The camphor laurel, or camphor tree, Cinnamomum camphora, is undoubtedly one of the best known trees of the northern NSW and southern Queensland. It is also one of the most detested. A native of warm-temperate and sub-tropical areas of East Asia, the species was introduced to Australia by the mid-nineteenth century. From the 1860s it was planted widely in the coastal cities and towns as a shade tree along streets and in parks and other public places. In the sub-tropical Richmond-Tweed district of north-eastern New South Wales, planting accelerated around 1900. By this time clearance of the native rainforests for dairy farming had so denuded the landscape that it became necessary to plant trees to provide shade and shelter for stock. The fast-growing camphor tree was used extensively for this purpose.

Changes in landuse in the Richmond-Tweed district since the 1960s, particularly the transition from intensive dairy farming to extensive beef cattle grazing, and a consequent increase in absentee ownership of land, have led to the proliferation of the camphor tree. The species now exists here in the highest concentration of any area in Australia. The threat which its increasing abundance and weedlike characteristics pose to land managers in the Richmond-Tweed district has led to its recent (August 1999) declaration as a 'noxious weed' across part of its range in north-eastern NSW, imposing obligations upon landowners to remove the plant. In a further attempt to control the spread of the species, efforts are being made to develop and encourage commercial uses for the tree, including the production of timber, and of biomass for power generation, and the distillation of the essential oil.

During 1999, Brett Stubbs (RS&M), with help from David Cameron and Michael O'Neill, conducted a wide-ranging study for the Northern Rivers Regional Development Board and the Northern Rivers Area Consultative Committee into aspects of Cinnamomun camphora, including potential money-making uses for the tree (Stubbs et al., 1999). Their report included a proposed program of research to generate data on the physical and chemical properties of the species in order to facilitate its commercialisation. Little is known at present about these properties in Australian camphor trees, much of the research on the species to date having been focused on methods of killing it.

In its natural range in Asia, C. camphora is known to exist in five chemotypic forms. The leaf and branch oil can be found to be rich in camphor, linalool, 1,8-cineole, nerolidol, or borneol. Based on Japanese studies from the 1960s which discriminated eastern Australian camphor trees on the basis of aroma, two of these five varieties are known to occur in this country. Recent research by Brett Stubbs (RS&M) and Don Brushett (ATTORI), using high-tech instruments rather than trained noses, has confirmed the existence of these two chemotypes in the northeastern NSW population of C. camphora, and has characterised their essential oils. Gas chromatographic analyses undertaken of the leaf oil of trees growing from Sydney to the Tweed River revealed a camphor type, the leaf oil of which contained on average about 70% camphor, and a cineole type, the leaf oil of which contained about 50% 1,8-cineole with less than 1% camphor. The leaf oil itself, it should be noted, constitutes only around 1-2% of the weight of the leaf. The detailed results of this study will be published in a forthcoming edition of Journal of Essential Oil Research (Stubbs and Brushett, in press).

Brett J. Stubbs, Research Fellow.

This article previously published in SCU Forestry News No.1

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