Melaleuca alternifolia (PROSEA)
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Introduction |
Melaleuca alternifolia (Maiden & Betche) Cheel
- Family: Myrtaceae
Synonyms
- Melaleuca liniariifolia Smith var. alternifolia Maiden & Betche.
Vernacular names
- Tea tree, narrow-leaved paperbark (En).
Distribution
Australia (from Darling Downs, Queensland to Hunter River, New South Wales), wild and cultivated. It is only occasionally cultivated outside this region, mainly in botanical gardens.
Uses
The valuable essential oil, tea-tree oil or Australian melaleuca oil, is water- or steam-distilled from the leaves and small twigs. This oil is mainly used for medicinal and veterinary purposes as a popular antiseptic because of its ability to penetrate unbroken skin. The oil is also of interest in the perfume industry, as it blends well with other oils while contributing its own distinctive note to soaps, deodorants and colognes.
Observations
- Shrub, up to 7 m tall, with layered, papery bark.
- Leaves variously arranged, scattered to whorled often on one branchlet; petiole 1 mm long; blade linear-acute, 10-35 mm × 1 mm, 3-veined (often only mid-vein visible), puberulous, glabrescent, dotted with oil glands visible with a lens.
- Inflorescence a many-flowered, open to dense, upper-axillary or terminal spike.
- Flowers solitary within each bract with tubular calyx up to 3 mm long and white corolla 2-3 mm long, stamens 30-60, white, clawed, pistil with 3-4 mm long style and capitate stigma.
- Fruit a many-seeded, globose, woody capsule, 2-3 mm in diameter.
M. alternifolia occurs in the warm, wet east coast of Australia, often in swampy circumstances in dense impenetrable thickets, on a range of soils (pH 4.5-7), up to 300 m altitude. Mean summer maximum temperature is 27-31°C, mean minimum 17-19°C, mean winter maximum 18-21°C, mean minimum 6-7°C, and the species is frost sensitive. Average annual rainfall is 1000-1600 mm. Leaf oil content is highest in warmer months. For cultivation, seed is sown in nursery beds, seedlings potted when 4-6 weeks old and transplanted at a density of at least 35 000 trees/ha. Harvesting of leafy twigs starts 15-18 months after establishment and subsequently at 12-15 months intervals. Shoots are cut when less than 2 cm in diameter and at 5-10 cm above soil level. Yield is about 8-10 t/ha, oil content 1-2%. Irrigation is very important. Wild stands have been regularly harvested for 70 years; plantation life is not yet known. The steam-distilled oil is white to pale yellowish-green, with a spicy aromatic odour, combining elements of cardamom, sweet marjoram with a camphoraceous slightly bitter, warm and spicy taste. The major components are terpinen-4-ol (up to 45%), gamma-terpinene (up to 25%), 1,8-cineole (3-17%) and limonene (up to 5%) (% not necessarily from the same sample). See also: Table on standard physical properties. In 1995 Australia produced 200 t of this oil, most of which was exported. Tea tree could be of interest in Malesian areas with suitable circumstances.
Selected sources
- Arctander, S., 1960. Perfume and flavor materials of natural origin. Published by the author, Elizabeth, New Jersey, United States. 736 pp.
- Byrnes, N.B., 1986. A revision of Melaleuca L. (Myrtaceae) in northern and eastern Australia. 1-3. Austrobaileya 2: 65-76, 131-146, 254-273.
- Groom, N., 1997. The new perfume handbook. 2nd edition. Blackie Academic & Professional, London, United Kingdom. 435 pp.
- Guenther, 1949-1952. The essential oils. 6 Vols. D. van Nostrand Co., New York, United States.
- Weiss, E.A., 1997. Essential oil crops. CAB International, Wallingford, United Kingdom. 600 pp.
Physical properties of essential oil
tea tree oil, terpinen-4-ol type
- Relative density : 0.885-0.906
- Refractive index : 1.475-1.482
- Optical rotation : +5° to +15°
- Miscibility in ethanol : 1:2 (85%)
- ISO/EOA : ISO 4730 '96
See comments : Physical properties of essential oils (PROSEA)
Authors
P.C.M. Jansen
