Garcinia (PROSEA Timbers)

Plant Resources of South-East Asia Introduction

List of species

Garcinia L.

Protologue: Sp. pl. 1: 443 (1753); Gen. pl., ed. 5: 202 (1754).

Family: Guttiferae

Chromosome number: x= 8, 16;G. atroviridisGriffith ex T. Anderson: 2n= 60,G. cowa:n= 26,G. hanburyiHook. f.: 2n= 44,G. hombroniana: 2n= 48, 76,G. mangostana: 2n= 56-76, 88-90, 96, 98-110, 120-130,G. nervosa: 2n= 56,G. parvifolia: 2n= 44, 72, 88,G. prainianaKing: 2n= 60,G. xanthochymusHook. f.: 2n= 72, 80, 96

Vernacular names

• Kandis (trade name). Garcinia (En)
• Philippines: bunog
• Thailand: cha muang
• Vietnam: bứa.

Origin and geographic distribution

Garcinia probably comprises some 200 species, mainly in the Old World tropics and a few species in tropical America. South-East Asia is the main centre of diversity, with around 100 species.

Uses

Garcinia is used for temporary construction, poles, interior trim, furniture and fencing. The heavier species are suitable for semi-permanent constructions, posts, beams, joists, rafters, bridge building, piling, flooring, paving blocks, vehicle bodies, shingles, tool handles, wooden pegs, rulers, turnery, chessmen and pallets. The wood yields a very good charcoal.

Several species are well-known fruit trees, the most important being the mangosteen ( G. mangostana ). Fruits of some species are sour and made into jams, used as a substitute for tamarind or to fix dyes. The rind of the green fruit is often dried and used as a condiment. The seed of some species contains an edible oil. The yellow latex of G. hanburyi from Thailand and G. morella (Gaertn.) Desr. from India is the source of "gamboge" paint. Leaves of G. cowa can be eaten as a vegetable either raw or in curries and have a sour taste. A decoction of the roots of G. hombroniana is given after childbirth; both roots and leaves have been applied for itch.

Production and international trade

Garcinia wood generally enters the market in mixed consignments of medium-weight hardwood. In 1992 only 116 m³of logs with a value of about US$ 50 000 was exported from Sabah. In 1996 the export of Garcinia logs from Papua New Guinea amounted to 30 000 m³with an average free-on-board (FOB) price of 98/m³.

Properties

Garcinia yields a medium-weight to heavy hardwood with a density of 690-1120 kg/m³at 15% moisture content, although for G. parvifolia 410 kg/m³has also been recorded. Heartwood variable in colour, yellow in many species but red to dark red-brown in a few others (e.g. G. hombroniana and G. malaccensis ), usually not clearly differentiated from the paler, rather wide sapwood, in G. hombroniana the red-brown sapwood is distinct from the dark red-brown heartwood; grain straight or slightly irregular; texture fine to moderately fine and even; parenchyma conspicuous in yellow timbers on tangential surface. Growth rings indistinct or visible due to colour differences or fewer parenchyma bands; vessels very small to medium-sized, solitary and in radial multiples of 2-5 and with occasional clusters, reddish-yellow gum deposits sometimes abundant, tyloses very rare; parenchyma moderately abundant to abundant, apotracheal in interrupted, narrow bands, and paratracheal vasicentric, aliform or confluent; rays very fine to medium-sized; ripple marks absent; radial canals observed in G. cowa .

Shrinkage of the wood when seasoned is high to very high and it is susceptible to checking; back-sawn boards are particularly likely to warp considerably. The wood is moderately hard to very hard and moderately strong to very strong. It is easy to saw and finishes well, but the harder timber is difficult to work and dulls cutting edges of tools. The wood is usually moderately durable but is very durable in some species like G. ituman . The heartwood is reportedly resistant to pressure treatment although for G. latissima a retention of about 320 kg/m³has been determined. The heartwood is moderately resistant to resistant to dry-wood termites. The sapwood is non-susceptible to Lyctus in some species but susceptible in others.

See also the tables on microscopic wood anatomy and wood properties.

Botany

Evergreen, generally dioecious shrubs or small to medium-sized trees up to 25(-33) m tall; bole straight, branchless for up to 18 m, up to 60(-100) cm in diameter, occasionally with small buttresses, often knobbly; bark surface smooth to adherent scaly, dark brown or black, inner bark yellow, with often copious yellow or sometimes white exudate; crown dense, often narrowly conical. Twigs square. Leaves decussate, but successive pairs in 1 plane by torsion of the twig, simple, entire, clasping the twig at base and the uppermost pair concealing the terminal bud; stipules absent. Inflorescence axillary. Flowers solitary or in small clusters or occasionally short racemes, unisexual, 4-5-merous; sepals rather fleshy, persistent in fruit; petals rather fleshy, white, yellow or reddish. Male flower with many stamens which are united in 4-5 bundles or a lobed ring or in a central globose mass, anthers sessile, with 2 or 4 cells; ovary present or absent. Female flower with a superior, 4-5(-12)-locular ovary with a single ovule in each cell, stigma large and often conspicuous. Fruit a leathery to woody berry with 1 to several seeds, tipped with the stigmatic remains. Seed with arillode. Seedling with hypogeal germination; cotyledons not emergent; hypocotyl elongated; the shoot emerging from one end of the seed, the root from the other; first few leaves scale-like, all leaves decussate, conduplicate.

Trees show monopodial growth. Branches arise from the trunk at an acute angle, then curve horizontally or droop. Growth is generally slow. Young leaves are pink. Apomixis is common in Garcinia : many species can produce seed asexually as well as sexually. Polyembryony is also quite common. Wild species flower at night and have a characteristic strong odour. Nectar is secreted on stigmas and pollination is by insects; G. hombroniana is pollinated by Trigona bees. Flowering is seasonal, usually after a period of pronounced dry weather. In Peninsular Malaysia G. parvifolia flowers regularly in February-April, G. hombroniana from January to June. In Papua New Guinea Garcinia species flower in May-July. The flowering-to-fruiting period of unidentified Garcinia trees in Peninsular Malaysia is 2-6 months. Seed dispersal is among others by orang-utans.

Garcinia includes the former genera Pentaphalangium , Septogarcinia and Tripetalum and is placed in the subfamily Clusioideae . Together with the subfamily Calophylloideae it is sometimes regarded as a distinct family: Clusiaceae . A taxonomic revision of Garcinia was in progress at the time of writing, but until it is published the status of many species remains doubtful: estimates of the total number of species range from 100 to 400.

Ecology

Wild Garcinia species are generally found scattered and are second storey trees of primary, lowland or, less often, montane rain forest, up to 900(-2100) m altitude. Some species may be encountered in secondary forest (e.g. G. hombroniana , G. parvifolia ) where they may be gregarious. Garcinia generally occurs in well-drained habitats, but e.g. G. bancana , G. maingayi , G. nigrolineata and G. parvifolia have been reported from swamp forest as well. Several species grow on limestone soils.

Silviculture Garcinia can be propagated by seed, although vegetative propagation is also used for cultivated fruit species. G. xanthochymus has about 200 seeds/kg. The seed is considered "recalcitrant" and thus sensitive to desiccation and chilling, and can only be stored for a few weeks. Many germination trials have been conducted on Garcinia species in Peninsular Malaysia. It appeared that a few species, including G. mangostana , started germinating after about 3 weeks and germination was completed about 2.5 months after sowing. In most species, however, germination did not start until after about 3 months and in some species was not completed until after 1.5 years. Usually, the germination rate is over 50% and there are indications that germination is enhanced by removing the arillode. In a 676 ha sample of rain forest in Peninsular Malaysia an average of only 2.3 Garcinia trees measuring over 40 cm in diameter per 100 ha was found. Garcinia is not fire-resistant and can stand considerable shade.

Genetic resources and breeding

It is difficult to assess the risk of genetic erosion of Garcinia as no reliable taxonomic treatment is available. Some of the species presented below have a narrow geographical distribution and may be vulnerable due to destruction of their habitat. In Songkhla, southern Thailand, 118 accessions belonging to 8 Garcinia species are maintained for their horticultural value.

Prospects

Those Garcinia species with very hard and durable wood have potential for specialty use, but very little is known of their silvicultural aspects.

Literature

40, 61, 70, 150, 151, 162, 163, 193, 209, 235, 259, 264, 267, 300, 304, 348, 396, 436, 464, 536, 543, 595, 628, 657, 668, 672, 694, 696, 704, 713, 740, 741, 770, 785, 800, 829, 831, 852, 861, 889, 934, 935, 936, 1023, 1032, 1038, 1164, 1218, 1221, 1239, 1242, 1248, 1259.

Selection of species