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(Cambodia) : rung
(Filipino) : gamboge tree
(Thai) : rong
(Vietnamese) : dang hoang
An evergreen, small to medium-sized tree, up to 15 m tall, with short and straight trunk, up to 20 cm in diameter; bark grey, smooth, 4-6 mm thick, exuding a yellow gum-resin. Leaves opposite, leathery, elliptic or ovate-lanceolate, 10-25 cm x 3-10 cm, cuneate at base, acuminate at apex, shortly stalked. Flowers in clusters or solitary in the axils of fallen leaves, 4-merous, pale yellow and fragrant, unisexual or bisexual; male flowers somewhat smaller than female and bisexuals; sepals leathery, orbicular, 4-6 mm long, persistent; petals ovate, 6-7 mm long; stamens numerous and arranged on an elevated receptacle in male flowers, less numerous and reduced in female flowers; ovary superior, 4-loculed, with sessile stigma. Fruit a globose berry, 2-3 cm in diameter, smooth, with recurved sepals at the base and crowned by the persistent stigma, 1-4 seeded. Seeds 15-20 mm long, surrounded by a pulpy aril. The gum-resin from G. hanburyi is often called Siamese gamboge to distinguish it from the similar product from the bark of G. morella Desr., called Indian gamboge. The species are closely related, and G. hanburyi has been considered in the past as a variety of G. morella.
Ecology and distributionNatural Habitat
Gamboge tree occurs naturally in rain forest.
Gamboge tree is a native of Cambodia, southern Vietnam and Thailand. It has been introduced in Singapore.
Biophysical limitsAltitude: Up to 800 m, Annual rainfall: Up to 2500 mm.
Normally it flowers in November and December and fruits from February to April.
Propagation and management
Functional usesProductsGum or resin: The tree is valued because of the resinous sap, called gamboge, which exudes from incisions in the bark. This sap is used as a golden-yellow colouring matter for varnishes, lacquer, paints, and ink. Medicine: Gamboge is a drastic purgative, an emetic, and a vermifuge for treating tape worm, but it is no longer used in human medicine. Sometimes it is given to cows as purgative. Timber: The wood is sometimes used for interior work.
Gum or resin: The reddish-yellow to brownish-orange sap contains 70-80% resin and 15-25% gum. The main acidic component of the resin is cambogic acid (C38H44O8). The main components of the gum are arabinose (ca. 50%), and galactose (ca. 40%); the gum is soluble in water and forms a yellow emulsion in water. Timber: The wood is pale or brownish-yellow, straight grained, with fine texture, and fairly heavy, weighing about 900 kg/m. It is moderately hard and works easily; it takes a fine polish. Medicine: Gamboge is odourless and tasteless or slightly acid. Large doses of gamboge, administered as a medicine, can be fatal.
Harvesting: Gamboge tree is not in cultivation; only wild trees are tapped. Usually trees are not tapped before they are 20 years old, when the trunk has attained a diameter of about 15 cm. A spiral incision is made in the trunk just below the lowest branches, and the exudate is collected in a bamboo container. About every 3 days the content is poured into smaller bamboo stem parts (about 75 cm long), in which the gum-resin coagulates in about a month or longer. The bamboo containers are then cracked and the gamboge is removed in cylindrical sticks (pipe gamboge), which is the usual form in trade. Sometimes gamboge is moulded and pressed into cakes.
In Singapore, gamboge tree has been planted succesfully. It has never been tried elsewhere in Malesia. As it is apparently well-suited to a moist climate, it is a promising tree for the production of dyeing material and lacquer.
BibliographyChayamarit, K., 1992. Garcinia hanburyi Hook.f. In Lemmens, R.H.M.J. & Wulijarni-Soetjipto, N. (Eds.): Plant Resources of South-East Asia. No. 3: Dye and tannin-producing plants. Prosea Foundation, Bogor, Indonesia. pp. 75-76.
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