Pterocarpus rotundifolius (PROTA)

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Pterocarpus rotundifolius (Sond.) Druce


Protologue: Rep. Bot. Soc. Exch. Club Brit. Isles 1916: 642 (1917).
Family: Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Chromosome number: 2n = 24

Vernacular names

  • Round-leaved bloodwood, round-leaved teak (En).

Origin and geographic distribution

Pterocarpus rotundifolius is widely distributed from Angola, DR Congo and Tanzania south to northern Namibia, Botswana, Mozambique, northern South Africa and Swaziland.

Uses

The wood is locally used for furniture, shelves, picture frames, household utensils, wagon wheels and axe handles. It is also used as firewood. In Zimbabwe sap from the tree is used as eye drops to treat eye complaints and in Tanzania a root decoction is drunk to treat anaemia. The foliage is browsed by cattle. The flowers are a good source of nectar for honeybees. The tree is occasionally planted as ornamental and for erosion control.

Properties

The bole is often poorly shaped. The heartwood is creamy white and has an offensive, irritating smell when freshly cut. It is moderately heavy to heavy, with a density of 650–850 kg/m³ at 12% moisture content. The wood is rather difficult to saw, but it works well. It is moderately durable and fairly resistant to insect attack. The seed contains 12% oil, the main fatty acids being linoleic acid, palmitic acid, oleic acid and stearic acid.

Description

  • Deciduous shrub or small to medium-sized tree up to 20 m tall, but usually much smaller, often many-stemmed; bole up to 60 cm in diameter; bark surface pale grey to brown, reticulately fissured or scaly, inner bark exuding a reddish gum on slashing; crown rounded, irregular; twigs short-hairy when young, glabrescent.
  • Leaves alternate, imparipinnately compound with 3–19 leaflets; stipules linear, up to 15 mm long, falling off early; petiole 2–6(–8.5) cm long, rachis (2–)8–23(–30) cm long, densely hairy, glabrescent; petiolules (2–)5–15(–24) mm long; leaflets alternate to opposite, almost orbicular to ovate or elliptical, (3–)4.5–10(–15) cm × 2.5–6(–11) cm, base cuneate to rounded, apex shortly acuminate to rounded or notched, papery to thinly leathery, appressed hairy below when young but later often glabrescent, with 8–14 pairs of lateral veins.
  • Inflorescence a laxly branched, terminal panicle 8–40 cm long, hairy.
  • Flowers bisexual, papilionaceous; pedicel 3–10(–12) mm long; calyx campanulate, 6–9 mm long, usually glabrous, with 5 triangular teeth 2–5 mm long, upper 2 teeth longer than lower 3; corolla with clawed petals, yellow or orange-yellow, standard broadly obovate to almost circular, up to 17 mm × 16 mm, wings up to 16 mm long, keel up to 13 mm long; stamens 10, fused into a sheath up to 10 mm long, the upper stamen sometimes partly free; ovary superior, 1-celled, stiped, hairy, style up to 3 mm long, glabrous.
  • Fruit an elliptical-oblong to almost orbicular, flattened, indehiscent pod 4–6.5 cm long, on a stipe up to 1 cm long and with a thinly leathery wing, glabrous or slightly hairy, brown, 1(–2)-seeded.
  • Seed c. 6–9 mm × 4–5 mm, smooth, dark brown to blackish.

Other botanical information

Seedlings grow fairly fast and may reach 1 m tall after one year. In southern Africa Pterocarpus rotundifolius trees are often completely leafless from June to October. They usually flower in the rainy season, but during hot and dry weather the flower buds remain closed. Flowering is often very profuse. The strongly fragrant flowers last 2–3 days and are commonly visited by bees, which probably act as pollinators. Fruits take about 3 months to mature. They are dispersed by wind. The roots have nodules containing nitrogen-fixing bacteria.

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. Three subspecies of Pterocarpus rotundifolius are distinguished: subsp. rotundifolius, subsp. martinii (Dunkley) Lock (synonym: Pterocarpus martinii Dunkley) and subsp. polyanthus (Harms) Mendonça & Sousa (synonym: Pterocarpus polyanthus Harms). Intermediate specimens are rather common.

Ecology

Pterocarpus rotundifolius occurs in woodland and wooded grassland up to 900 m altitude. In a study in South Africa, it preferred clayey, medium-leached, acid, non-sodic soils with low conductivity, but in many areas it is common on deep sandy soils. In Mozambique Pterocarpus rotundifolius was found to be fire-tolerant.

Management

Seeds are often infested by insects; infested seeds should be removed before sowing. Soaking the seed in water for one night improves the germination rate. It is recommended that sowing be done in a mixture of sand and sieved compost (2:1), and seedlings with one leaf should be transplanted in planting bags filled with a sand-based, well-drained growth medium. Care should be taken to avoid damage to the taproot. Seedlings need to be protected from frost until about 2.5 m tall. Large stem cuttings (2–3 m long and about 10 cm in diameter) planted in holes filled with sand have been used for propagation; they showed a high survival rate. Trees can be managed by coppicing.

Genetic resources

There is no reason to consider this widespread and locally common tree as threatened, although in some regions the trees are heavily browsed by cattle and elephants.

Prospects

Pterocarpus rotundifolius is of limited importance as a timber tree because of its often poorly shaped and small-sized bole. However, it is a multipurpose tree, important for forage and firewood, as well as for apiculture. It deserves more attention as an ornamental tree and has good prospects for soil conservation and improvement.

Major references

  • Coates Palgrave, O.H., 1957. Trees of Central Africa. National Publications Trust, Rhodesia and Nyasaland, Salisbury, Southern Rhodesia. 466 pp.
  • Mutshinyalo, T., 2003. Pterocarpus rotundifolius (Sond.) Druce. [Internet] South African National Biodiversity Institute, Cape Town, South Africa. http://www.plantzafrica.com/ plantnop/pterocarprotund.htm July 2007.
  • Palmer, E. & Pitman, N., 1972–1974. Trees of southern Africa, covering all known indigenous species in the Republic of South Africa, South-West Africa, Botswana, Lesotho and Swaziland. 3 volumes. Balkema, Cape Town, South Africa. 2235 pp.
  • Rojo, J.P., 1972. Pterocarpus (Leguminosae-Papilionaceae) revised for the world. Phanerogamarum Monographiae. Volume 5. J. Cramer, Lehre, Germany. 119 pp.
  • World Agroforestry Centre, undated. Agroforestree Database. [Internet] World Agroforestry Centre (ICRAF), Nairobi, Kenya. http://www.worldagroforestry.org/ Sites/TreeDBS/ aft.asp. June 2007.

Other references

  • Bredenkamp, G.J., 1986. Ecological profiles of potential bush encroacher species in the Manyeleti Game Reserve, Transvaal, South Africa. South African Journal of Botany 52(1): 53–59.
  • Coates Palgrave, K., 1983. Trees of southern Africa. 2nd Edition. Struik Publishers, Cape Town, South Africa. 959 pp.
  • Gelfand, M., Mavi, S., Drummond, R.B. & Ndemera, B., 1985. The traditional medical practitioner in Zimbabwe: his principles of practice and pharmacopoeia. Mambo Press, Gweru, Zimbabwe. 411 pp.
  • Gunstone, F.D., Taylor, G.M., Cornelius, J.A. & Hammonds, T.W., 1968. New tropical seed oils. II. Component acids of leguminous and other seed oils. Journal of the Science of Food and Agriculture 19(12): 706–709.
  • Lock, J.M., 1999. A change in status for a southern African Pterocarpus (Leguminosae: Papilionoideae). Kew Bulletin 54(1): 208.
  • Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
  • van Wyk, B.E. & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza Publications, Pretoria, South Africa. 351 pp.
  • van Wyk, B. & van Wyk, P., 1997. Field guide to trees of southern Africa. Struik Publishers, Cape Town, South Africa. 536 pp.
  • Williamson, J., 1955. Useful plants of Nyasaland. The Government Printer, Zomba, Nyasaland. 168 pp.
  • Zolho, R., 2005. Effect of fire frequency on the regeneration of miombo woodland in Nhambita, Mozambique. [Internet] MSc thesis, University of Edinburgh, United Kingdom. 71 pp. http://www.miombo.org.uk/ RZMSc.pdf. April 2008.

Author(s)

  • R.H.M.J. Lemmens, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Lemmens, R.H.M.J., 2008. Pterocarpus rotundifolius (Sond.) Druce. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 10 August 2021.