Melaleuca cajuputi Powell

Evergreen shrub or usually single-stemmed tree up to 25(-40) m tall with an extensive root system, sometimes with aerial adventitious roots. Bark layered, fibrous and papery, grey to white. Crown fairly dense and wide, somewhat silvery in appearance; smaller branches and twigs slender but not drooping, young shoots densely silky hairy with spreading fine hairs up to 2 mm long. Leaves alternate, flat, silky hairy to glabrescent; petiole compressed to concave-convex, 3-7(-11) mm x 1.1-2.3 mm, straight or curved; blade elliptical to lanceolate-elliptical, sometimes obliquely so, 5-10(-12) cm x 1-2.5(-6) cm, 2-10 times longer than wide, attenuated or sometimes abruptly rounded at base, apex acute or narrowly obtuse, often apiculate, thinly coriaceous, dull green, finely but obscurely dotted with oil glands, with 5-7 prominent veins and prominent reticulation. Inflorescence a terminal or upper-axillary spike, single or 2-3 together; spike fairly densely flowered, 3.5-9 cm x 2-2.5 cm; rachis 1-1.3 mm thick, enlarging at anthesis, densely pilose; bracts ovate, striate, villous, caducous; bracteoles absent; flowers in triads, white, greenish-white or creamy; calyx tubular, 2.5-3 mm long, pubescent, tube subcylindrical, 1.2-1.9 mm x 1.5-2 mm, at base adnate to ovary (persistent in fruit), with 4 triangular to semicircular lobes 0.7-0.9 mm x 1.2-2 mm with thin margin; petals 5, broadly obovate- spatulate with a short claw, 2-2.7 mm x 1.8-2.3 mm, blade suborbicular with 7 slender branched veins and streaked with glands; stamens numerous, 7-10 mm long, white, glabrous, arranged in bundles with a claw 1-3.5 mm long; per bundle 7-10 filaments, attached to the upper margin of the claw, free part up to 8 mm long; anthers 0.4-0.55 mm long; pistil with 3-celled ovary about 1 mm long, style 6-9 mm long and a small stigma. Fruit a cup-shaped to globose, many-seeded capsule, 3-3.5 mm x 3.5-4 mm, orifice 1.5-2 mm in diameter with thin valves. Seed linear, minute. M. cajuputi is one of the 10 species that together form the M. leucadendra (L.) L. (also often named M. leucadendron) complex. Many early references to M. leucadendra or M. leucadendron yielding cajeput oil from Indonesia and Vietnam in fact refer to M. cajuputi. It is often difficult to distinguish species within the complex, especially in areas where they overlap, because distinctive characteristics also overlap. Within the complex, M. cajuputi is most closely related to M. viridiflora Sol. ex Gaertner and M. quinquenervia (Cav.) S.T. Blake. Distinctive characteristics are: M. cajuputi has leaves with petiole 3-11 mm long, blade mostly longer than 5 cm and less than 2.5 cm wide, old leaves densely dotted with glands, rather thin in texture, with reticulations almost as prominent as the main veins and young shoots with spreading hairs. M. viridiflora has leaves with petioles 1-2 cm long, blades wider than 2.5 cm, very thick, young shoots with appressed silky hairs. M. quinquenervia is like M. cajuputi but its old leaves are not conspicuously dotted with glands, not thin-textured and have obscure reticulations. Differences in genetic structure between populations east and west of Wallace's line based on allozyme variation led to the hypothesis that M. cajuputi has spread naturally from Australia into South-East Asia, aided by its propensity for invading disturbed sites. M. cajuputi is the only species out of about 250 in Melaleuca L. to occur naturally west of Wallace's Line. M. cajuputi is rather variable and based on differences in morphology, chemical content and geographic distribution 3 subspecies are distinguished: -subsp. cajuputi. Leaf width (6-)10-16(-26) mm; leaf length/width ratio 2.8-9.7; stamens per budle (6-)8-11(-14); stamen bundle claw length 1-1.6 mm. Distribution: Indonesia (Buru, Ceram, Tanimbar Islands, Timor) and Australia (Western Australia, Northern Territory). This is the main source of cajuput oil and is often cultivated. Purely cultivated forms could better be classified as cultivars. -subsp. cumingiana (Turcz.) Barlow. Leaf width (15-)19-28(-39) mm; leaf length/width ratio 2.2-2.9; stamens per bundle (4-)6-8(-10); stamen bundle claw length 2.1-3 mm. Distribution: Burma (Myanmar), Thailand, Vietnam, Peninsular Malaysia, Indonesia (Sumatra, western Java, south-western Kalimantan). Within the natural range of this subspecies, cultivars of subsp. cajuputi occur in plantations sometimes with characteristics intermediate between the 2 subspecies. -subsp. platyphylla Barlow. Leaf width (17-)25-50(-60) mm; leaf length/width ratio 1.3-6.5; stamens per bundle (8-)9-12(-15); stamen bundle claw length 1.1-3.5 mm. Distribution: Indonesia (southern Irian Jaya), Papua New Guinea (southern) and Australia (Queensland).

"Young trees set their first flower buds when only 13-14 months old. Melaleucas appear to be obligate outcrossers and pollination is mainly by insects, but also by birds and small mammals. In Java M. cajuputi flowers throughout the year; in Australia it flowers from March-June and from August-December. Mature seeds have been collected in Australia in October-November."

M. cajuputi grows in a wide range of conditions, but most stands are found on low swampy coastal plains, sometimes immediately behind mangroves that may be flooded to a depth of over one metre during the wet season. The soils are often highly organic alluvial clays with poor drainage and very low fertility, and may be potentially acid sulphate (e.g. the Mekong Delta, Vietnam).

M. cajuputi is primarily found in coastal areas of the hot humid tropics. In its natural habitat the mean maximum temperature of the hottest month is usually 31-33 deg. C and the mean minimum of the coolest month 17-22 deg. C. The area has up to 230 days over 32 deg. C, but few days exceed 38 deg. C. The area is frost-free. Mean annual rainfall is 1300-1750 mm with a strong monsoonal pattern. M. cajuputi grows in a wide range of conditions, but most stands are found on low swampy coastal plains, sometimes immediately behind mangroves that may be flooded to a depth of over one metre during the wet season. The soils are often highly organic alluvial clays with poor drainage and very low fertility, and may be potentially acid sulphate (e.g. the Mekong Delta, Vietnam). It is resistant to fire, tolerates exposure to salt-laden winds, but not to saline waterlogged conditions. In swamps M. cajuputi forms pure forest, mixed open-forest or woodland associated with M. leucadendra (L.) L., Barringtonia acutangula (L.) Gaertn., Lophostemon suaveolens (Sol. ex Gaertn.) Peter G. Wilson & J.T. Waterh. and Nauclea orientalis (L.) L. On less swampy sites it grows with a wide range of eucalypts, acacias and other melaleucas including M. dealbata S.T. Blake, M. saligna Schau. and M. viridiflora Sol. ex Gaertn. Its altitudinal range in Australia is 5-150(-250) m. By contrast, populations in the Moluccas consist of extensive and mostly pure stands that extend inland on infertile, gravelly ridges with a subsoil of red-brown clay. These sites are often colonized by Imperata grassland. Most ridges and slopes of the northern coastline of Buru and those along the Wai Apu River (which drains to the east coast) have sparse vegetation comprising open woodland and low shrubland of M. cajuputi at 30-400 m altitude, covering some 100 000 ha. In western Seram, M. cajuputi occurs as an almost pure, continuous stand of some 150 000 ha along the Hoamoal Peninsula. Scattered populations occur on lowland plains and low undulating ridges at 30-150 m above sea-level elsewhere in Seram and also on the smaller islands between Seram and Buru. Only a few scattered stands of M. cajuputi have been recorded on Ambon. In Vietnam, M. cajuputi forests once occupied most of the seasonally inundated acid sulphate soils (1.5 million ha) of the Mekong Delta, principally on Ca Mau Peninsula, in the Long Xuyen Quadrangle and on the Plain of Reeds. It is estimated that today only 120 000 ha of natural melaleuca forest remain in the Delta.

The exact limits of the natural range of M. cajuputi are not known, as it has been cultivated in Asia for several centuries. M. cajuputi has been planted since 1926 in central Java for oil production, using seed from Buru. It is also planted in Malaysia. The approximate boundaries cover a latitudinal range from 18 deg. South to 12 deg. North from tropical, northern Australia (Queensland, Northern Territory, Western Australia) through south-western Papua New Guinea, Indonesia, Malaysia to Thailand and Vietnam. Natural populations of M. cajuputi in eastern Indonesia occur on the Moluccan Islands of Buru, Seram and Ambon.

Propagation of cajeput is usually by seed. The very small seeds are orthodox and germinate readily in moist, warm conditions with no pretreatment. Viable seed germinates readily, but the tiny seedlings are easily damaged by overhead watering or rain, or may be killed if the sowing mix dries out. In Vietnam the 'bog' technique of watering has been adopted to avoid these problems. This involves standing the germination tray permanently in water so that moisture rises to the surface by capillary action, keeping it constantly moist but not flooded. Seed is sown evenly at a density of about 7000 seeds/m¦. An inflated plastic bag is fitted over the container to maintain a moist environment. After about 4 weeks the seedlings are sturdy enough to withstand overhead watering and the container is removed from the water and handled normally. The risk of fungal disease is high, so good hygiene is essential. After germination the tiny seedlings can be slow to develop, but once under way they grow quickly and their total nursery period is 3(-6) months. Plantations have also been established with small stump plants. M. cajuputi can also be reproduced vegetatively from stem and branch cuttings. After bush fires, M. cajuputi will regenerate by seed, coppicing and from root suckers.

Plantation: In Java, plantations are usually established on degraded land using seedlings of unselected stock at an initial density of 5000 stems per ha. During the first two years plantations may be intercropped with cassava, maize and groundnuts. Husbandry: On seasonally inundated, acid sulphate soils of the Mekong Delta of Vietnam, weeds are a major problem hampering the establishment of M. cajuputi. If left unchecked the prodigious weed growth becomes a major fire hazard during the dry season. Intercropping ensures adequate weed control. There is some small-scale mulching of plants with the spent leaves left after oil extraction; this practice merits more widespread application. No artificial fertilizers are applied.

Pests: Young cajeput trees in Java, especially West Java, are attacked by subterranean termites (Macrotermes gilvus, M. insperatus and Odontotermes grandiceps) which attack the bark and wood, causing the trunk to split. Trees whose roots have been attacked may die. Newly planted stumps are most seriously affected. Up to 50% of the trees may be damaged before they are 2 years old. Often as many as 5-6 replantings are needed to replace all dead trees.

On average there are 2 700 000 viable seeds per kg.

Apiculture: M. cajuputi is an important honey tree. Shade or shelter: It makes an excellent shade and shelter tree. Reclamation: It is one of the few trees that can be grown successfully to reforest exposed locations on brackish soils and acid sulphate soils. Other services: The tree often plays an important role in estuarine environments where it provides habitat for birds, fish and shrimps.

Medicine: The leaves of M. cajuputi possess antibacterial, anti-inflammatory and anodyne properties and are used traditionally against pain, burns, colds, influenza and dyspepsia. Cajeput oil is produced from the leaves by steam distillation. The oil is a common household medicine, especially in South-East Asia, used internally for the treatment of coughs and colds, against stomach cramps, colic and asthma. It is used externally for the relief of neuralgia and rheumatism, often in the form of ointments and liniments, and for the relief of toothache and earache. It is also applied in treating indolent tumours. Poison: The oil is reputed to have insect-repellent properties; it is a sedative and relaxant and is useful in treating worms, particularly roundworm, and infections of the genito-urinary system. Other products: It is used as a flavouring in cooking and as a fragrance and freshening agent in soaps, cosmetics, detergents and perfumes. Timber: The wood of M. cajuputi is hard and fairly heavy and makes good fuelwood. Of limited interest for sawmilling, it is generally used in the round or roughly fashioned and is suitable for posts, poles and piles. The timber tends to check and warp, but when carefully seasoned it is suitable for general construction and flooring. The soft bark is used as a packing material, in boat building, filling mattresses or pillows and for insulation.