Farm Forestry New Zealand

Will Hull’s contribution to radiata pine plantation management

Wink Sutton, New Zealand Tree Grower November 2012.

To fully appreciate Will Hull’s contribution we need to look at the evolution of New Zealand silviculture. When plantation forestry began in the 1890s there was limited local experience and very little universal experience or guidance on how plantations should be managed. New Zealand was greatly influenced by European, especially German, thinking.

The guiding principle was that plantation management should, where possible, replicate nature − very close initial spacing of 7,000 to 10,000 trees a hectare and the minimum of tending. If the stand was left to mature, it should produce quality trees similar to that found in the natural forest. Management was particularly averse to pruning.

Mathews in his 1905 book Tree-Culture in New Zealand was hostile to all pruning, except possibly the early removal of multiple leaders. Typical of his hostility is Mathews’ comment ‘The pernicious practice of mutilating trees by amputating live limbs close to the stem is pregnant with evil results.’ We can only speculate how Mathews would react if he was still around?

Untended trees

The early plantations, including those established during the depression of the early 1930s, were not tended. There was simply no money and no agreement on how stands should be treated. Later there was a growing realisation that young plantations should be pruned to produce knot-free wood. But the government did very little planting of radiata pine from the mid 1930s to the early 1950s and so pruning was confined to other slower growing species – Douglas fir, ponderosa pine and Pinus nigra.

From the early 1960s production forestry research was given increased emphasis and increased funding. It seemed obvious that if we wanted knot-free radiata timber or veneer we should prune, especially as radiata could grow quickly to a large diameter. As some radiata pine trees have long internodes we knew that knot-free radiata timber had excellent finishing properties.

We also knew from splitting pruned nodes that clearwood was produced, but we lacked proof from actual sawing trials that artificial pruning resulted in high quality long length clears. To have been mature in the mid 1960s the trees would have to have been pruned in the early 1940s or before. The problem was that there were no mature pruned logs available in any of the government or company plantations. Only the government forests had any pruning of significance with none of this on radiata and almost none was before the 1950. The exception were the radiata pine trees of Will Hull.

Why Will Hull pruned radiata

At the 2011 NZFFA AGM breakfast, by chance I happened to be seated next to a Bob Williams. Bob knew a lot about the Hull trees and told me how and why Will Hull came to prune his trees. I found out later that Bob had married Will Hull’s daughter.

Will had fought in World War I. On his return to New Zealand he worked for a time as a bushman felling large indigenous logs in the central North Island, logs that produced mostly clear boards. Will was aware that unpruned radiata produced almost no clearwood and no long length clears.

Later he owned a farm Waierua at Whareama near Tinui. In 1928 he planted a strip of radiata a few rows wide at a spacing of about 1.8 metres. Will carried a hand axe with which he regularly and progressively pruned the radiata up to an average height of 14 metres. For the higher pruning lifts he used a ladder.

At age 20 years the stand was thinned. In 1963, when the stand was 35 years old, 12 trees were extracted with an average diameter at breast height of 61 cm, ranging from 41 to 70 cm, and an average height of 34 metres. The logs were sent to Forest Research Institute in Rotorua for sawing.

Was this the first?

This was the first sawing of early pruned radiata which had been left to attain a large diameter. At last there was proof that timely radiata pruning did result in the production of long clears. There was always a fear that occlusion over the pruned radiata branch stubs could have resulted in blemished clears.

Without the availability of the mature Hull trees we would have to wait another five years to 1968 before the first of the state forest pruned radiata trees were available for sawing. Those trees were only 26 years old.

Pruning is now common but its early adoption owes much to the innovative early thinking of Will Hull. What contributions will farm foresters make to plantation management in the future?

Postscript

The above was written in May 2011. I had forgotten that the state forests had one pruned stand. This was compartment 1045 Kaingaroa Forest, planted in 1920 at 1.8 by 1.8 metres. It was first pruned at age 10 when about 13.5 metres high, to two metres. It was second pruned by a saw mounted at the end of a pole, at age 15 to six metres.

The stand was twice thinned, first at age 15, the same time as the pruning, to 880 stems per hectare and then to 200 stems per hectare at age 31 when the height was about 41 metres. The stand was felled at age 42 when the trees were about 47 metres in height. The pruned logs, with a mean diameter at breast height 64 cm, were sawn at the Waipa State sawmill in 1962.

For comparison in the same study, similar sized logs, unpruned but Sirex thinned, were harvested from Compartment 1061 and sawn. Even though the pruning was late by current standards the improvement in grade out-turn was impressive.

Pruned logs had yields of 7.5 per cent clears, 42 per cent factory or clear cuttings grade and 48 per cent box when sawn to 25 mm boards. Similar yields for the same sized unpruned butt logs were − 0.6 per cent clears, 21 per cent factory grade and 60 per cent box. A technician in the study reported that the Waipa sawmill staff were excited because they had never before experienced such high quality wood.

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