Prota 2: Vegetables/Légumes
Notizbl. Bot. Gart. Berlin 8: 152 (1922).
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Padouk blanc (Fr). Mkula (Sw).
Origin and geographic distribution
Pterocarpus mildbraedii is found in Sierra Leone, Liberia, Côte d’Ivoire, Ghana, Benin, Nigeria, Cameroon, Equatorial Guinea, Gabon and the Usambara and Udzungwe Mountains (Tanzania). Records for DR Congo are based on misidentification.
The leaves of Pterocarpus mildbraedii are used as a cooked vegetable in Nigeria. In Ghana the trees have been planted or retained in cocoa plantations to provide shade. Pterocarpus mildbraedii is rarely exploited for its timber, e.g. in Tanzania, and the wood is used to make mortars.
The leaves of Pterocarpus mildbraedii contain per 100 g edible portion: water 85 g, energy 237 kJ (57 kcal), protein 3.8 g, fat 0.8 g, carbohydrate 8.2 g, crude fibre 1.13 g, Ca 72 mg, Mg 28 mg, Fe 4.7 mg and Zn 3.1 mg (Akpanyung, E.O., Udoh, A.P. & Akpan, E.J., 1995). Hydrogen cyanide and oxalate levels are high but not such that they pose a health danger for consumers. An ethanolic extract proved toxic to rats only after intraperitoneal administration. The wood is whitish and soft, and of little commercial value.
Medium-sized to large tree up to 35 m tall, with smooth, grey or pale brown bark, exuding red gum when cut, and small, rounded crown. Leaves alternate, imparipinnate, up to 35 cm long; stipules lanceolate, up to 1 cm long, caducous; leaflets (5–)7–15, alternate, elliptical -oblong to ovate, 6–14 cm × 3–7 cm, base rounded to cuneate, apex abruptly acuminate. Inflorescence a raceme or little-branched panicle 5–15 cm long. Flowers bisexual, papilionaceous, 5-merous; calyx 5–8 mm long, densely covered with short hairs on the lobes inside and near lobe margins outside; corolla golden-yellow, 1–1.5 cm long. Fruit an obovate-orbicular pod 10–12 cm long, with very broad membranous wing, style base lateral, 1(–2) -seeded.
Pterocarpus comprises about 60 species, 20 of them in Africa. Several Asian and African species are commercial timbers. Pterocarpus santanalioides DC., Pterocarpus soyauxii Taub. and Pterocarpus osun Craib, all primarily used for timber, have leaves that are used as vegetable as well.
The two disjunct populations of Pterocarpus mildbraedii in West-Central Africa and East Africa are sometimes considered as subspecies: subsp. mildbraedii and subsp. usambarensis (Verdc.) Polhill, respectively. They differ in the size of bracts and flowers.
Pterocarpus mildbraedii grows fast and coppices well. Its root system is superficial: most roots are in the top 30 cm of the soil. It has an intermittent pattern of leaf flushes. Flushes appear in the dry season when other leafy vegetables are scarce.
Pterocarpus mildbraedii occurs in lowland rainforest, dry evergreen forest and riverine forest, up to 1250 m altitude. In Tanzania it is restricted to altitudes of 300–600 m. It is tolerant of acid soil.
Pterocarpus mildbraedii leaves are collected from the wild, but frequently marketed. Attempts to domesticate it are being made. Propagation can be done by seed, budding or cuttings.
Genetic resources and breeding
In West and Central Africa Pterocarpus mildbraedii is widespread, although in some countries recorded as rare (e.g. in Ghana), and does not seem to be liable to genetic erosion. However, the populations in Tanzania are of limited extent and vulnerable.
Pterocarpus mildbraedii is a nutritious vegetable but despite this is only exploited as such in southern Nigeria. A better understanding of the variation in the species might help in the process of domestication. It is being tested in agroforestry systems.
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Correct citation of this article:
Bosch, C.H., 2004. Pterocarpus mildbraedii Harms In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.