Eucalypts: Trees of the Future?
Throughout the country, but especially in Southland and the Bay of Plenty, cohorts of young gum trees are parading their bluish leaves across the hills. A century ago, these trees were considered the answer to our dwindling supplies of native timber, and in state plantations they far outnumbered radiata pines. But they suffered a reversal of fortune, and are only now making a modest comeback in our forests.
Mention the word “eucalyptus” and most New Zealanders will think of “those Australian trees with the pungent leaves.” And they’ll be right, of course. Gum trees are as quintessentially Australian as “Waltzing Matilda” and koalas. Yet they have been part of the New Zealand landscape since the days of the first European settlers—and, during epochs when the climate was suitable, for thousands of years earlier than that.
To say the gum tree is Australia’s greatest gift to the world would be no exaggeration. In drier areas, such as California and South Africa, eucalypts have become so entrenched as both amenity and forestry trees it is hard to believe they are not natives. Many millions of hectares of eucalyptus forest have also been planted in Brazil, China, India and Argentina. In fact, eucalypts are the most widely planted hardwood trees in the world.
Not everyone is pleased with the gift. South Africans, regretting the extent to which eucalypts have come to dominate the rural skyline, are now chopping them down at a rapid rate. As long as a hundred years ago, a Californian writer made his feelings on the matter clear when he wrote:
There is a craze all over the state about the eucalyptus or Australian blue gum tree . . . Eucalyptus will frighten away fevers and murder malaria. Its leaves cure asthma. Its roots knock out ague as cold as jelly. Its bark improves that of a dog. A dead body buried in a coffin made from the wood of the blue gum will enjoy immunity from the exploring mole and the penetrating worm . . . [T]his absurd vegetable is now growing all over the state. One cannot get out of its sight . . . It defaces every landscape with blotches of blue and embitters every breeze with suggestions of an old woman’s medicine chest. Let us have no more of it.
Such harangues aside, why have eucalypts proved so popular? Chiefly because they can establish and grow rapidly, even in poor soils and arid climates. And not just in the dry. Such is the range of species (estimated to number 800) that there is at least one to suit almost any situation. Some thrive in the desolate outback (coolibah, black box), others in the wet tropics (flooded gum), in swamps (swamp gum) or on exposed mountain summits (snow gum).
Although in New Zealand eucalypt timber is only beginning to be rediscovered, it has been a staple of the Australian building industry for centuries. Wood colour ranges from chocolate brown (carbeen) through oxblood (jarrah) to white (Camden woollybutt), with everything in between, and the strength, hardness and density of some species are extraordinary. Take an axe to a block of tuart, one of the hard and heavy species from Western Australia, and the blows will bounce off as if you are hitting steel. In fact, wood from heavier species, such as red ironbark, is denser than water and will therefore not float. (Radiata pine is about a third as dense as red ironbark.)
Some species yield timber that is highly rot-resistant and ground durable. Its water content is so low it will not conduct electricity, and is therefore useful in electric fencing.
There is more to eucalypts than timber, however. Useful oils and solvents can be distilled from their leaves, and kino (an astringent gum used in medicine and tanning) from their bark. Eucalypts are widely considered the most efficient producers of high-quality woody biomass for fibre (an ingredient of high-quality paper) and energy (when burned as firewood). Many types flower profusely, and are a rich source of honey. Flowers and foliage from certain species are popular with florists, and, being fast growers, eucalypts make good shelter belts.
Some species reach a tremendous height. The tallest is mountain ash (Eucalyptus regnans), a native of Victoria and Tasmania. This species is said to attain a height of 100 m, and there are claims that an 1870s specimen, known as the Ferguson tree, towered 152 m high, and that many others of the time were only 10 to 20 m shorter. The tallest tree in the world at present is thought to be a 112 m coastal redwood in California, but eucalypts are the world’s loftiest hardwoods.
A mountain ash holds the height record in New Zealand, too, eclipsing any known kauri or kahikatea and even the tallest of the magnificent redwoods growing in Rotorua. The tree in question was planted around 1870 in Waitati, near Dunedin, and measures 70 m (see New Zealand Geographic, Issue 3).
Several other Eucalyptus species attain heights in the 70–90 m range. And they are not just skinny poles, either. Trunk diameters of 3 m are not uncommon—a decent girth by any standard.
The trees themselves are perplexing. Although the leaves on young trees may differ substantially between species, once the trees reach maturity their leaves become almost indistinguishable. Adolescent trees may bear several types of quite different foliage. The leaves of young white stringybarks, for example, are veined and hairy, while those of sugar gums are almost circular in youth and elongate with age until they assume the long taper so characteristic of eucalypts. The leaves of white peppermint, narrow in infancy, are as slender as snakes on the adult tree.
Given the size of the trees, the leaves are not that abundant in many species, being borne as clumps on the ends of spindly branches. Eucalypts are not great shade trees, and old specimens have a reputation for dropping branches.
Whereas most trees shed their leaves, many eucalypts also shed their bark. It often hangs in untidy sheets or strips from the trunk and lower limbs. In other specimens the bark may be as smooth and white as shark skin, dark and knobbly like that of an oak, platy and flaky like that of an old kauri (but more colourful), or stringier than the fibres on a coconut.
Many species bear rata-like blooms that give off a warm aroma of honey and range in colour from white and cream to yellow, greenish-yellow, pink, orange and red. (Indeed, eucalypts belong to the same family as our rata and tea tree.)
There is a great variety of form among gums, some species being just shrubs, some great sprawling trees, and others pencil-straight forest giants. Identifying them all is a considerable challenge—a theme exploited in Australian writer Murray Bail’s award-winning novel Eucalyptus.
Long before New Zealand became the land of Pinus radiata, it seemed likely that eucalypts would become one of our dominant forest trees. But even before that—before anyone thought of planting forestry trees in New Zealand, because our native forests seemed inexhaustible—eucalypts were being grown here.
Some of the oldest trees were planted by missionaries. A messmate at Orua Bay, near the south head of Manukau Harbour, is thought to have been planted in 1836 by Reverend James Hamlin, when he established a mission station there. Grown from seed, it now towers at the base of a cliff, its branches spreading like an umbrella over nearby baches.
All around the country there are solitary gum trees planted in the most unlikely places. They may be survivors of early group plantings, but it is also possible they were grown specifically for their medicinal value. By the early 1850s, much of the Western world knew of the antimalarial properties of the “fever tree,” or Tasmanian blue gum (E. globulus). It was planted in regions where malaria was common, and for a long time the small amounts of eucalyptus oil given off by its leaves were thought to act as an air purifier. Probably the tree’s main contribution to keeping disease at bay was its habit of drying up swamps in which mosquitoes bred, eucalypts being great consumers of water.
Also by the mid-19th century, kino from Botany Bay ironbark was being used in medicine. Trees that could be used to provide effective treatment for colds, bronchitis, fevers and diarrhoea would have been highly valued by settlers in remote areas. Mother Mary Aubert of the Whanganui River was an advocate of Eucalyptus. In December 1890, she sent a selection of her medicines to the French consul in Wellington, and wrote in her accompanying letter: The Eucalyptus is an antifebrifuge [sic]. A dose is a coffee spoonful repeated three times at half-hour intervals, commencing two hours before the attack. It generally cures in three days. It has been most successful in throat illnesses (the diphtheria of the English), and even, most truthfully, I found it completely successful in a case of authenticated leprosy, also in many cases of bronchial infection, the dose being from four to five drops in a little sweetened water, three or four times a day.
Mother Aubert was not the only one to find eucalyptus preparations efficacious. Maori were using them to treat asthma and to prevent haemorrhaging after childbirth. Today, eucalyptus oil is still used in a variety of remedies. Ironically, in Australia it is imported.
The first local eucalypt plantations were established during the 1860s in areas where there was little timber. The need for quick-growing trees to provide firewood, building timber and shelter saw eucalypts planted by the thousand. On the Canterbury Plains, several prominent settlers put in plantations, among them Thomas W. Adams of Greendale, who planted more than 50 different types.
By the 1870s, the cost of eucalypt hardwood, particularly jarrah (E. marginata), was making itself felt on the government purse. The total cost of timber imports in 1875 was £179,420. From Tasmania alone came 4,375,482 superficial feet (1,333,988 m) of sawn timber, 13,230,270 shingles, 1,995,391 palings and 1107 tons (1125 t) of bark, from which tannins were extracted for leather tanning. Eucalyptus timber was being used for railway works, bridges and culverts, telegraph poles and buildings, including part of the internal structure of Parliament Buildings in Wellington.
As early as 1871 the government had passed the Tree Planting Encouragement Act, with gifts of land as inducement. Then, in 1874, Premier Vogel’s Forest Bill sought to turn three per cent of each province into a forest resource. Captain Campbell Walker, appointed Conservator of State Forests in 1875, spent a year looking at all aspects of forestry around the country and recommended blue gums as the trees to grow for a speedy supply of timber in both Canterbury and Auckland, although he also favoured the planting of conifers and European timbers.
The government set up nurseries to supply seedling gums for planting out. An ounce of seeds (about 23,000) produced an average of 9000 seedlings. By 1889, these were being sold in bundles of 500 for a shilling a hundred.
Seed was readily available to immigrants passing through Tasmania or New South Wales, and those already settled in New Zealand sent to Sydney for it. In 1882, Emily Marshall-White, who is credited with the first plantings of flowering gums in Wanganui, paid a penny a seed for E. ficifolia to a Sydney supplier.
The first portents that locally grown eucalypts might not be the solution to the government’s timber problem arrived with the winters of 1886 and 1899. Severe frosts devastated the Canterbury region. The lowest recorded temperature was –20° C, and Adams reported that only 12 of his species had survived.
Hard winters continued over the first few years of the new century. Not one of Adams’ 500 blue gums survived, though some were over 40 years old. Many acacias also died, and Pinus radiata and cypresses perished en masse.
The next setback Adams and other early foresters faced was an invasion of gum scale insects in 1908. Ladybirds were introduced to control them, and at first they seemed to work, but 10 years later there were more scale outbreaks. To make matters worse, some of the gums on the plains became blackened with blight.
Undaunted by these setbacks, foresters continued to plant eucalypts. In 1909, there were an estimated 3,464,589 eucalyptus trees standing in state plantations, as opposed to 110,161 Pinus radiata. But by then it was recognised that the success of eucalypts was dependent on their being planted in areas with climatic conditions similar to those of the seed source. The value of collecting seed from select trees was also emerging.
In 1913, a Royal Commission on Forestry was established. British forester David Hutchins toured the country and studied the records, and by 1918 had produced a two-volume report. The second part was never published, but it explained why so many of the eucalypt plantings had failed. The fault lay not with the trees, he said, but with the silvicultural practices of the day and the growers’ selection of species: Well-meaning people thought at one time that forestry consisted in getting trees planted against a grant of land and leaving the result to “le bon Dieu.” But if the private plantations showed blunders, the Government plantations were worse! One cannot open the Lands Department’s reports without being shocked . . . dry country trees planted in rainfall areas of 100 in; tender species that are barely extra-tropical planted in cold climates; mediocre species planted in place of valuable ones . . . Of the 29 [species listed as being planted in 1907–8] only nine are much worth planting at all in New Zealand . . . and many of these are being planted in the wrong climates.
While Hutchins blamed foresters for the failure of eucalypt plantations, it is only fair to point out that at that time very little research was being done on the silviculture of gums. Although plantations had been established in Europe, Africa and America, they were still too young to provide much helpful data.
Furthermore, some difficulties were not of the foresters’ making. Harry Bunn, a retired director of the Forest Research Institute and a eucalypt sympathiser, says: “In Australia, the name of a species in one state was often different from its name in another. Some of our foresters wanted to order seed of the E. regnans that grew in Tasmania, where it was called swamp gum, so they ordered swamp gum seeds. Unfortunately, in those days most of the seed came from Woy Woy, in New South Wales, and there swamp gum is E. ovata. It was duly collected from the worst site possible, delivered to New Zealand and planted on all the state plantations, including in the hills behind Whakarewarewa and at Puhipuhi. Of course, it was a dismal failure. After that we started using Latin species names.”
Demand for eucalyptus timber in New Zealand continued to grow after World War I. Eucalypt was need here because few local timbers were rot-resistant when exposed to damp or in-ground conditions; nor were there many strong enough for demanding applications such as bridge building. Some eucalypt timbers met these requirements—but could the trees be grown to harvestable size here? The insidious spread of gum scale, branch gall and twig gall insects was causing increasing concern.
In Canterbury, Blenheim and Nelson—dry districts where gums had grown well and been widely planted—it was common to see gum trees blackened and dead or dying, as if they had been scorched by fire. On the banks of the Waikato River, blue gums, some 30 m high, were dying.
Meanwhile, more effective, less expensive germination, propagation and transplantation techniques were being developed for Pinus radiata. Reduced cost—at a time when the Depression was starting to bite into the forest industry, and the dairy industry was turning to radiata as a substitute for white pine (kahikatea) for butter boxes—gave radiata the edge. The development of commercial pulping methods for tawa and radiata in 1930, and new techniques of wood preservation, further increased the popularity of radiata—and pine forests could be harvested at a younger age than eucalypts: 28 years compared with 40 years. As state-planted timber species, eucalypts were effectively sidelined.
But even if the state had little interest in growing eucalypts in its forests, it was not the only land-holder in the country. Indeed, it was starting to run short of land on which to establish forests. Farmers, meanwhile, had plenty of land, some of it marginal for agriculture, and had always been major users of wood, especially the rot-resistant types. Timber for fence posts, battens, stockyards, gates and bridges was always in demand on farms, and many farmers grew their own supplies. While they could easily produce pine, they couldn’t pressure-treat it for outdoor use, so many remained interested in naturally durable timbers.
In 1957, Neil Barr, a Kaukapakapa farmer with a keen interest in trees, cofounded the Farm Forestry Association, and from the outset eucalypts were a focus for its members. Because the government was keen to see forest plantings continued on lower-quality private land, it introduced a loan scheme to encourage them—the Farm Forestry Act 1962.
Barr, who spent more than 50 years evaluating stands of eucalypts and watching them being milled, reckoned that for sawn timber production the trees needed to have thick trunks. At the centre of each log lies a pith of low-quality compression wood, and beneath the bark lies a band of sapwood—both of little merit. Between these two areas lies a cylinder of valuable timber—but it is only worth milling if the log has a diameter close to a metre.
For a tree to grow a trunk of that thickness, Barr argued, the crown needed a clear space of at least 15 m across. Progressive thinning of young trees from initial densities of 300–800 stems per ha to about 80 stems per ha is also required. High densities are needed in the initial planting to encourage straight, upward growth of the trunk and discourage premature bushiness or the growth of heavy side branches.
Since the 1960s, there has been a modest resurgence of interest in eucalypts. In the hope of encouraging the establishment of local hardwood-based industries, the state carried out limited plantings during the 1970s in its forests. On the Coromandel Peninsula, for example, several hundred hectares were planted during the late 1970s with a view to eventually producing saw-logs.
New Zealand Forest Products, keen to use the trees for pulp and papermaking, also started a eucalypt-planting programme. From 1975 to 1985 it put considerable effort into the Warkworth and Whangarei areas, and planted most of the Kinleith eucalypt resource of 8000 ha, using the species regnans, fastigata (brown barrel), nitens (shining gum) and delegatensis (alpine ash).
Short-fibre pulp—which used to come from tawa but is now sourced from eucalypts—imparts softness to tissues and smoothness to high-quality printing papers. By 1990, Carter Holt Harvey (CHH), which had acquired the Kinleith plantings, had had a change of heart, and decided to sell the wood as chips to Japan.
A few years later, when CHH had another change of heart and decided it wanted to keep the eucalypts after all, more than half the resource had gone. So between 1994 and 1999, another 11,000 ha were planted to feed the kraft pulp mill at Kawerau, but these plantings are not due to come on stream until 2004, when they will start to provide 270,000 m3 a year. Until then there will be something of a shortfall in supplies from the Kinleith forests, which is being made up by harvesting trees from farms and miscellaneous plantings.
Barry Poole, of Hardwood Management, a company which specialises in eucalypts, says that “looking at long-term international statistics, there is a steady 2–2.8 per cent real annual growth in demand for paper for printing and writing purposes.” To manufacture this kind of high-quality paper locally requires eucalypt fibre, and Poole comments that working back from how much paper New Zealand could be selling in a few years’ time reveals the need for 600,000 m3 of timber a year by 2006–7. “To meet that demand, we should be planting 2000 ha of eucs a year, but instead we are only doing 1000 ha, so there will be further shortfalls.”
Another likely use for eucalypts is the manufacture of laminated veneer lumber (LVL) beams. Made from interleaved strips of Douglas fir and eucalypt, these are extremely strong. Radiata pine’s strength is marginal for this application.
One of the larger eucalypt processors and planters in the country is South Wood Export, of Southland. Between 1981 and 1985, it produced beech and kamahi chips for export to Japan from land-clearing operations and logs unfit for milling, but then planted its own eucalypt forests as native milling ceased. Since 1991, South Wood and its daughter companies have planted 800 ha each year in E. nitens, and their plantings now total 12,000 ha, dispersed throughout Southland with a little in south Otago.
One thousand and fifty seedlings are planted per hectare, and are neither thinned nor pruned. Felling will get under way in 2003, and most sites will be harvested—and replanted—when the trees are 12–15 years old. “So far we are just looking at chip production, for which there is a strong demand from Japanese paper companies,” says Graeme Manley, South Wood’s manager, “but we could move into solid wood or veneer production as well.”
At Lyall Dangen’s Ranui mill in West Auckland, a flitch of Sydney blue gum is inspected for quality after being cut from the saw-log. Only a few smaller mills handle eucalypt, as it is a difficult timber to work, requiring frequent blade changes and relatively slow cutting speeds. Hard and durable, the timber lends itself to work surfaces such as benchtops (opposite bottom) and flooring. Northland woodturner Graeme Priddle often chooses eucalypt timber for his work because its hardness enables the wood to hold intricate designs with sharp edges.
Since the 1980s, major eucalypt growers, wood users and the Forest Research Institute have been cooperating to obtain growth and yield data from stands of different species around the country, identifying the most suitable species and improving them by selective breeding, and increasing seed production from superior trees. Average annual growth rates range from 15 to 45 m3 per ha, compared with Pinus radiata rates of 20–35 m3 per ha E.nitens has been found to be the best species to plant at higher elevations in the central North Island and at any altitude in most of the South Island, while E. regnans and E. fastigata are the best species at 200–500 m in the central North Island. Work is being done to develop genetically improved strains, involving techniques to improve flowering and seed production and to rapidly propagate selected varieties.
To control-pollinate trees for breeding purposes, pollen is collected and applied to flowers manually—not easy when flowers may be on twigs 30 m above the forest floor. Some seed collectors detach seed-carrying branches by shooting them off with rifles. There may be more than 300,000 seeds per kg.
Graham Milligan, of Dipton, started exporting eucalyptus seed in 1980 after receiving a query via Neil Barr. An Australian tree seed company was looking for someone who could identify and collect seed from cider gum (E. gunnii), as it was unable to acquire sufficient stock in Australia.
Milligan drove round the country talking to foresters and visiting parks and reserves, and says the “big buzz” of finally finding a magnificent tree and collecting the seed was unforgettable. Since then, he has planted over a hundred eucalypt species and established a seed orchard and nursery.
The destruction of rare trees in a Central Otago town reserve was one of the main reasons behind his venture, he says. The town council, in its ignorance, decided to “tidy up” the area by chopping down the trees, not realising their seeds would have been worth many thousands of dollars.
Milligan regularly collects seed from about 60 different eucalypt species, and exports up to 60 million seeds each year. With a boom in the use of eucalypt foliage in the cut-flower market, he exports to growers the world over, although more than half of his seed goes to Australian seed merchants.
Big forestry companies are interested in eucalypts mainly for pulp and wood chips, but once you’ve handled dressed eucalypt timber—felt its heft and admired its colour and straight grain—pulp seems a terrible waste of fine wood. As with most timber in New Zealand that isn’t pine, however, you’re unlikely to find eucalypt in your local Placemakers or Benchmark store. Only a handful of specialist outlets sell it.
Mike Malloy, a retired lawyer and owner of a forest near Warkworth that includes a good number of eucalypts, thinks the situation is unlikely to change soon. “With pine, there is so much of the stuff that large, integrated companies [such as CHH] not only own the trees but fell, mill, dry, size, use and retail the timber. With eucalypts, as with oak, poplar and other exotics, the resource is small and the integrated companies are not involved. Instead, freshly sawn, undried timber is sold by millers to merchants, who have to get it dried and cleaned up, and then they sell it to end users and manufacturers. Each stage is a different company, and each wants a profit.
“The result is that the end product is expensive, and the grower doesn’t get much of a return. Last year I sold some eucalypt and got slightly less for it than I got for pine—$130–150 a tonne for number 1 grade down to $30 for pulp material. There is no incentive for anyone to plant at those prices, because gums take longer to reach maturity than pines, and are more demanding to grow. Things will only improve when we develop a more integrated processing industry for speciality timbers which cuts out the merchants.”
Despite the low prices currently paid for eucalypt logs, farm foresters continue to plant a variety of gums in the hope that their superior timber will have appreciated by the time they are ready for felling.
“Cynics say there are two types of eucalypt: good firewood and bad firewood, depending on how easy it is to split,” says Peter Davies-Colley. For several years his family ran a combined milling and processing operation called Eucqual, based between Whangarei and Dargaville. The timber they prepared graces the floors of Te Papa (the Museum of New Zealand), among other buildings.
Eucalypt timber needs to be sawn and dried in special ways to prevent warping, splitting, twisting and collapse as it dries. Some species benefit from steam reconditioning—placing the dried timber in a steam bath before giving it a second drying. It was failure to observe these practices that led to the wood getting a bad name in earlier times, says Davies-Colley.
Brian Glamuzina, of St Lukes Timber, in Auckland, buys rough-sawn eucalypt from mills as distant as Kaitaia, Gisborne and Taranaki—anywhere he can source respectable timber—and prepares it for the building industry. His Morningside yard is littered with stacks of rough-sawn timber, air-drying until the moisture content falls to about 30 per cent. It is then kiln-dried until the moisture content drops to 7 or 8 per cent. The combined processes may take six months.
The rough-sawn timber is nondescript, but a stack of 200 mm-wide planed boards looks clean and wonderfully grained, with a richer colour than pine. “The Aussies come over here and gape,” Glamuzina says. “Most of their wood is nothing like this quality. Ninety per cent of it is full of gum pockets and holes.”
Local demand is strong, he says, as architects are increasingly specifying eucalypt for panelling, floors and furniture. “I try to steer customers towards the right timber. Women seem to prefer lighter coloured floors, but a lot of men go for the dark red saligna. I advise the men to get whatever makes their wives happy.”
Like other processors, Glamuzina admits there is a shortage of eucalypt for milling. He could sell more locally if it were available, and Australia and the US would welcome timber from New Zealand. He says there are about eight local species that produce good timber “and a lot of others that are pretty useless. It’s often surprising to find out how people have come to plant the species they have. One old guy in the Wairarapa had pretty good trees and seemed to know a lot, so I asked him where he had picked it up. ‘A POW camp,’ he told me. ‘Our work was planting out eucalypts in Germany. The only book in English in the whole camp was on eucalypts.’ Apparently Hitler was very keen on them.”
While we may have little sympathy for the Führer’s politics, our forestry enterprise could well benefit from an infusion of judiciously chosen eucalyptus. It would provide us with stronger timbers suited to a wider range of uses, cut our need to chemically treat timber to achieve durability and rot resistance, and hedge us against the dangers of monocultures.
Even that “old woman’s medicine chest” eucalypt aroma—present around only a handful of species, as it happens—improves with acquaintance.