The Pamphlet Collection of Sir Robert Stout: Volume 64
Manuka and Rata
Manuka and Rata.
These trees belong to different branches of the Myrtle family, one of the most extensive in the world. They resemble each other in the quality and appearance of the timber and the bark, but are very different in size of trunk and character of foliage; they also affect different localities and soils.
No. 6. Manuka—Leptospermum scoparium. This is the variety known as white manuka, which is much smaller than the red. It grows best on stiff clayey soils that will scarcely produce anything else, but is common on the margin of large bushes in all the low-lying districts of the province, where it acts as a breakwind to less hardy plants. This tree is best known as an ornamental shrub, but occasionally attains to a diameter of from nine to fifteen inches. Its properties as a timber are generally the same as those of the next variety:—they will be considered further together.
No. 7. Manuka—Leptospermum ericoides. Is common in isolated positions on the whole of the eastern seaboard, and occurs in considerable quantities in the vicinity of Dunedin, Purakanui, and Otepopo. The tree occasionally attains a height of sixty feet, with a diameter of from two to three feet at the butt; but these are extreme sizes—logs thirty feet long and ten inches diameter at the smaller end may be considered the practical limit of page 145 workable timber. So far as habits and habitat are concerned, this tree is identical with the preceding variety. Like most other hardwoods, manuka does not grow straight, and it is much given to warping and cracking; but I do not know that it inherits these defects to a greater extent than is done by jarrah, ironbark, and other Australian timbers of the same class, and it is freer from heart shakes and knots.
Manuka is noted for its great strength and hardness, combined with a considerable amount of toughness, although, as a class, it did not give the highest average. One specimen stood the greatest transverse strain of any Australasian timber tested at the New Zealand Exhibition. Manuka is one of the best timbers in Otago for firewood, consequently there has been a great demand for it, particularly in the vicinity of Dunedin, and the supply is running short; but it is satisfactory to note that young trees grow up rapidly when the old ones are removed. This timber is well adapted for piles in situations where they are kept constantly wet, for swingletrees, spokes, and handles of tools, also for the teeth of wheels. This last is a purpose that requires wood of a particularly good quality, and although not quite so suit-able as rata, manuka has been found to answer admirably. The teeth in the spar-wheels of the "Express" and other coasting steamers are made of manuka, and they are wearing remarkably well.
The old settlers had a high opinion of the durability of manuka, and used it extensively in fencing posts, house blocks, and similar situations of the most trying kind, but it has not proved equal to their expectations. Under ordinary circumstances manuka will decay in the ground in from six to ten years, according to the situation. The longest lived fence that I have heard of is at the Beaumont Ferry, where the posts were not decayed quite through in eleven years. This is, however, an exceptional case, as the fence was erected on dry, porous, alluvial soil, that did not retain moisture. Manuka has proved very durable in marine works;—the great majority of the piles in the old Dunedin Jetty, erected seventeen years ago, were of this timber, and remained quite sound till its removal last month. The George Jetty at Port Chalmers, erected a year later, is in the same condition, but here the test has been more complete—all the other timbers are very much affected by the Limnoria, and the manuka is untouched. Mr. Kirk, in 1874, reported that he had seen manuka fender piles at Port Chalmers much perforated by the Teredo; but the piles he refers to must have been removed since his visit, for there are no signs of the worm in the manuka piles now. The only evidence of its having attacked this timber is in the Bowen Pier, erected four years ago, where one white manuka has been perforated to a small extent.page 146
No. 8. Rata—Metrosideros lucida. This tree grows on high ground at Catlin River and the Longwood Ranges, but descends to sea level at the Bluff, Stewart Island, and the West Coast. It grows best on a light gravelly soil, and attains to a height of thirty or forty feet, and an extreme diameter of about six. Logs can be obtained twenty-four feet long and three feet diameter. The tree sometimes grows with a clear straight stem of this height, but frequently it divides into large branches three or four feet from the ground; this kind furnishes valuable bent timbers for ship-building. Rata has a thin stringy bark like manuka, but larger leaves, and beautiful red flowers. The timber is the heaviest in Otago, being a little heavier than water. It is very dense and solid, with little or no sap-wood, and of a dark red colour like mahogany. Although not nearly so strong, rata is suited for many of the purposes to which manuka is applicable, and has an additional advantage in being larger, straighter grained, and less liable to warp. Its dark colour might render it suitable for furniture, but I fear the absence of figure will be an objection. Hitherto rata has been little utilized. The construction of railway waggons at Invercargill, and the making of teeth and bushes, are almost the only purposes to which it has been applied, but the result is very satisfactory. The bearings of a water-wheel at Waikara are in good order after eighteen years' service, and the railway waggons are pronounced equal to those made from imported timber. Mr. M'Queen prefers rata to any other native wood for teeth and bushes. He says that manuka and kowhai do not wear so well—they wear off in grit or threads, whereas friction only increases the glassy hardness of rata.
Although this timber has not been used in situations that would test its durability, there is every reason to believe that it possesses this property to a considerable extent. I show a sample taken from an old log on a part of the Kaihiku Ranges, where no living rata tree has existed since the settlement of the province. It is still quite sound, and there is a large quantity in the same condition.
No. 9. Kowhai—Sophora tetraptera. This is the sole New Zealand representative of a large genus of the pea tribe, but it is intimately related to the well-known Clianthus of our gardens. The tree, which is of solitary habits, is found in shady damp situations and on light soils in all the seaboard forests. It grows to a height of about forty feet, and has a clear straight stem about twenty-five feet long, and from eighteen inches to three feet in diameter. It seldom exceeds two feet in the vicinity of Dunedin, but from that to three feet is quite common in Southland, particularly at Forest Hill. Kowhai when young has a smooth, tough, and stringy bark, which gets coarse and brittle as the tree approaches maturity. It has beautiful drooping foliage of a feathery appearance, and yellow flowers like laburnum. Altogether page 147 the plant is one of the handsomest in our forests. It is popularly supposed that kowhai is a very slow grower, and the settlers believe that it takes twenty years to produce an axe handle, but this is an erroneous idea. So far as can be determined from the annular rings, an ordinary sized tree reaches maturity in from 150 to 200 years. It should also be noticed that the tree is easily raised from seed, and easily transplanted.
The timber is remarkably straight grained and free from knots, but is subject to a heart-shake that impairs the strength of beams and induces splitting in piles. It is stronger than rata, but weaker than manuka, It is, however, superior to both in toughness, and warps very little. The sapwood, which is clearly defined, is very small; in about 200 logs, ranging from six to twenty-two inches in diameter, it never exceeds one and half inches in thickness. The wood is of a yellow colour like laburnum, but resembles oak in grain and figure. It contains a strong resin or gum, the peculiar smell of which never leaves the timber however well seasoned.
Kowhai is used for the same purposes as manuka and rata, together with fencing posts, house blocks, piles and similar work in a damp situation, for which it is better adapted than either. The screw shaft bearings of the "Betsy Douglas," and the pins and bushes of the paddle floats of the "Coomerang" are of kowhai, and Mr. Sparrow pronounces it equal to lignum vitæ for such work. Messrs. Guthrie and Larnach use this timber extensively for carved work, such as the rims for carriage wheels, the top of circular windows and tilt frames. A good proof of its toughness and straightness of fibre is given in the teeth and bows of hay rakes. The latter are turned to the diameter of a quarter of an inch, and bent into a semicircle of nine inches without sign of giving way.
The durability of kowhai is thoroughly established. It has never boon known to fail in any situation in which it has been tried. But it was scarcely necessary to make a trial, for the old trunks that have been lying in the forests from time immemorial are still as sound as when they fell. Indeed this old timber is frequently used for fencing posts and house blocks. Kowhai has been little used in marine works. The only instance that I know of is some bracing in the old Dunedin jetty, which was perfectly sound after being in place for seventeen years. The same remark applies to fencing and house blocks that have been in use for a much longer period.
No. 10. Fuchsia—Fuchsia excorticata. The fuchsia, which is the parent of many of the cultivated varieties, can scarcely be called a timber tree, but as it possesses many good qualities, and has been applied to useful purposes, it is entitled to a passing notice. The tree, which is found along the seaboard, sometimes attains a height of thirty feet, and a diameter of two feet, but it is so twisted and gnarled that it seldom yields a straight page 148 fencing post. The timber is hard, tough, and imperishable, but much given to warping and cracking. It has been used in house blocks for 20 years without showing symptoms of decay.
No. 11. Broadleaf—Griselinia littoralis. There are few trees in the bush so conspicuous, or so well known as the Broadleaf, which is the sole Otago representative of its species. It is found in all the low-lying forests, but attains its maximum size on the East Coast. It grows to a height of fifty or sixty feet, and a diameter of from three to six; the bark is coarse and fibrous, and the leaves a beautiful deep green of great brilliancy. Although much larger, this tree, like the fuchsia, furnishes very little serviceable timber; it is bent and twisted, irregular outside, and hollow in the heart. The timber is very hard and brittle, and, although crooked, is easily split; it is red in colour, and sometimes prettily marked, and not liable to crack or warp, consequently it would make furniture. Hitherto it has only been used in fencing, house blocks, and knees for boat-building. The durability of broadleaf in any situation is fully established; it has never been known to fail, and old settlers consider it the most lasting of Otago timbers.
No. 12. Kamai—Weinmannia racemosa. There are two trees of this species in New Zealand, but this is the only one in Otago: it belongs, however, to the same order as white mapau, which it resembles slightly. The properties of this timber, and its identity, have for the last year or two been the cause of considerable misconception and confusion throughout the Province. I shall therefore endeavour to describe it so as to clear up all doubts.
As will be seen by the tables of names, kamai is called black birch in the Catlin River District and Southland, which name is given on account of a supposed resemblance to the "birches," or, more correctly, "beeches," a number of which occur in that locality. I cannot understand how such an idea could have originated, for, except in the case of the bark of one, there is not the slightest resemblance between the birches and kamai. Furthermore, the birch that is like in bark is quite unlike in foliage, and it does not grow in the same forest as kamai. Whatever be the reason, the misapplication of names is complete, for the birches are still commonly called kamai in Southland, and this has brought the latter into; disrepute, the birch with which it is most frequently confounded being very subject to decay in damp situations. Kamai is little known on the cast coast, north of the Clutha River, but is common from thence right round the south and west coast to Martin Bay, and particularly plentiful at Catlin River and the western districts. Like the pines, it is rare on high altitudes.
Hitherto this timber has been considered of little value by scientific and professional men; it is described as small, and inferior in strength and page 149 durability. Mr. Kirk questions all its good qualities, and Dr. Hector says "the use of this timber must be guarded against, as it is perfectly worthless." I hope to give it a much better character. Kamai is generally from fifty to seventy feet high, with a trunk from twenty to twenty-five feet long, and eighteen inches to three feet in diameter, but frequently it attains a height of from 80 to 100 feet, and a diameter of from three to four. I am assured that trees of this size are quite common on the fiat land south of Catlin River. Like most hardwoods, this tree does not grow quite straight, but the bonds are not so great as to become a serious defect. The bark, which is of a light grey colour, is very thin, and adheres firmly to the trunk even when dry: the leaves are of a brownish colour, about two inches long and one inch broad, with prickly edges and a sharp stiff point. The wood, which is straight grained, dense, and heavy, has a light brown ground colour, with grey and red figures and streaks, and very conspicuous medullary rays. The streaks are very curious—they look like the broad streaks of a carpenter's pencil drawn at random from top to bottom of the timber, and when dry they form a depression in its surface. Kamai has little or no sap-wood at any stage of its growth, so may be utilized, however small. The growing trees are very much subject to heart decay, few of the oldest ones being fit for sawing into large scantling. When sawn up green and exposed to the sun, this timber cracks and twists to a great extent. A number of logs now in Messrs. Guthrie and Larnach's yard are almost useless through this cause. I find, however, that there is no inordinate splitting or warping in timber that has been seasoned gradually with the bark on, and the ultimate shrinkage under any circumstances is not excessive. The strength of kamai has never been tested; it will, in all probability, stand a considerable strain, but may give way without much warning, as it does not seem to be very flexible. The bark of kamai is rich in tannic acid, consequently it is suitable for tanning leather. An analysis by Mr. Skey, of the bark of towai, a variety found in the North Island, gave thirty-one per cent, of tannic acid, which is nine per cent, richer than the bark of young oak, the best tanning material in England.
This timber is suitable for fencing posts, house blocks, railway sleepers, piles, beams and general framing, but not for boardings or joiners' work. I Being prettily marked, it might be used for turning and other small cabinet-makers' work.
The durability of kamai under the most trying circumstances is, in my opinion, thoroughly established. Mr. Kirk says that he found old specimens in the forest that were much decayed and worm-eaten, but I have never seen I my in which the heart-wood was so affected, and kamai used by the settlers has never been known to fail. I show a section of a tree cut in Seaward page 150 Bush in April, 1802, and which has lain in the forest ever since; it is quite sound and fresh right out to the bark. I also show samples of a tramway sleeper, made from a young tree, that has been in use at the Kew Sawmills, Southland, since 1866; it is still in good preservation. Mr. A. C. Purdie, on a recent visit to Catlin River, kindly collected some valuable information on the subject for me. He found a log that had lain partly buried in the earth for thirteen years quite sound, except about a quarter of an inch of the outside sap, which was beginning to decay. He also was shown saplings that had been used in tramway sleepers for five or six years. Although thus made of immature timber, and tried in the most severe manner, they are still as fresh as when put in. I could multiply similar proofs of the durability of kamai from various districts, and on undoubted authority, so I have no hesitation in giving it a high place for durability. As noticed by Mr. Kirk, it is subject to the ravages of a small boring worm, but the damage done by this animal is too insignificant to be considered a defect in the works for which the timber is best adapted.