Leptospermum (PROSEA)
Introduction |
Leptospermum J.R. Forster & J.G. Forster
- Protologue: Charact. gen. pl.: 71, t. 36 (1775).
- Family: Myrtaceae
- Chromosome number: x= 11; for all species investigated: 2n= 22
Vernacular names
- Mountain gelam, tea tree, ti tree (En)
- Malaysia: China maki, gelam bukit (Peninsular)
- Philippines: malasulasi (Filipino).
Origin and geographic distribution
Leptospermum comprises about 80 species and occurs in Burma (Myanmar), southern Thailand, throughout Malesia to Australia, the Caroline Islands and New Zealand. Australia is richest in species (28, most of them in Queensland). In Malesia only 4 species are found, 2 of which occur only locally ( L. parviflorum Valeton in the lowlands of New Guinea and L. recurvum Hook. f. on Mount Kinabalu, Sabah, and in the mountains of Sulawesi); the other 2 species ( L. amboinense and L. javanicum ) are widespread.
Uses
The wood of Leptospermum is used for small objects such as tool handles and for firewood. It is suitable for rafters in house building because of its durability.
In the Moluccas small amounts of volatile oil are distilled from the leaves, which are inhaled against bronchitis and used as an embrocation against rheumatism. A tea made from the leaves is drunk as stimulant.
Production and international trade
Due to its small size, utilization of Leptospermum timber is scarce and on a local scale only.
Properties
Leptospermum yields a heavy hardwood with a density of 950-1040 kg/m3at 15% moisture content. Heartwood brown with darker streaks, moderately sharply differentiated from the paler sapwood; grain wavy or interlocked; texture rather fine and even. Growth rings distinct to indistinct, boundaries indicated by layers of denser fibres and fewer vessels; vessels variable in size from very small to medium-sized, predominantly solitary, sometimes in radial pairs, occasionally in vague tangential arrangement, open or filled with gum-like deposits; parenchyma moderately abundant, apotracheal diffuse tending to local aggregation, paratracheal scanty, with tendency to aliform, indistinct even with a lens; rays moderately fine, not visible to the naked eye; ripple marks absent.
The wood is hard, very strong and durable when exposed to the weather or in contact with the ground. The wood is probably resistant to sap-stain fungi. The sapwood is non-susceptible to Lyctus .
See also the table on microscopic wood anatomy.
Botany
Shrubs or small trees up to 12(-16) m tall; bole often crooked, sometimes straight, up to 20 cm in diameter; bark surface usually deeply fissured and flaky, greyish-brown; branches often gnarled and twisted. Twigs with raised ridges extending from the base of each leaf. Leaves arranged spirally, simple, sessile, entire, usually with 3 longitudinal veins, aromatic when crushed; stipules minute, caducous. Flowers axillary, usually solitary and sessile, with 2 bracteoles, 5-merous; calyx cup-shaped, lobed, swollen; petals free, white, caducous; stamens many, in a single whorl, free, shorter than petals, with versatile anthers; ovary semi-inferior, usually 5-locular with many ovules in each cell, style 1. Fruit a small woody capsule, seated in the persistent calyx cup, many-seeded, opening at the top with 5 slits. Seed linear. Seedling with epigeal germination; first few leaves opposite, subsequent ones arranged spirally.
Leptospermum is known to form ecto-mycorrhizae, but has also been observed to have vesicular-arbuscular endo-mycorrhizae simultaneously, which is extremely rare. Flowering is probably throughout the year. Some trees of L. recurvum exhibit andromonoecism, i.e. have bisexual and functionally male flowers on the same tree.
L. amboinense and L. javanicum have often been considered as conspecific; this species was then usually called L. flavescens J.E. Smith. Recently it was discovered that in Malesia 2 distinct species are involved which differ in the shape of the leaves (obovate and discolourous in L. javanicum , lanceolate and concolourous in L. amboinense ), the pubescence of the hypanthium (pubescent in L. javanicum , mostly glabrous in L. amboinense ) and the size of the fruit (larger in L. javanicum ). The "true" L. flavescens is now considered a synonym of the Australian species L. polygalifolium Salisb.
Ecology
Leptospermum species are light-demanding, colonizing clearings in upper montane forest. They usually grow on rocky cliffs or ridges in the mountains up to 3000(-4000) m altitude and are often gregarious. L. amboinense is found at altitudes of up to 2000 m, L. javanicum often occurs higher in the mountains at 1500-3000 m altitude and may become dominant. At higher altitudes and in exposed locations with shallow soils the habit is a heather-like bush, whereas in bogs the plants may look like a woody herb. However, they are reported as trees with a bole up to 20 cm in diameter locally in Peninsular Malaysia at 1000-1500 m altitude, and as a tree up to 15 m tall with a straight slender bole in the Moluccas at 250-400 m altitude. In South Sulawesi Leptospermum species thrive on soils degraded due to fire, grazing and erosion.
Silviculture Leptospermum species have pioneer characteristics but lack the aggressiveness of true pioneers. No seed counts are available for Malesian species, but L. liversidgei R.T. Baker & H.G. Smith from New South Wales (Australia) has about 1.5 million dry clean seeds/kg. The latter has been planted in Java, but all trees died.
Genetic resources and breeding
Although some Leptospermum species have a very restricted area of distribution, they seem not to be endangered in South-East Asia because their timber is not in great demand and they often grow in inaccessible mountanous locations.
Prospects
Since the size of Leptospermum trees is too small and the shape of the bole too poor it is unlikely that the use of the timber will increase.
Literature
95, 97, 163, 209, 267, 405, 427, 436, 674, 861, 1097, 1219, 1221, 1237, 1242.