilograms a cubic metre, to be in great demand.

In fact, the opposite is true. Balsa wood is in great demand and attracts high prices while dense Amazonian hardwoods are often unsaleable. Radiata wood has excellent finishing properties – the result of radiata latewood only having slightly higher wood densities than the earlywood. In addition, there is a gentle transition between the earlywood and latewood bands.

No competition

I just trust that the attempt to increase wood density is not at the expense of radiata’s excellent finishing properties. I am yet to be convinced of the need to produce a better structural timber, that is one with a greater modulus of rupture, from our radiata plantations. My analysis of the future global wood supply shows that there will probably be no shortage of structural timber unless the trend to build using wood results in a quantum increase in wood demand.

Compared to clears, structural sawn timber grades do not attract high prices. Anyway, even if a building requires mostly structural grade sawn timber, some finishing grade sawn timber will be required for interior fittings. There is no chance of New Zealand swamping the global clearwood market. We can never supply more than a few per cent of the global wood supply and our clears face almost no competition.

Chile may prune but, because of the demands of the pulp industry, it is locked into short rotations and high stocking levels. Most of major radiata growing areas of Australia generally do not prune. South Africa has a very small area of radiata plantations. Spain generally does not prune its radiata. Globally, no other plantation trees have the potential which our radiata has.

Increasing wood density or stiffness in no way qualifies our radiata as a unique special product − such a move makes us just another commodity producer. It may be to our advantage if we aimed to reduce radiata’s wood density as well as less difference between the densities of earlywood and latewood to improve radiata’s finishing properties. If wood users require a higher density wood then there are chemical and other treatments available which can achieve this. Perhaps there is a case for breeding two separate radiata types – one specialising in low density radiata clearwood to be pruned and the other in higher density and stiffer structural timber which will not be pruned.

Yield and returns

I am also not impressed with the attempt to maximise yield and returns. Harry Bunn, Bob Fenton and I attempted to do this in the late 1960s but to my knowledge, because it appeared to be so obvious, we never published our findings. With flat stumpages, that is with no price premiums for log size or log quality, it is possible to theoretically maximise yield and returns, but you introduce realistic premiums for log size and log quality and it is nearly impossible to maximise both volumes and financial returns. High stocking reduces average piece size as well as increases the yield of pulp wood which universally does not command high prices. In addition, when the stocking level is high and the average piece is small there will be a greater volume of slash left on felled areas. The day may come when the public object to minimally tended radiata stands, especially when they realise that this treatment could be depriving the nation of increased employment and overseas earnings opportunities.

Wood wasp

Most are no longer aware that the driving force behind the original John Ure radiata regime was New Zealand’s experience with the sirex wood wasp. Although up to 90 per cent of unthinned stems could be killed by the wood wasp, some trees survived. I can just remember seeing sirex affected stands – they looked terrible. They gave the appearance that every tree had been killed.

No wonder overseas visitors as well as local critics were quick to condemn the nation’s concentration on radiata.

All the talk in the 1940s and 1950s was the need to thin radiata to a final crop stocking below the mortality line. Experience had shown that for mature stands this was about 80 stems an acre or 200 per hectare. Because of the introduction of parasites, sirex is no longer a problem, but with high final crop stockings we run the risk of some unknown destructive insect or disease being introduced causing havoc in highly stocked, and ever-increasing stressful conditions as stands age.

A New Forest Service?

With the philosophy that plantation forestry was now a mature industry and that all decisions, especially financial, could be better done by the private sector, the Labour government of the second half of the 1980s broke up the Forest Service. State plantation forests were sold, other functions dispersed and forest research became a crown owned research institute, now called Scion. Remnants of the Forest Service were absorbed into the Department of Primary Industries. Largely lost in the breakup was the planning function of the Forest Service .This provided politicians with independent advice on the forestry sector.

However, the current Labour coalition government has re-established part of the former Forest Service – Te Uru Rakau. I trust that planning is one of the responsibilities of this new government department. There is an urgent need to address the wood supply problems that will arise from the nation’s grossly uneven past plantings. The 1990s saw a great new planting effort which was followed by almost two decades in which there was more plantation conversions, especially to dairy farming, than new plantation establishment.

New Zealand could see an export bonanza in the 2020s followed by a severe wood export shortage in the 2030s. Only an independent agency can solve this and other problems and advise the government of possible courses of action.

Final comment

New Zealand is fortunate to have introduced radiata pine in the latter half of 1800s. The plantation tree proved ideal for our climate and our soils. Experience and research over the last 150 years have given the tree species advantages that should be the envy of most other countries.

With stand management we can grow large diameter trees in 25 to 30 years. With timely pruning and thinning, combined with tree improvement concentrating on long internodes, we can produce clearwood that is the equal of best softwoods in the world. As other counties either cannot grow radiata or choose not to manage their radiata for maximum clearwood production, New Zealand is in a unique position.

Clearwood is our USP – uniquely special product.

Further reading

Brown G.S. (Comp), Bunn, E.H.(Ed) 1963: Pruning and Thinning Practice in New Zealand FRI Symposium No 3 New Zealand Forest Research Institute.

Fenton R.T. Sutton W.R.J. (1968): Silvicultural Proposals for Radiata Pine on High Quality Sites.
New Zealand Journal of Forestry 13 (2): 220-8

Sutton W.R.J. (1975): An Evaluation of New Zealand’s Forestry Export Potential. D. Phil thesis Oxford University.

Tombleson J. (2018) Pruned log supply from the Central North Island and disrupter influences on wood processing. NZ Journal of Forestry 62(4): 5-9.

Ure J. (1949) The Natural Regeneration of Pinus radiata on Kaingaroa Forrest. NZ Journal of Forestry 6 (1): 182- 192.

One post

Post from Shem & Jen Kerr on October 11, 2019 at 12:44PM

I attended a loppers ladders pruning saws Bunn-Barr clinic. There was lots of enthusiasm. More of a religious conversion event than science. Then I went to the field day at Inglewood Timber Processors. Totally unpruned trees were cut into boards cambian to cambian which were then kiln dried before being trucked to the factory where the knots were sawn out and bagged for firewood. The remaining timber was finger-jointed and exported to USA as balustrade; architrave; door blanks; etc. This is with 18 – 23% return on investment, as against 7 – 9% return for pruned trees. That was all last century,- has anything changed? Well, further disruption to the 27 year clear-pruned rotation: short rotation forestry at close spacing, - where pruning makes even less sense with radiata pine; though it might make sense with short rotation eucalypts. Is there a game changer or two that could advantage the concept of clear pruning?

Please can we have a recalculation of the costs/benefits of clear-pruning done by robots; or pruning machines. I know NZ likes to think that it's forestry is leading edge, but I can't find any evidence: maybe it's all top secret. There are some overseas examples: Pruning trees with the Clouston Tree Pruner (video); and article ; " A Pruning Robot With a Power-Saving Chainsaw Drive," by Yasuhiko Ishigure, Katsuyuki Hirai, and Haruhisa Kawasaki. 

Advaligno Patas 2018/09 - maschinelle Hochastung - mechanical delimbing - élagage – prototype

I can see some issues. What do you think?





Blackwoods - selecting the best trees

Ian Brown's Blog
Thursday, July 04, 2019

In theory, there are two simple steps in tree improvement. Select a provenance that matches your site, and from it identify trees with superior traits to breed from. However in practice, it isn't quite that simple.

For radiata pine, provenance selection offers limited choices. There are just three locations to choose from on the Central Coast of California. (Most of our original land race appears to have been sourced from a scruffy patch of coastal forest at Ano Nuevo, near Santa Cruz. Obviously, appearances can be deceptive.)

However like most of the other big conifers that like to assemble themselves in monocultures on their home territory, pines tend to breed true, the kids generally resembling their parents. Although this has made life easier for the tree breeders, the present generation of quality pines that we have still needed many decades of world class research.

In contrast, with blackwoods we have an abundance of provenances to choose from, each of them adapted to its location. But for potential tree breeders there is a problem with individual tree selection. Blackwoods are at home in mixed communities, where survival demands flexible growth responses when jostling for space among some mean competitors, and this has shifted the balance between nature and nurture.
Like human societies, the best behaved blackwood parents often produce wayward offspring, easily led astray by environmental influences. On the other hand, the parent trees can deliver some unfortunate traits to their kids. You might consult the opening lines in Philip Larkin's poem, a favourite among small children, "This be the verse".

Provenance selection.

The natural range of blackwood is remarkable, even among Australian species, extending from the cool damp forests in Tasmania to the warm tropics in Queensland. So which provenance is best suited to New Zealand?

Blackwood genetics.

In 1993 J. Playford and colleagues published a genetic study, based on allozyme variation. They tested 27 blackwood provenances, covering the natural range. I will summarise some points of interest.

  • there is considerable genetic variation between provenances, linked to latitude of origin.
  • there is an even higher degree of variation among trees within each provenance.
  • there is a major genetic disjunction among populations, corresponding with the Hunter River district in NSW. Blackwoods north of that zone are genetically distinct from those further south, and may be in the process of separation from them further, to form a distinct species. Blackwoods are a temperate species, and in the north they find themselves outside their comfort zone. They are more at home there on the hills and ranges, where they form isolated communities. Geographical separation is one of the factors linked to speciation.
  • further south, there are some interesting anomalies between populations that are geographically separate but genetically linked. You might expect that the provenances in NE and NW Tasmania, that perform equally well in trials and which are close geographically, would have a strong genetic linkage. In fact each of them has a closer genetic linkage to mainland populations on the other side of the Bass Straight, NW Tasmania to the Otways, and NE Tasmania to South Australia and Victoria. It is as if the Bass Straight, a formidable stretch of water, did not exist. Of course until recently, in geological time, it did not. The former Bassian Plain, which linked Tasmania to the mainland during the recent ice age, with woodland on the western flank and dry steppe to the east, would have allowed a flow-path for gene transfer until il was flooded by rising seas 14000 years ago, in the process isolating mainland Australia from civilisation in the south.
  • the study tells us nothing about the specific attributes that are of interest to us, i.e. vigour and form. Some growth traits can be very localised. For example, we could take phyllode structure. This has an association with latitude of origin. In the northern populations the phyllodes are longer and thinner than those in the south. However phyllode morphology has a stronger genetic linkage to local influences, in particular the distance from the coast. Among inland populations the phyllodes are long and thin, tough and waxy, sacrificing photosynthetic output for survival in a hot dry climate. Among coastal blackwoods where soils and climate are more favourable, the challenge for survival is competition for light. Here the phyllodes are large and fleshy, giving them a high photosynthetic output, and as a consequence a greater growth potential.

The genetic evidence from studies of this type may be interesting, but from the perspective of tree growers it is of limited value. To obtain the information we need, we have to rely on field trials.

Provenance trials

Offshore trials

Approximately 60 provenance trials have been run internationally over many years. From these we might expect an abundance of useful information. Gordon Bradbury in Tasmania has looked at them critically and has found major flaws in most of them:

  • provenance numbers have often been limited, and focussed on local sources.
  • the trial sites have often been of poor quality, dry and exposed, and with impoverished soils. I have seen one or two of them, and would not choose to plant blackwoods there.
  • poor management. This includes lack of weed and predator control.
  • lack of documentation, and few published results.

A common theme is that local provenances perform best, but there are exceptions. In trials in SW Tasmania and in SW Victoria, trees from NW Tasmania outperformed the local provenance. In NE Victoria, NSW, and Queensland, the local provenances scored well.

In trials In South Africa, where blackwoods have been grown from the 19th century, local selections outperformed those from offshore.

The data from China are interesting. The Chinese have been trialling blackood from the 1990s in extensive experimental plantations in the Guangdong province, in the south east. They are keen to establish blackwood plantations because it matches the traditional timber used in their most valued furniture. They have tested 35 provenances, and early data have shown the best results from Queensland. (Perhaps this should not be surprising. Anyone who has spent time in Hong Kong will know that the climate in SE China matches Queensland more closely than cool Tasmania.)

In a trial site in Lanco, Chile, the Tasmanian provenances performed best. The NE Tasmanian provenance headed off NW Tasmania.

Meunna Trial

Of the Australian trials, The one that I think is most useful to us was set up in Meunna, in NW Tasmania in 1988 and 1989. The site has good quality soils, and high rainfall, so it matches the sites that we would use. It tested 56 Tasmanian families, and 7 from the mainland. The trial was carefully planned and managed. The trees were protected by tubes from predation by marsupials , and were tested in plots with and without a eucalypt nurse.

Gordon Bradbury assessed the outcome at age 17 and 18. The best performing provenance was from NE Tasmania (Scottsdale), followed by NW Tasmania. SE Tasmania lagged behind. The provenances differed in volume, but not in form, which was consistently bad. Gordon made some interesting observations on wood colour, which I will refer to later.

New Zealand Trials

There have been a few limited trials carried out in the past, and two more substantial trials which I will describe.

1984 trial.

This was established by FRI on 10 locations, 3 in the North Island and 7 in the South, ranging from Tairua in the Coromandel to Longwood in Southland. Of the 31 seedlots that were tested, there were 9 from Australia (6 Tasmania, 2 Victoria, and one NSW). 14 were from South Africa, and the rest were from New Zealand and Chile.

The North Island trial sites were assessed at age 8 in 1992. The best provenances were Smithton (NW Tasmania), Scottsdale (NE Tasmania), Jeeralang (Victoria), and Waipoua Northland. The Waipoua trees had been sourced from a Smithton seedlot. The South African and Chilean provenances performed poorly. The Jeeralang trees had good form but lesser diameter. Dudley Franklin examined the trees in the south for frost tolerance, and found that the Tasmanian provenances were most resistant.

A further detailed assessment was carried out on two of the North Island sites in 2002, at age 18. The beat provenances were Scottsdale ( marginally on top), Smithton, and Waipoua.

2004 trial

Ian Nicholas and colleagues from FRI established two trial sites, one on my property at Pirongia in the Waikato, and the other in Westland. They contained 65 seedlots from 13 districts. 12 of the districts were in Australia and one in New Zealand. Ian visited the Westland site several years later, and he told me that it had been overwhelmed by weeds, and was unlikely to provide any useful data, so it appears to have been abandoned. This leaves us with the Pirongia trial.

The Pirongia trial is on what I would regard as a typical good North Island site for blackwood. It is located on the lower slopes of Mt Pirongia, the soil is volcanic in origin , free draining, and of moderate fertility, gently sloping and reasonably sheltered from the prevailing wind. Rainfall is high, at over 2000 mm per year.
The seedlings were planted in compartments, each representing a district, and each contained 8 copies of 5 seedlots. There were 4 replicates of each, giving a total of 2080 trees.

Ian Nicholas made an early assessment, at which time the NE Tasmania provenance was heading the pack.

At age 7, Toby Stovold and colleagues made a detailed assessment, measuring height and diameter, and grading form for each tree on a nine point scale. The results were as follows, the best trees at the top.

  1. North Inland Tasmania
  2. North Eastern Tasmania
  3. New Zealand. (seed origin probably NW Tasmania)
  4. North West Tasmania
  5. North Tasmania
  6. Otways Victoria
  7. South Tasmania.
  8. Queensland and Chile
  9. Gippsland Victoria
  10. South West Victoria
  11. NSW high
  12. NSW
  13. Central Victoria

The message for us is obvious. The top five provenances are all in Northern Tasmania. Interestingly, our traditional seed source, NW Tasmania, came fourth on the list.

When the trees were at age 10, I could not resist the temptation to carry out some crude measurements of my own, that could be described as quick and dirty. What follows is not science, and I would suggest that anyone with a background in forest science should read no further.

I took the perspective of a guy with a chainsaw heading into a neglected woodlot for some selective culling. I made a subjective assessment of each tree, scoring them on a three point scale:

0 - a hopeless case. You could have done nothing with a tree like this. Pass me the chainsaw.

1 - pretty average. You might have made something decent with it, but it would have needed serious work.

2 - definitely a keeper. With some light form pruning this could have been a classy tree.

Well, you cannot complain you were not warned.

Bearing in mind that I perpetrated this raid on science a few years down the track, the pecking order followed quite closely the previous, and more legitimate 7 year assessment. Again, he top five provenances were all from Northern Tasmania. Top performer was NE Tasmania. I gave a higher ranking for NW Tasmania, now in second place, and a slightly higher place for Gippsland. Best performers in NE Tasmania were Scottsdale ( this name seems to crop up), Fingal, and Swansea, but the numbers are too small to mean much.

To be honest, when I walk through the plots from NE and NW Tasmania and simply glance at them they look very similar. I would be happy to plant either of them. At age 15 all the Northern Tasmanian groups now tower over the others. Considering that they also have lower mortality, it really is no contest.
Some of the provenances have distinctive features. At least two have a flowering time that is different from the rest, suggesting that they may be on the way to forming separate subspecies. One of the 65 provenances was resistant to attack by psyllids, which have been incriminated as a cause of malformation in blackwood. In theory it should have had better form than the others, but in fact it was very branchy, and subsequently had high mortality.

In compliance with the protocol the trees have not been thinned or pruned, so are now showing significant mortality. So the 7 year data will be definitive.

In summary

  • based on Tasmanian and New Zealand trials, the best source for blackwoods for New Zealand is Northern Tasmania.
  • several trials suggest that provenances in NE Tasmania might head off NW Tasmania, but any differences between them are likely to be minor.
  • we can be confident with our traditional sources, around Smithton in NW Tasmania. However someone might like to try some from the NE (perhaps Scottsdale)
  • on the mainland, sources in Southern Victoria (Otways, Gippsland) might be considered, but why bother when Northern Tasmania is better?
  • forget about Northern Victoria, South Australia, NSW, Queensland, and South Africa.

Individual Tree Selection

Within any woodlot or natural forest of blackwoods you can find occasional "plus trees" of superior form and vigour. These are obvious targets for selection for propagation or for setting up a seed orchard. If it works for pines, why not for blackwoods? The answer is that pines tend to breed true, but a mix of anecdote and science suggests that blackwoods do not.

For example, back in 1957 Ib Thulin from FRI went to Smithton in NW Tasmania, and selected from the natural forests 10 trees of superior growth and form, and collected seeds from them. He planted seedlings grown from them on several North Island sites. They did not meet expectations. In fact their performance was average, and no better than unselected seedlings.

There is clearly an environmental effect, but how strong is it? An obvious approach would be to eliminate the genetic influence by taking clones from selected plus trees, and compare them with unselected seedlings. So, what do the clonal studies tell us?

It is surprising, but as far as I can determine, they have not been done, or at least have not been published. Admittedly it is not easy to clone blackwoods. I know, I have tried it. Unless you have access to a tissue culture lab, you have to take root cuttings, and it requires specialised nursery techniques.

But there is a gap in our understanding of blackwood genetics that should be closed before making assumptions derived from different species, and filling seed orchards with trees that might be no better than average. We have some limited experience in New Zealand with blackwood clones, and that is not reassuring..

In 1998 Ian Nicholas and Ian Barton took root cuttings from74 superior trees in the Hunua forest near Auckland. 35 were successfully propagated, and they were planted out north of Auckland. The objective was to establish an orchard of superior trees for later propagation. This was abandoned when it was found that the trees showed wide variation in form and vigour, and had no resemblance to their parents.

In 1997 I planted 90 blackwood clones on my property at Pirongia. They had been taken from a single tree selected for superior form and vigour, and which had high quality colour in core samples. They were evenly spaced, and interplanted with random seedlings. None of the trees were pruned or thinned.

At five years, the clones showed wide variation in form and vigour, and seemed no better than the control seedlings. I introduced Ian Nicholas to the trees, and Ian, Ham Gifford and I took some measurements. We chose at random 32 clones and 40 control trees, and measured their height and diameter. Form was assessed using a nine point scale.

The data gave some surprising figures. Average values were as follows:

  DBH (mm) Height (m) Bole break (m) Form (1-9)
Clones 104.69 6.17 2.27 4.47
Controls 100.49 5.93 2.83 4.75

In summary, there was very little difference between the two groups, the clones showing slightly more vigour. On the other hand, they had slightly poorer form.

Even more surprising, when the Standard Deviation (which measures the range of variation), was calculated, this proved to be less for the controls than the clones for all attributes:


DBH 38 - 175 mm Height 3.3 - 8.6 metres
Bole break 0.5 - 5.2 metres
Form 2-7

If we put all this together, and bearing in mind the obvious limitations of the two clonal trials, I think we should have some reservations about the heritability of vigour and form in blackwood. The non-genetic influence seems overwhelming.

Within a population of blackwoods there are likely to be a few individuals with a better genetic endowment for vigour than the others. However they would be difficult to identify. To test this properly it would require more robust trials, using different clones, and across several sites. They would also need to be tested over several generations. I doubt that this would be justified:

  • apart from the cost and time required, any genetic gains are likely to be modest, and limited to vigour, rather than form.
  • any benefit that might be achieved would be minor compared with the gains that can be made by good silviculture. We know that with seedlings from a good provenance and grown on a suitable site, and with proper management we can consistently produce high quality trees with a rotation of 35 to 40 years.


Vigour in blackwood depends on the provision of adequate light to the growing crown. The key to this is early thinning. A delay in thinning , even by a few years, forces the crowns to compete. This leads to slow diameter growth, and a long rotation.


Malformation in blackwood can be reduced, although not eliminated, by interplanting with a nurse or trainer species. But there is a cost: reduced diameter, slow growth, and a possible adverse effect on wood colour. However you can eliminate malformation and produce consistently straight trees, even when open grown, if they are regularly form pruned.

Malformation in unpruned blackwoods is inescapable. It can result from any random influence that damages the leading shoot tip, such as attack by psyllids. However, there is a deeper influence.
Malformation is embedded in the growth habit of blackwoods, in which periods of extension growth are repeatedly terminated by abortion of the shoot tips and their subsequent replacement. This serves the interests of the tree, allowing it to develop and expand its branches when exposed to light. There is no way we could breed this out of the tree without converting blackwood into a different species.

Does that mean we should abandon hope of genetic gain?

Not necessarily. There is a third feature that has, with a few exceptions , been surprisingly neglected in efforts to breed improved blackwoods. That is the quality of its timber. After all, that is what makes blackwood so distinctive, and ensures its place among the great decorative timbers.
It could be even better if we could resolve a problem encountered by the end users, and that is the variability in colour and density of the timber. The question is, to what extent are colour and density genetically determined?


Environmental influence

In 1975 C.M. Harrison , in South Africa, published a study based on 196 trees, which examined the relationship of colour in blackwood to site. He concluded that there is a linkage, and that the best colour is associated with good soils, the number of rain days during the growing season, and sites that are cold and dry in winter. This study has been frequently referenced since then, but if true in South Africa, does it also apply here?.

More recently, Ian Nicholas in New Zealand, and Gordon Bradbury in Tasmania have independently studied a possible linkage, and both have found no evidence of a relationship between colour and either soil or rainfall.

For example, in a study in NW Tasmania where trees from the same seedlots and established on the same protocol, had been planted at Meunna (wet), and at Virginstow (dry) , there was no difference in colour between them.
Ian Nicholas examined thinnings from 18 year old trees planted on 6 North Island sites, and found no significant difference in colour between them.

If colour is not linked to site, what about a linkage to growth rate? It has been argued that fast growing plantation blackwoods could have inferior colour than slower growing trees in natural forests. Again, both Ian and Gordon have independently examined this, and have come to the same conclusion: there is no relationship between colour and growth rate in blackwood. We can therefore confidently employ silvicultural systems that support early crop rotation.

In a separate study, Ian Nicholas examined wood samples from New Zealand and Tasmania, and found no significant difference in colour between them.

Gordon Bradbury made an unexpected observation in the Meunna trial. The trees that had been interplanted with a nurse species (E. globulus) had not only smaller diameter, as you would expect, but they also had a paler and less interesting colour than those that had been open planted. I have not seen this reported previously, but if could be confirmed on other sites it would have obvious implications.

There have been anecdotal suggestions that the colour becomes darker as the trees age. This does not appear to have been tested in formal studies, but if it were confirmed, it would hardly justify a delay in milling.

Provenance studies have shown that colour can vary between provenances, and have confirmed that there is wide variation between trees in the same provenance. Colour can vary between locations within the same tree, and tends to be darker in tension wood.

Genetic influence.

The limited data that we have suggests that colour in blackwood is more strongly linked to genes than environment. I am aware that anecdotal evidence is not respectable, but anyone who has thinned out a large number of blackwoods will have been impressed by the wide range of colour in trees that are a few metres apart. It is hard to imagine that subtle differences in what appears very uniform soil could have that effect.

The trial data on colour that I have referred to also suggests that environmental influences are not significant, which would by default incriminate genetics as the main influence. The obvious way to sort this out would be through clonal studies that compare clones with random seedlings. As you might expect, these have not been done, or as far as I know published.

With some apprehension, I will refer to a small test, which could be described as a trial run, on my blackwood clones. I cut a large branch off 24 of the clones, and 24 of the seedlings, cut discs, and lined them up. All the branches had heartwood. From previous observations on thinnings , and a published report on A. Koa I am confident that the branch colour matches stem colour.

As expected, colour among the seedlings showed wide variation. Most were in the middle range. Some were pale and unexciting, and one or two were darker and more interesting. In contrast, the colour in the clones was darker. More significantly, they showed a high degree of uniformity.
This can hardly be described as science, but suggests a genetic link to colour that would be worth a formal study. Ian Nicholas and I had planned to set this up on the clones at Pirongia , and we had some funds approved from AMIGO, but we were overtaken by events. This could be activated, and I think would be worth doing.

A full study would need several different clones, tested against seedlings, on different sites. This would provide a definitive answer, and after removing the

control seedlngs could leave a valuable resource for milling, or breeding. Of course that would require you to choose your colour.

Choosing your colour.

Not all blackood timbers are of equal quality. The best of them have a rich colour and texture and could be mistaken for mahogany. Some have attractive reddish elements, others dark, more like black walnut. And there are some logs that are pale and uninteresting. Faced with this multicultural assemblage the miller has two options: to keep an inventory large enough to allow colour matching. Or what is usually done: to make the best of it, lump them together, and present the variations to the customer as a special feature of blackwood. However I am told that if given a choice they would welcome a uniform product , and pay a premium for it.
If you decide to go clonal, what colour should you choose? There is no point in asking the architects. They follow trends, which is currently for a deathly white. You can be sure that whatever is trendy today will be out of fashion in a few years. Don't ask the scientists. They are likely to drag a colorimeter into a furniture store. Ask the customer, who of course is always right.

Also ask the Chinese, who are likely to our main customers for blackwood timber. I am assured they would welcome a regular supply of blackwood timber. I have looked about in one or two furniture stores in China. They have some classy furniture, and the wood looks very much like rain forest mahogany. It probably is rain forest mahogany. However it could easily be replaced by certain grades of blackwood. In the Shanghai Museum there is some fine furniture, simple and modern in style and also resembling mahogany, that dates from the Ming Dynasty. My guess is that something in that colour range would be a safe bet. Or you might aim for a palette with two or three different options.


I will summarise the evidence from studies in New Zealand and Tasmania.

Blackwood has a wide range in density. At the lower level it should be sufficient to protect the furniture from a sustained attack by the toddler armed with her toy hammer. However with an increasing interest in blackwood for flooring, higher density values could be important. And if we could provide blackwood with uniform density, it would be welcomed by the furniture makers, who find that mixing boards with different densities can be a problem.

The evidence suggests a strong genetic influence on density. There is a weaker environmental effect. Whatever that might be, it does not appear to be linked to rainfall.

Fast growth does not compromise density. In fact, in a New Zealand study, faster growing blackwoods had slightly higher density. This links blackwood with the ring-porous species ( in ring porous species, such as oak, fast growth is linked to high density. In diffuse porous species, such as poplar, the opposite is true).

Conveniently, in blackwood there is some evidence of a possible linkage between higher density, and darker and reddish timber. If true, that might provide an opportunity to kill two birds with one stone.


Both growth and form in blackwoods are powerfully influenced by environmental factors.

Some trees within a provenance are likely to be better endowed than others in vigour, although this does not appear to apply to form. However they would be difficult to identify. This would need several generations of testing, and would be likely to produce only modest gains. These would be dwarfed by the benefit of good silvicultural practice.

On the other hand, the wood properties in blackwood, in particular colour, appear to have a strong genetic link. I think this should be the priority in any genetic improvement program, and could offer opportunities in a niche market.


By now, the reader will know that I have pillaged ideas and data from two leading researchers, the late Ian Nicholas in New Zealand, and Dr. Gordon Bradbury in Tasmania.

Over many years I have exchanged ideas with Ian, argued, collaborated , and learnt from him. Sorely missed.

Gordon has done excellent blackwood research in Tasmania. His website, is provocative and well informed on a range of topics, and certainly worth a visit.

Disclaimer: Personal views expressed in this blog are those of the writers and do not necessarily represent those of the NZ Farm Forestry Association.

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