Prota 7(1): Timbers/Bois duvre 1
Prodr. 2: 419 (1825).
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
n = 9, 2n = 22
Origin and geographic distribution
Pterocarpus santalinoides occurs from Senegal east to the Central African Republic and DR Congo, and is also widespread in South America.
The wood is locally used for temporary construction, carpentry, sculpturing, fences and boxboard. It is also used as firewood.
Roasted seeds are edible, tasting slightly like groundnut, but raw seeds are toxic. Cooked young leaves are eaten as a vegetable; they are also added to soup. The foliage is an important forage for many kinds of livestock. The bark is locally used for dyeing textiles brownish, while the bark. exudate is occasionally used to give them a reddish colour. Pterocarpus santalinoides is occasionally planted as a shade tree for crops and to improve the soil by fixing nitrogen and litter production. It is also planted as a windbreak. The bark, roots and leaves are commonly used in medicinal preparations. Decoctions are administered externally to wounds to promote healing, and to treat haemorrhoids and fever. They are taken internally to treat bronchial complaints, amoebic dysentery, stomach-ache and sleeping sickness, to prevent abortion and ease childbirth, and as a tonic.
The heartwood is creamy white to yellowish and indistinctly demarcated from the sapwood. The texture is moderately fine. The wood is moderately lightweight, moderately soft and easy to work. It is not durable and is liable to attacks by fungi and borers.
Tannin is present in the bark and the wood. Stem extracts showed slight antimalarial activity against Plasmodium falciparum strains. The fat content of the seeds is low: less than 1%. In tests with West-African dwarf goats fed with Pterocarpus santalinoides foliage, weight gains were low, only about 8.5 g/day. The litter production is relatively low: in tests in southern Nigeria 7.38.1 t/ha.
Usually evergreen small tree up to 15 m tall; bole usually short, straight or more or less twisted, up to 50 cm in diameter; bark thin, bark surface greyish brown, scaly and flaking in small patches, inner bark yellowish white to pinkish with red stripes, exuding a little reddish gum on slashing; crown dense, with more or less drooping branches; twigs glabrous, with lenticels. Leaves alternate, imparipinnately compound with (5)68(9) leaflets; stipules often curved, up to 2(3) cm long, slightly hairy; petiole (2)34(5.5) cm long, rachis (4.5)811(15.5) cm long, sparsely hairy, glabrescent; petiolules 25 mm long; leaflets alternate to almost opposite, ovate to elliptical, (4)6.512(14.5) cm ื (2)35.5(7) cm, base rounded to obtuse, apex shortly acuminate, papery to thinly leathery, sparsely hairy below when young but soon glabrescent, with 710(15) pairs of lateral veins. Inflorescence an axillary raceme (4)614(20) cm long, short-hairy. Flowers bisexual, papilionaceous; pedicel 24(5) mm long; calyx campanulate, 8.59.5 mm long, densely brownish hairy, with 5 triangular teeth 1.52.5 mm long, lower 3 teeth smaller than upper 2; corolla with clawed petals, bright yellow to orange-yellow, standard almost circular, up to 13 mm ื 15.5 mm, wings up to 15 mm long, keel up to 12 mm long; stamens 10, fused into a sheath up to 10 mm long, the upper stamen sometimes partially free; ovary superior, whitish hairy, style up to 11.5 mm long, glabrous towards the top. Fruit an almost orbicular, flattened, indehiscent pod 2.54.5(6) cm in diameter, wrinkled or warty, brownish hairy, beige to pale brown, with a keel-like wing, 1(2)-seeded. Seed kidney-shaped, 1.52 cm ื c. 1 cm, dark brown.
Pterocarpus santalinoides grows fast. In trials in southern Cameroon the fastest growing trees reached a height of 6.4 m and a diameter of 10.3 cm 20 months after planting. Trees flower towards the end of the dry season. Bees commonly visit the flowers and probably act as pollinators. Fruits mature 23 months after flowering in the rainy season. They float in water. The roots have nodules containing nitrogen-fixing bacteria, but in tests in south-eastern Nigeria nodules did not develop in seedlings.
Pterocarpus is a pantropical genus belonging to the tribe Dalbergieae; it comprises approximately 30 species of which about 15 occur in Africa, 10 in America and 5 in Asia.
Pterocarpus santalinoides is typically found on river banks, usually on sandy and moist soils, up to 500 m altitude. It occurs in regions with an annual rainfall of about 1600 mm, and may survive dry periods of over 5 months provided that the roots can reach the ground water. It tolerates shade and seasonal waterlogging. It is locally common, and sometimes even occurs gregariously. In central C๔te dIvoire about 60 adult trees per km have been recorded along the Bandama river. In southern Cameroon planted trees performed well on highly acidic and aluminium toxic soils.
Pterocarpus santalinoides can be propagated by seeds, stem cuttings and root cuttings. Dry seeds can be stored for longer periods. Scarification or soaking in water is recommended prior to sowing. Germination starts after 714 days, and the germination rate is about 70%. Trees can be managed by pollarding, coppicing and lopping.
Tests in Nigeria and Cameroon showed that Pterocarpus santalinoides has significant potential for alley cropping. Hedgerows were established using 2-month-old seedlings planted at 4 m ื 0.25 m. The hedgerows were pruned after one year at 50 cm height, in subsequent years twice a year, and interplanted with maize.
Fruits are often collected from the water surface. They are heated over a fire until the seeds appear, which are eaten roasted.
Pterocarpus santalinoides is a host plant for the bean pod borer Maruca vitrata, which is a pest of e.g. cowpea; it is a key relay host during the long dry season.
Genetic resources and breeding
There are no indications yet that Pterocarpus santalinoides is threatened by genetic erosion. However, its characteristic habitat, i.e. riparian forests, is under pressure in many regions because of transformation into agricultural land, especially for rice cultivation.
Like several other Pterocarpus species, Pterocarpus santalinoides is a multipurpose tree that deserves more attention. It will not gain importance as a timber tree because it is too small and provides wood of moderate quality, but it has prospects for agroforestry programmes as it improves soil fertility and outcompetes weeds, as well as providing forage and fuelwood. It is an important species for soil conservation in water catchment areas. Moreover, Pterocarpus santalinoides is suitable as an ornamental tree, having showy flowers and shiny leaves.
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Correct citation of this article:
Lemmens, R.H.M.J., 2008. Pterocarpus santalinoides DC. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois duvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
obtained from P. Ekpe NSBP
part of flowering branch
obtained from P. Ekpe NSBP
various parts of the tree
obtained from The Virtual Field Herbarium
wood in transverse section
wood in tangential section