Ornamental Eucalypts Provide Durable Timber

Press, Volume CIX, Issue 31983, 9 May 1969, Page 7

Ornamental Eucalypts Provide Durable Timber

The eucalypt species has undoubted ornamental appeal. Ultimate size and frost-resis-tance are the limiting factors to their more widespread use in our gardens. However, their potential as shelter belts and timber trees must not be overlooked. Not only are they the quickest growing hardwood in the world, but with an ultimate height of over 300 feet which some such as Eucalyptus regnans can attain, there is a tremendous potential in very durable timber to be had from one good tree. It takes about 20 years to produce good millable wood, the ■ quality increasing thereafter. Attempts were made in the early days to plant or foster gum trees in New Zealand, in particular on the farm homestead. Much experimentation went on and more remains to be done today as there is still not enough information.

Early work was centred on many lesser known species from Victoria and Tasmania when it was found that most of the renowned species were frost sensitive and difficult to establish by normal nursery methods, in an attempt to find a tree of equal merits to Pinus radiata. Attempts to establish many improbable species, and attack by introducted insects which were kept in check in Australia by predators, tended to reduce interest considerably, although there were some outstanding results from constant trial and error methods of enthusiasts. Eventually it was established that only seed from selected sources would succeed, that seed from New Zealandraised stock was more suited to local conditions and that: performances began to ■ parallel Australian counter-1 parts when grown in similar climates and soils. Frost tolerance is a major factor in success or otherwise of eucalyptus planting. Seedlings raised from New Zealand-grown trees have generally been found to be hardier. Again many species are frost tender when young but can withstand much colder conditions when established. Frost Pockets Varying topography can create local microclimates with up to 10 degrees difference from the warmer upper slopes to' the colder fiats below, and in this respect one must beware of frost pockets created by depressions.

Considerable difference in temperature exists where planting is to be carried out in the shelter of nearby trees or where this is done amidst fern and gorse. However it has been found that trees planted in a grassy sward will withstand about 4

degrees more frost than if planted in bare or’ cultivated land.

Again, sensitivity to frost is greater shortly after planting, or root disturbance of any kind. With this in mind early autumn or late spring planting should be contemplated, in particular in the colder areas.

Deep working of the soil is vital and has been proved to promote more rapid establishment and initial growth. The soil should not be made too fine, thus avoiding excessive aeration which is detrimental to the establish- . ment of young trees.

A nitrogenous fertiliser at planting time is beneficial. A small handful is recommended. This should be well incorporated in the site before planting. After planting all seedlings should be well watered in and thereafter the only attention needed is weed control, which is most important The use of paraquat will be found most helpful in this respect. No detailed recommendations of species can be given as there is not enough information available as yet, other than a listing which is not to be regarded as exhaustive. Frost tolerances are to be taken a guide only. Eucalypts capable of withstanding up to 7 degrees of frost include:

Eucalyptus diverslcolour (also known by its aboriginal name of Karri).. White, bluewhite or pink-White bark depending upon the season, fast growing, attaining a height of about 300 feet; excellent above-ground timber value with valuable bark tannins and nectar producing. Eucalyptus gomophocephala, tuart gum, is eminently suitable for light soils originating as it does from calcereous coastal plains. A grey barked tree, it grows about 150 ft high and possesses very durable timber, eminently suitable for ground work. It is also an excellent source of nectar.

Eucalyptus microcorys, tallow wood, produces a greasy natured all-purpose yellowish timber besides having value as an ornamental and as an abundant source of nectar for bees. Approximate height 150ft-160ft. This tree is very tolerant of shade and is most useful as a gap filler amongst established stands of similar or other trees.

Eucalyptus peniculata, grey ironbark. Anyone conversant i with Australian farming will i know the high esteem in : which the ironbarks are held ■ when it comes to fencing or i similar tasks. They have an . almost unrivalled reputation : for durability. It makes a - rather smaller tree than those I already described and prefers

more nutrious soils and higher rainfall areas. Eucalyptus pilularis is usually black in colour at the base of the trunk, hence the common name Blackbutt. Once predominating as this country’s leading source of railway sleepers this is once again a producer of durable and versatile timber. A height of 200 feet is not uncommon. The tree grows very rapidly in most types of soil and is capable of withstanding coastal conditions. Trees which will tolerate up to 12 degrees of frost include the following: Eucalyptus camaldulesis, probably owes its name of River Red Gum to the fact that its wood is red coloured and in its natural habitat, which is one of the most widespread of all the gums in Australia, it is never found far away from water. In consequence it will be found to make its best growth in moisture-retentive soils although it is unaffected by heat and hot dry winds. It forms a large, spreading tree, up to 140 ft high, of rapid growth and makes an excellent break wind, shelter and shade specimen Its almost year-round flowers provide an exceptional source of honey. Eucalyptus punctata, variously known as grey gum, leather jacket or grey irongum, forms a tree of about 100 ft in height which’ responds best to heavier, moist, clay soils. It is unexcelled as a provider of structural timber. Eucalyptus regnans is known in its local habitat of Tasmania as swamp, gum and may exceed 300 ft in height and grow up to 100 ft or so in girth. It is rapid growing and forms a smooth whitebarked tree except for the base which has a circlet of rough bark. Provides very useful timber for building and pulping. Eucalyptus sieberiana is a smaller growing tree of about 120 ft, being most useful in poor sandy soil. The young trees are very ornamental but gain a deeply furrowed bark with age. It has commendable commercial value but does not provide ground-durable timber. Trees which are capable of withstanding at least 15 degrees frost: Eucalyptus blakelyi, red irongum of New South Wales, forms a small tree under 100 ft. The exceptionally durable and hard timber derived from it .is almost unworkable, but as fencing material it stands with the very best. Most attractive in shape, bud and flower, it requires good, moist soil to thrive to perfection, in which respect a swamp is ideal.

Eucalyptus fastigiata, usually has exceptionally straight grain and yields a very pale brown, hard but light timber which is suitable for all building purposes. It is one of the “stringy barks,” the fibrous bark persisting well into the upper branches. Extremely fast growing and not fastidious as to soil, it may grow to between 60ft and 200 ft.

Eucalyptus obliqua is regarded by some as the only true stringy bark of Tasmania (also known as Tasmanian oak) but called messmate on the mainland. It can form a tree of gigantic proportions in its native states but as yet has failed to yield the same quality timber in New Zealand where it has, however, been grown on inferior ground. The wood is generally used for building and furniture making today. Again variable height may be attained, between 50ft and 200 ft having been recorded. Eucalyptus Smithii, gully ash, produces a light brown hard, heavy and reasonably durable, timber and is distilled for its oils, from a tree which may grow to 150 ft. Alluvial flats suit it best.

Eucalyptus viminalis known as the manna gum or ribbon gum because of the way the yellow-white bark hangs from the upper trunk and branches of the tree. It forms a fairly ornamental tree of use for shade and shelter, yielding distinctive flavoured honey but variable timber quality. Trees for regions exposed to 20 degrees of frost include: Eucalyptus coccifera, mountain peppermint, found in exposed subalpine regions and in consequence is ideally suited for coastal and high country establishment. It forms a small tree up to

110 ft high; more ornamental than of economic value.

Eucalyptus dalrympleana forms a tree up to 150 ft high, the timber of which is not of a high order, being predominantly used for pulping. As a shade and ornamental specimen it has undoubted appeal with white to pink blotched bark which hangs and falls down from the upper region of the tree.

Eucalyptus gigantea (syn. delegantensis) is a tree which may grow in excess of 200 ft and yields a timber useful for a very wide range of purposes, including polished wood and papermaking, but is not ground durable. It has considerable ornamental appeal and does best in better soils and colder climates, disliking humidity. Eucalyptus pauciflora is known as the cabbage tree for a not obvious reason. Although frequently very attractive it does not produce a timber of any merit but makes a reasonably good shelter tree for high elevations

and yields considerable honey. It will burn even when green and may perhaps grow to 60ft.