Melaleuca quinquenervia (PROSEA)
Melaleuca quinquenervia (Cav.) S.T. Blake
- Protologue: Proc. Roy. Soc. Queensl. 69: 76 (1958).
- Family: Myrtaceae
- Chromosome number: 2n= 22
- Metrosideros quinquenervia Cav. (1797),
- Melaleuca viridiflora Sol. ex Gaertner var. rubriflora Brong. & Gris (1864),
- M. viridiflora Sol. ex Gaertner var. angustifolia (L.f.) N.B. Byrnes (1984), non Blume (1826).
- Broad-leaved paperbark, broad-leaved tea tree, belbowrie (En). Punk tree, melaleuca (Am).
- Niaouli (Fr)
- Indonesia: kayu putih.
Origin and geographic distribution
M. quinquenervia is native to the coastal region of eastern Australia, from near Sydney in New South Wales to Cape York in northern Queensland. It also occurs in southern New Guinea and has an extensive distribution in New Caledonia, especially in the north-western part of the island. The latitudinal range of the natural occurrence is 8-34S. M. quinquenervia has been planted in the tropical lowlands of the Philippines, India, the West Indies, Guyana and in the United States (Hawaii and Florida) and probably in Madagascar. In southern Florida, it has escaped cultivation and has become weedy in seasonally wet locations.
The leaves of M. quinquenervia are a source of a cineole-rich essential oil called niaouli oil or gomen oil used in pharmaceutical preparations e.g. to flavour cough drops, gargles and toothpastes and in aromatherapy. In France, where its pharmaceutical use has a long tradition, it sometimes replaces cajeput oil and eucalypt oil in the treatment of coughs including whooping cough, rheumatism, neuralgia and chronic catarrhs of the pulmonary membrane. M. quinquenervia is often grown as a wind-break and as an ornamental. A strong flavoured, low density honey is produced from the abundant flowers. The wood is an excellent fuel and makes good quality charcoal. As timber it is suitable for pit props, fence posts and rails, flooring, house timbers and pulp. The bark may be used as mulch in potting mixes, for packaging and insulation.
Production and international trade
Production statistics of niaouli oil are very scarce and incomplete. The world production of niaouli oil in 1997 had an estimated value of US$ 67 000. Production in New Caledonia was estimated at 2-2.5 t in 1980, 4 t in 1985 and 7-10 t in 1998, down from an average of 20 t/year prior to the Second World War and during the early 1950s. No statistics are available on the area of the world planted to M. quinquenervia. Two million trees have been planted on State Forest Reserve land in Hawaii. The largest area planted to it, however, is in Florida, where it has naturalized and is dominant over almost 200 000 ha, with pure stands covering 16 000 ha.
The leaf oils of M. quinquenervia fall into 2 classes based on their chemical composition. One chemotype is rich in nerolidol (90%), while the other is rich in 1,8-cineole (30-70%) and sometimes in viridiflorol (0-60%). The cineole-rich chemotype is the source of niaouli oil produced in New Caledonia. Niaouli oil is a pale yellow to greenish-yellow or almost colourless liquid with a strong, fresh, sweet-camphoraceous, but cooling odour, reminiscent of cajeput oil, eucalypt oil and cardamom oil, though less spicy than the latter. It has a slight off-taste of bitter almonds. The flavour is warm, only slightly astringent, aromatic and somewhat sweet. Its sweetness in odour and flavour is quite characteristic and different from eucalypt oil and cajeput oil. The odour of bitter almonds is attributed to the presence of benzaldehyde. Besides cineole and viridiflorol, it containsα-terpineol and several of its esters, α-pinene and β-caryophyllene. See also: Composition of essential-oil samples. There are reports from Florida that exudates from the flowers cause respiratory irritation in sensitive persons.
The sapwood is pale yellow to pink. The heartwood is pink to reddish brown, rippled with light and dark tones, hard, fine-textured and diffuse, porous, tending to warp and difficult to season. It can produce a nice finish. It contains silica. The basic density of the heartwood is generally 490-550 kg/m3, and air-dry density 700-750 kg/m3. The energy values of the wood and bark are 18 400 and 25 800 kJ/kg, respectively. The wood is an excellent fuel, but the bark of old trees has to be peeled off because only the outer layers burn. Problems caused by the dust from the bark of mature trees and the low density of the bark can be overcome by adapted burning systems. The bark of young trees has a greater energy value than the wood. Durability of untreated posts in contact with the ground is poor; posts must be replaced after about 3 years. Silica in the wood rapidly blunts saws and planes. To minimize checking and warping, the wood must be dried carefully. Collapse is slight. Shrinkage is about 3.5% radially and 7% tangentially.
There are 1.5-5 million viable seeds per kg of seed and chaff mix.
Adulterations and substitutes
Niaouli oil is occasionally adulterated with kerosene or fatty acids. A very high cineole content may indicate adulteration with cheaper eucalypt oil. Eucalypt oil with small amounts of admixtures is commonly used as a substitute for niaouli oil.
- A small to medium-sized tree, (4-)8-12(-25) m tall. Trunk moderately straight to crooked; bark thick, made up of many papery layers that split and peel, rough and shaggy on large trunks; crown narrow and open, or fairly dense, dull green or slightly yellowish-green; twigs pendulous, densely hairy when young.
- Leaves alternate, scattered, glabrescent; petiole compressed, 4-10 mm × 1.5-2.4 mm; blade lanceolate to oblanceolate, 5-9 cm × 0.6-2.4 cm, mostly 4-6 times longer than wide, straight or oblique, rarely slightly falcate, dull green, coriaceous, stiff, base narrowly attenuate, margin entire, apex acute or obtuse, sometimes apiculate, main veins 5, rarely 3 or 7, prominent, parallel from base to tip, reticulation indistinct, oil glands usually obscure.
- Inflorescence a many-flowered, terminal or sometimes upper-axillary, dense to moderately open spike, often 2-4 together, 4-8.5 cm × 2.5-3.5 cm; rachis 1-1.8 mm wide, glabrous to hairy.
- Flowers in triads, usually white or creamy white, rarely greenish or reddish; calyx tubular, 3-4 mm long; tube subcylindrical, 2-2.5 mm long, persistent, with 4 semi-circular lobes, 1-1.8 mm long, margins hyaline; petals 5, obovate-spatulate, deeply concave, 3-3.5 mm × 2-2.5 mm, with a short claw, white or red; stamens in 5 bundles of 6-9 each, conspicuous, 11-20 mm long, anthers 0.6-0.8 mm long, claw 1.5-2 mm long.
- Fruit a broadly cylindrical, thick-walled capsule, 3.5-4 mm × 4-5 mm, grey-brown, persistent; orifice 2.5-4 mm in diameter.
- Seed tapering from the dorsal end, about 1.0 mm × 0.3 mm, pale-brown.
Growth and development
Seedling plants of M. quinquenervia can grow 0.9-1.8 m/year. In Florida, they may grow throughout the year, but growth is most rapid in spring to early summer, and in late summer to early autumn. In trial plantings on two locations in south-eastern Queensland (Australia) a provenance from northern Queensland averaged 4.3 m in height and 15 cm in diameter at ground level at 4.5 years. In Hawaii, trees in plantations on good sites may reach 18 m in height and 50 cm in diameter in 40 years. Formation of vesicular-arbuscular mycorrhizae and ectomycorrhizae has been found in Australia. Flowering commences as early as 3 years after sowing. M. quinquenervia coppices readily, but root suckers are not commonly produced. The usual flowering time in Australia is autumn and winter, but flowers may be present at other times or throughout the year. Pollination is by insects and a high rate of outcrossing is assumed. Seed ripens in spring and summer. They are shed through 3-4 slits positioned horizontally below the capsule rim. The spike, which produces 30-70 densely packed woody, stalkless capsules, grows out into a leafy twig beyond the fruits.
Other botanical information
M. quinquenervia belongs to the Melaleuca leucadendra (L.) L. (also named Melaleuca leucadendron) species complex: a group of 10 closely related species. It is often difficult to distinguish the individual species within the complex, especially in areas where the species overlap, because distinctive characteristics overlap as well and sometimes intermediate forms occur. Within the complex M. quinquenervia is most closely related to M. cajuputi Powell and M. viridiflora Sol. ex Gaertner. Distinctive characteristics are: M. cajuputi has leaves with 3-11 mm long petiole, blade mostly longer than 5 cm and less than 2.5 cm wide, old ones dotted with fine glands, rather thin, reticulations are about as prominent as the main veins and young shoots have spreading hairs. M. quinquenervia is like M. cajuputi but its old leaves are not dotted with conspicuous glands, not thin and have relatively obscure reticulations. M. viridiflora has leaves with 1-2 cm long petiole, blade wider than 2.5 cm, very thick, young shoots with appressed silky hairs. Some authors consider M. quinquenervia to be a variety of M. viridiflora Sol. ex Gaertner (var. rubriflora Brong. & Gris), but this reduction is rarely followed.
In Australia and Papua New Guinea, M. quinquenervia is generally confined to the lowlands, below 100 m, but in New Caledonia it forms extensive stands up to an altitude of 900-1000 m. It occurs in the warm subhumid and humid zones. In Australia, the mean maximum temperature of the hottest month ranges from 26°C in the south to 34°C in the north. The corresponding mean minimum temperatures of the coolest month are 4°C and 20°C. A few frosts may occur in its habitat in southern Australia. Average annual rainfall is about 900-1250 mm; the seasonal distribution pattern varies from a moderate summer-autumn maximum in southern Australia to a strong monsoonal pattern in the north.
In Australia, M. quinquenervia generally grows on level or gently undulating coastal lowlands. It grows along streams, fringing tidal estuaries, and frequently forms pure stands in freshwater swamps. It often occurs close to the beach and will tolerate wind-blown salt. Trees are highly fire-tolerant during all but the early seedling stages. The soils are often peaty humic gleys, sandy at the surface but silty or clayey below and with a high organic matter content. The water table is near or above the surface for most of the year. M. quinquenervia appears to tolerate a low level of groundwater salinity, although this reduces growth. In Papua New Guinea it occurs on coastal, non-tidal, highly organic, alluvial clay plains with poor drainage and very low fertility. The plains may be flooded to more than 1 m deep during the wet season. In New Caledonia M. quinquenervia occurs extensively on well-drained slopes and ridges in the uplands. It grows on all soil types but is rarely found on soils derived from ultrabasic rock.
M. quinquenervia is usually dominant and frequently occurs in almost pure stands. The best-developed stands on favourable sites occur as open forest and woodland, but elsewhere stands are reduced to low woodland or tall scrub.
M. quinquenervia was first introduced to Florida as an ornamental and for afforestation of the grassy plains of the Everglades in the early 1900s. It is now regarded as a noxious weed there. Seed disperses naturally and establishes readily in wetlands. Unmanaged stands may have a density of 7 000-20 000 stems/ha thus crowding out native vegetation and wildlife habitats and reducing native biodiversity by 60-80% in wet prairie and marsh communities of the Everglades.
Propagation and planting
Propagation of M. quinquenervia is by seed which can be sown either in seedbeds or directly into nursery containers. Mature seed germinates readily and does not require pretreatment. Seeds are very small, so care is needed to ensure that the sowing mix does not dry out, any diseases are avoided or controlled and that seeds and small seedlings are not damaged or washed away by careless watering. Watering from below instead of from above may be used to avoid the latter problem. Conventional nursery procedures will produce healthy, vigorous seedlings suitable for planting in about 4-7 months from sowing. When seedlings are 2-3 cm tall (4-8 weeks after sowing), they are either transplanted or thinned, depending on the method used. Many Melaleuca species are propagated vegetatively from cuttings or by micropropagation, and these techniques might also be successful with M. quinquenervia. Planting out at routine plantation spacings (e.g. 2-3 m × 2 m) is appropriate for most purposes.
M. quinquenervia can successfully compete with weeds but early weed control will improve growth rates. The fungus Botryosphaeria ribis holds promise as a biological control agent of weedy M. quinquenervia in Florida.
Diseases and pests
A large number of insects feed on M. quinquenervia in Australia but damage remains localized. The heartwood lacks resistance to damage by fungi, termites and marine borers. As an exotic, it is relatively free of diseases and pests.
Leaves for niaouli oil production are collected from natural stands only, by slashing branches and stripping the leaves. One man can collect 300-500 kg leaves per day.
When grown for its wood, M. quinquenervia is most commonly grown on relatively short coppice rotations that maximize the production of small-sized logs suitable for fuelwood, posts, piles and poles.
No information is available on the yield of leaves of M. quinquenervia. Logs of 45 cm in diameter can be produced in 10-12 years. First-year coppice yields from established stands in Florida have averaged 3-4 t/ha of dry wood.
Handling after harvest
Niaouli oil is obtained by steam distillation of the leaves. In New Caledonia only a few, traditional, direct-fired stills remain in use today.
M. quinquenervia remains relatively common throughout its wide geographical range. Given the variation in its natural habitat, genetic differences in growth and adaptation are likely to be found and careful selection of seed sources for specific environments may lead to improved performance. The Australian Tree Seed Centre, CSIRO Division of Forestry in Canberra is assembling range-wide seed collections of tropical Melaleuca species, including M. quinquenervia.
There are no known selection and breeding programmes at the present time. M. quinquenervia has recently been introduced to Vietnam for provenance trials.
The production of niaouli oil has declined mainly because of the high cost of local labour. As a very similar oil can be produced from cheap eucalypt oil, the production of niaouli oil is unlikely to recover in the near future. The best prospects for widespread use of M. quinquenervia in forestry are on swampy sites, as more productive species are already available for better-drained habitats. It has a demonstrated ability to establish and grow moderately rapidly in areas of the humid and subhumid tropics that may be inundated for months. Its use will be limited by the extent of swampy environments available for reforestation and its relative performance in comparison with some closely related, similarly-adapted Melaleuca species like M. leucadendra and M. cajuputi.
The introduction of M. quinquenervia and its close relatives should always be carefully considered and proceed with caution, in view of its potential to become a weed.
- Blake, S.T., 1968. A revision of Melaleuca leucadendron and its allies (Myrtaceae). Contributions from the Queensland Herbarium No 1. Queensland Herbarium, Department of Primary Industries, Brisbane, Australia. 113 pp.
- Boland, D.J., Brooker, M.I.H. & Chippendale, G.M., 1992. Forest trees of Australia. 4th edition. Commonwealth Scientific and Industrial Research Organization, East Melbourne, Australia. pp. 568-570.
- 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.
- Cherrier, J.F., 1981. Le niaouli en Nouvelle-Calédonie (Melaleuca quinquenervia S.T. Blake) [Broad-leaved paperbark in New Caledonia]. Revue Forestière Française 33: 297-311.
- Geiger, R.K. (Editor), 1981. Proceedings of Melaleuca Symposium, September 23-24, 1980. Florida Department of Agriculture and Consumer Services, Division of Forestry, Tallahassee, Florida, United States. 140 pp.
- Ramanoelina, P.A.R., Bianchini, J.P., Andriantsiferana, M., Viano, J. & Gaydou, E.M., 1992. Chemical composition of niaouli essential oils from Madagascar. Journal of Essential Oil Research 4: 657-658.
- Ramanoelina, P.A.R., Viano, J., Bianchini, J.P. & Gaydou, E.M., 1994. Occurrence of various chemotypes in niaouli (M. quinquenervia) essential oils from Madagascar. Journal of Agricultural and Food Chemistry 42: 1177-1182.
- Rayachhetry, M.B., Blakeslee, G.M. & Center, T.D., 1996. Predisposition of melaleuca (Melaleuca quinquenervia) to invasion by the potential biological control agent Botryosphaeria ribis. Weed Science 44: 603-608.
- Wang, S., Huffman, J.B. & Littel, R.C., 1981. Characterization of Melaleuca biomass as fuel for direct combustion. Wood Science 13: 216-219.
- Trilles, B., Bouraïma-Madjebi, S. & Valet, G., 1998. Melaleuca quinquenervia (Cavanilles) S.T. Blake, Niaouli. In: Southwell, I.A. & Lowe, B. (Editors): Medicinal and aromatic plants -Industrial profiles- Tea tree, the genus Melaleuca. Harwood Academic Publishers, Amsterdam, the Netherlands (in press).
J.C. Doran & J.W. Turnbull