Weed interference in the annual regrowth cycle of plantation tea tree (Melaleuca alternifolia)

Abstract

Tea tree, Melaleuca alternifolia, is an evergreen tree, native to freshwater swamp and creek margins on the mid-eastem coast of Australia. The leaf essential oil has antimicrobial properties, and is used commercially in various health care products, toiletries and cosmetics. Plantation production has been centred on the north coast of New South Wales. Tea trees are planted as seedlings and shoots are first harvested to near-ground level at 12-24 months after planting. Tea tree oil is obtained from the shoot material by steam distillation Tea tree readily coppices, and shoot regrowth from out stumps is harvested on an annual basis. Weed control in tea tree plantations was considered an agronomic research priority. A research project was conducted that investigated the effects, mechanisms and management of weed interference in the annual regrowth cycle of plantation tea tree.

Industry practices at the commencement of the project were recorded in a survey of managers of 28 tea tree plantations in 1992. Managers were interviewed regarding their general plantation management and specific weed control activities. There was much diversity between plantations, particularly in relation to plantation area, planting layout and tree spacings. Weed control methods used included herbicides, mechanical cultivation, hand-hoeing, mowing, grazing, green manure crops, mulches, cover crops and burning. Climatic and soil conditions of plantations were favourable for growth of herbaceous weeds. The majority of plantation managers considered weeds to be a major limit to tea tree oil production, and half were satisfied with their current weed control techniques (for plantations of > 10 ha). Herbicides and cultivation were the most widely used weed control methods. Grazing was rated poorly in terms of weed control, and mowing and hand-hoeing were rated poorly in terms of cost-effectiveness.