3739

5(1): Timber trees; Major commercial timbers

Pterocarpus Jacq.

Sel. stirp. amer. hist.: 283 (1763).

LEGUMINOSAE

x = probably 11; Pterocarpus indicus f. indicus: n = 10, 22; Pterocarpus indicus f. echinatus: n = 22

Trade groups Narra: medium-heavy hardwood, e.g. Pterocarpus indicus Willd.

Narra: rosewood (a general name for reddish woods used for furniture and cabinet work), amboyna, padauk, red sandalwood (En). Amboine, santal rouge (Fr). Brunei: angsana. Indonesia: sonokembang (general), angsana (Java). Malaysia: angsana (general), sena (Peninsular). Papua New Guinea: New Guinea rosewood. Philippines: apalit (general), vitali (Zamboanga). Burma: sena, padouk, ansanah. Laos: chan dêng. Thailand: pradu (general), pradu-ban (central), sano (Malay, peninsular). Vietnam: gi[as]ng h[uw][ow]ng.

This pantropical genus consists of 20 species, 5 of which occur in the Indo-Pacific region. Within the Malesian area only one species occurs naturally and is found throughout this area. Most species are found in western tropical Africa (11). If one considers the centre of origin of a genus to be located at the place with the highest species diversity, western tropical Africa can be considered as such.

Narra is used as a structural timber for light to heavy construction, joists, rafters, beams and interior finish. The wood being generally reddish and figured is ranked among the finest for furniture, panelling, musical instruments, high-grade cabinet work, high-class interior joinery, billiard tables, decorative flooring for both light and heavy traffic, agricultural implements, high-class vehicle bodies, cart and gun carriages, oil presses, tool handles, carvings and novelties. A high-grade figured veneer can be sliced from the wood for the outer layers of plywood and cabinet work. Due to its low shrinkage and movement narra is suitable for precision instruments. Its inherent strength to withstand weathering, wearing and insect attacks makes it useful for purposes such as bridges, piles, posts, railway sleepers, shafts and mine timber, although treatment with a preservative is recommended. Because of its comparatively good resistance to marine borer attack it is considered to be suitable for marine construction works as a substitute for teak. In some areas narra is considered the best material for canoes. Physiologically diseased trees, which are found most commonly on Seram, yield a famous strongly figured material known as 'Ambonese gnarl wood' or 'amboyna'.
The bark exudes a gummy or resinous substance which is called 'kino' or 'sangre de drago' (dragon's blood). It is a powerful astringent and the boiled, shredded bark is used against diarrhoea and dysentery. It is sometimes used as a diuretic but its diuretic properties have not yet been clearly demonstrated. The bark also has tanning properties and it dyes a reddish or yellowish colour (e.g. Pterocarpus indicus, Pterocarpus macrocarpus Kurz and Pterocarpus santalinoides L'Hérit. ex DC.). The wood yields a dye giving a brown or brick-red colour. The colour of the dye is, however, less intense than that of the well-known Indian Pterocarpus santalinus L.f. Pterocarpus indicus is extensively cultivated as an ornamental or shade tree, especially in Peninsular Malaysia, Singapore, Indonesia and the Philippines. It is recommended for planting in denuded areas and brushland to stabilize the soil; it may improve the soil by nitrogen fixation. The flowers and very young leaves are sometimes eaten.

Narra is particularly important in the Philippines, Papua New Guinea and Thailand. In the Philippines the total export of narra wood in 1985 was 3 million kg (40% processed) with a value of US$ 1.1 million. The export declined to 2.3 million kg in 1986 (57% processed) with a value of US$ 935 000, and to 430 000 kg (all processed) with a value of US$ 220 000 in 1987. From then on, the export was negligible and at present there is a total ban on cutting narra trees.
In Papua New Guinea it is an important timber which fetches very high prices; the export of logs is banned, and only processed wood is exported.
Thailand exported 5.8 million kg of sawn Pterocarpus (Pterocarpus indicus and Pterocarpus macrocarpus) timber in 1990, worth US$ 10.3 million. However, Thailand also imports this timber, in 1990 to an amount of 11 000 m³ (non-processed) with a value of US$ 1.9 million, mainly from Burma but also in small amounts from Laos, Cambodia and Vietnam.

Narra is a medium-weight, moderately hard to hard, tough and resilient wood. The heartwood is light yellowish-brown to reddish-brown with darker irregular streaks; it is distinctly demarcated from the generally pale straw-coloured to light grey sapwood. The density is (390—)550—900(—940) kg/m³ at 15% moisture content. The grain of the wood is interlocked or wavy, texture moderately fine to moderately coarse.
At 12% moisture content the modulus of rupture is 86—96 N/mm², modulus of elasticity 11 100—12 300 N/mm², compression parallel to grain 55—62 N/mm², compression perpendicular to grain 8—9 N/mm², shear 10—13 N/mm², cleavage c. 56 N/mm radial and 45 N/mm tangential, Janka side hardness 3870—7200 N and Janka end hardness 4540—6900 N.
The rates of shrinkage are low to moderate, from green to 15% moisture content 0.5—1.0% radial and 1.0—1.3% tangential, and from green to oven dry 2.8—3.3% radial and 4.0—5.9% tangential. Narra is generally easy to season with little or no degrade. Once dry, the wood is very stable in service.
Generally the wood is easy to work and does not blunt sawteeth and edges for a considerable time, because it contains very little or no silica. The presence of interlocked grain may result in picking up of grain on radial surfaces during planing. Narra wood turns and chisels very well, and gluing, sanding and polishing give no problems. It nails and screws well and pre-boring is not required; only very thin boards tend to split slightly when nailed. Narra receives paints and varnishes well, but for some material, fillers are needed. It can be peeled very satisfactorily without prior treatments, to produce very decorative veneer.
The figures on durability of narra wood differ considerably, probably because of the wide variation of density of tested wood. Narra is generally rated as durable; this was shown, for instance, in tests of wood from Indonesia, the Philippines and Papua New Guinea, where a service life in contact with the ground of up to 20 years is reported. A test in Malaysia, however, resulted in a classification of the wood as non-durable, with a maximum service life of 2 years. The heartwood is usually resistant to termites, but the sapwood is susceptible to attack by powder-post beetles. Narra is extremely durable when used for interior work in the tropics and subtropics. The heartwood is resistant to preservative impregnation, but the sapwood is permeable. Fresh and dry sawdust may produce an aromatic odour, and may irritate nose and throat.
Wood of Pterocarpus indicus contains 49% cellulose, 24% lignin, 11% pentosan, 0.9% ash and up to 0.3% silica. The solubility is 2.2% in alcohol-benzene, 0.4% in cold water, 4.1% in hot water and 16.2% in a 1% NaOH solution. The energy value is 20 150 kJ/kg. Narra wood contains santalin, a red crystalline compound which constitutes the main colouring matter. The polyphenolic substance isolated from the bark of Pterocarpus indicus inhibits the esterolytic activity of plasmin, and shows carcinostatic activity in mice.

Small to large, generally deciduous trees up to 40 m tall; bole often of poor form, strongly fluted and gnarled and up to 350 cm in diameter, with numerous, plank-like buttresses; bark surface finely scaly fissured, finely streaked cream and brown, inner bark thin, producing red sap when cut; crown dense, domed; branchlets often lenticelled; indumentum of simple, usually short and adpressed hairs. Leaves alternate, imparipinnate; stipules generally small, linear or narrowly triangular, usually early caducous; leaflets alternate or sometimes subopposite, entire. Inflorescence axillary or terminal, racemose or paniculate; bracts and bracteoles small, linear to narrowly triangular. Flowers bisexual, irregular; calyx turbinate to campanulate, 5-lobed, the upper two lobes usually larger, sometimes united; petals 5, free, clawed, generally yellow, glabrous or sparsely hairy outside, standard obovate to spatulate, keels shorter than the wings and connate at base; stamens 10, upper stamen free or joined to the staminal sheath, anthers dorsifixed, versatile, dehiscing lengthwise; ovary usually stipitate, with 2—8 ovules and 1 style with a terminal, minute stigma. Fruit a compressed, indehiscent pod, disk-like or sometimes falcate, broadly winged or rarely slightly keeled, with a thickened central, usually woody or corky seed-bearing portion, with 1—3(—4) seeds. Seed kidney-shaped to oblong, usually narrowed and curved near the minute hilum, smooth to undulate, testa brown to blackish, aril minute. Seedling with epigeal germination; the cotyledons borne at or above the soil level; first 2 or 3 leaves simple, arranged spirally, subsequent ones compound and alternate.

— Macroscopic characters:
Heartwood light yellowish-brown to reddish-brown and distinctly demarcated from the straw-coloured to light grey sapwood. Grain wavy or interlocked. Texture moderately fine to moderately coarse; ribbon figure present on quarter-sawn faces, zigzag figure present in material with wavy grain; wood not very glossy. Growth rings distinct, formed by concentric alignment of large pore rings and by a layer of darker coloured wood at the end of the ring (ring-porous); vessels visible to the naked eye, particularly distinct at the base of the large pore rings, solitary and in radial multiples of 2—4, tyloses present; axial parenchyma distinct to the naked eye, aliform, in concentric confluent layers and terminal, confluent parenchyma irregularly and closely spaced and wavy; rays barely visible to the naked eye on cross-section but visible to the naked eye on the tangential face because of the storied arrangement (ripple marks).
— Microscopic characters:
Growth rings distinct, marked by concentric alignment of large pore rings. Vessels very few to few, 1—3(—6)/mm², about 68% solitary, 28% in radial multiples of 2—4, and 4% in clusters, very small in the latewood to very large in the earlywood, 45—375 µm in tangential diameter, mostly medium-sized to moderately large (135—230 µm), vessel elements very short to medium-sized (predominantly 225—360 µm); perforation plates simple; intervessel pits alternate, small, vestured; vessel-ray pits similar to intervessel pits; tyloses occasionally present. Fibres predominantly medium-sized to moderately long (average length 1.3 mm), non-septate, thin-walled, with numerous simple pits with slit-like apertures in the radial walls. Axial parenchyma abundant, aliform-confluent or in irregular confluent bands, and terminal, strands usually 2-celled or parenchyma cells fusiform. Rays 6—10/mm, 1(—2)-seriate, 2—12 cells high, mostly 5—9 cells wide, extremely fine to moderately fine (11—33 µm wide), homocellular and composed of procumbent cells. Rhomboidal crystals present in chambered axial parenchyma cells, 2—8 (or more) in a strand. Axial parenchyma strands and rays distinctly storied.
Species studied: Pterocarpus indicus.

After germination, the cotyledons are exposed above the soil on a long hypocotyl and the seed-coat is left in or on the soil, usually in the indehiscent pod. Root growth of narra is very extensive and characterized by anastomosing laterals. Pterocarpus indicus is a fairly fast grower; trees are reported to reach a maximum diameter of 58 cm in 40 years. Pterocarpus dalbergioides trees may attain 8 m in height and a diameter of 5.5 cm in 4 years, 14 m in height and 11.5 cm in diameter in 8 years, and 25 m in height in 12 years.
Narra is a deciduous tree, often 'semi-deciduous' (i.e. some trees do not completely lose their leaves). The leaves fall off during the dry season, usually 2—3 months after the end of the rainy season. New leaves develop simultaneously with the flowers, but sometimes young leaves develop fully before flowering begins. Not all flowers in a panicle or raceme open simultaneously. The flowers in the lower portion of the inflorescence open first and later wither, losing their petals which often carpet the ground beneath the tree. After a short period, when the subsequent flowers in the upper portion of the inflorescence open and blossom, there is a second fall of petals, although not as profuse as before. In areas with no distinct wet and dry seasons (e.g. in Singapore), gregarious flowering does not occur frequently, and instead, flowering is asynchronous.
Fruits are mature 3—4 months after flowering. They are dispersed over short distances by wind, and over long distances by water and sometimes by sea currents.

The genus Pterocarpus belongs to the tribe Dalbergieae. Its closest relatives are believed to be the South American genera Tipuana and Fissicalyx. The different species of Pterocarpus are generally recognized by characters of the fruit (size, width of the wing, and position of the style remnant) and sometimes that of the flower (presence of bracts and bracteoles, hairiness of pedicel, calyx and ovary, number of ovules). Vegetative characters can only be used with any reliability on a local scale.
In addition to Pterocarpus indicus and Pterocarpus dalbergioides, the wood of several other Pterocarpus species from outside Malesia is highly appreciated, e.g. Pterocarpus macrocarpus in Burma, Thailand and Indo-China, Pterocarpus santalinus and P. marsupium Roxb. in India, and Pterocarpus soyauxii Taub. in Africa.

Narra prefers a slightly seasonal climate but is found in both evergreen and semi-deciduous forest. Its natural habitat is riparian along banks of rivers and coastal tidal creeks and rocky shores but it is highly adaptable to other environmental conditions. When planted, narra is able to grow in a wide range of habitats and soil conditions, for example in flat sandy areas, in hilly areas with a heavy clay soil but also in waterlogged areas. Pterocarpus indicus thrives best on moist sandy loam or clay-loam soil. Narra is a nitrogen-fixing tree and demands light. In natural conditions narra is often an element of the upper storey of the forest canopy and is sometimes found as a dominant tree together with molave (Vitex parviflora Juss.) in the Philippines. In Papua New Guinea Pterocarpus indicus is particularly common as a canopy tree in valleys below 100 m altitude, together with Kingiodendron alternifolium (Elm.) Merr. & Rolfe.

Narra is easily propagated by seed. The weight of 1000 seeds is about 770 g. Germination rate is improved if seeds are extracted from the indehiscent pods before sowing. Seeds are sown in nursery beds, and the seedlings are potted in plastic bags when one month old; at an age of 4—6 months (average height 20—25 cm) they are ready for planting into the field. Since the percentage of viable seeds is often low (sometimes as low as 10—20%) and the survival ability of young seedlings is vulnerable to weed competition, vegetative propagation has become a more important technique nowadays.
Stump cuttings, taken from seedlings or wildlings, can be used as planting material. The recommended stem length is 10—20 cm, root length 20—40 cm and stem diameter 1.5—2 cm. Shoot cuttings of 10 cm in diameter and 2 m in length are used in the Philippines. Treatment with growth hormones enhances root formation. Cuttings were established successfully in 80% of the cases studied in Indonesia.
Narra can also be propagated successfully by tissue culture. Tissue taken from 0.5—3-year-old shoots placed on a growing medium produces callus within 7—12 days. After 21—48 days, root differentation occurs. Irradiation induces dormant buds to develop in tissue culture.
In plantations of Pterocarpus indicus normal spacing is 2.5 m 2.5 m or 3 m 3 m. The recommended spacing for Pterocarpus dalbergioides is 1.5 m 1.5 m or 2 m 2 m.

No information is available about the proper management of narra in natural stands. The trees often occur scattered in dipterocarp forest where the cutting is governed by diameter limits (usually 60 cm). However, as narra wood is in great demand for top-class furniture, trees of less than 60 cm diameter are sometimes cut illegally, particularly in the Philippines.
Plantations of narra (and particularly of Pterocarpus dalbergioides) have a reputation to be labour-intensive, requiring much tending such as close initial spacing and regular thinning. This is because of the tendency of the trees to fork and form very short boles.

In nurseries in the Philippines, an anthracnose seedling disease caused by Colletotrichum sp. has been reported, which leads to brownish spots on leaves and stems and subsequent wilting. Fungi such as Fomes lamaoensis and Ganoderma lucidum may cause root and stem rot. Phomopsis sp. (also a fungus) may infest seeds. A plantation of Pterocarpus indicus in southern Sumatra has been severely attacked by a caterpillar (Melipotis diversipennis). In Peninsular Malaysia many trees were attacked and killed late last century by an unknown disease with symptoms resembling those of the Dutch Elm disease in Europe. Narra is susceptible to infestation by parasites such as Loranthus sp. and strangling figs (e.g. Ficus retusa L.).

Large narra trees are often hollow.

Narra trees in a 60-year-old plantation in Malaysia yielded slightly more than 1 m³/tree, having an average bole diameter of 49 cm and branchless bole length of 7.1 m. The fact that the trees are usually short-boled with big branches limits the yield.
For maximum timber production of Pterocarpus dalbergioides in the Andaman Islands, the rotation is 25—30 years, while the annual production is 6.5 m³/ha. The total timber volume in a stand of 500 trees/ha after 32 years is reported as 200 m³/ha. In a natural forest in Seram (the Moluccas) the average standing stock of Pterocarpus indicus was assessed at 6—10 trees/ha.

The native stands of narra are disappearing quickly. The demand for luxury woods such as narra often far exceeds the supply; this easily leads to illegal cutting. Pterocarpus indicus is now probably extinct in Peninsular Malaysia because of overexploiting of its few known stands. Shifting cultivation is another cause of genetic erosion. Narra often grows along rivers, and these sites are often the first to be settled by shifting cultivators. Narra is slightly secured against extinction, because it has a large area of distribution and is often planted, for instance, as a roadside tree.

The establishment of plantations of narra can help to prevent genetic erosion and will also supply high-quality timber in the future. Plantations can already be harvested at 60 years or even less in favourable sites. Moreover, narra is easy to propagate and plant.

Ang, L.H., 1988. A note on the growth of Pterocarpus indicus in a sixty-year old plantation in Malaysia. Journal of Tropical Forest Science 1: 188-189.
Burgess, P.F., 1966. Timbers of Sabah. Sabah Forest Records No 6. Forest Department, Sabah, Sandakan. pp. 371-375.
Cadiz, R.T. & Mizal, R.B., 1989. Narra (Pterocarpus indicus). Rise (Research Information on Ecosystems) 1(2): 47-63.
Dalmacio, M.V., Crisaldo, E.N. & Genil, Z., 1978. Production of 'instant trees'. I. Narra. Sylvatrop Philippine Forest Research Journal 3: 54-55.
Lamprecht, H., 1989. Silviculture in the tropics. Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), Eschborn. pp. 302-303.
Manuputty, D.N., 1973. Pterocarpus indicus in the island of Ceram, Moluccas. Rimba Indonesia 17: 169-175.
Martawijaya, A., Kartasujana, I., Kadir, K. & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 137-141.
Rojo, J.P., 1972. Pterocarpus (Leguminosae - Papilionaceae) revised for the world. Phanerogamarum Monographiae, Vol. 5. J. Cramer, Lehre. 119 pp.
Sim, H.C., 1988. Malaysian timbers - sena. Timber Trade Leaflet No 108. Malaysian Timber Industry Board, Forest Research Institute Malaysia. 5 pp.
Wong, Y.K., 1982. Horticultural notes on the angsana (Pterocarpus indicus Willd.). Gardens Bulletin, Singapore 34: 189-202.

J.P. Rojo (general part, wood anatomy, selection of species) & D.S. Alonzo (properties)

Pterocarpus dalbergioides
Pterocarpus indicus

Rojo, J.P. & Alonzo, D.S., 1993. Pterocarpus Jacq.. In: Soerianegara, I. and Lemmens, R.H.M.J. (Editors): Plant Resources of South-East Asia No 5(1): Timber trees; Major commercial timbers. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea

The following species in this genus are important in this commodity group and are treated separatedly in this database:
Pterocarpus dalbergioides
Pterocarpus indicus