Prota 7(1): Timbers/Bois d’œuvre 1
U.S. Dept. Agric. Bur. Pl. Ind. Bull. 248: 55 (1912).
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Millettia caffra Meisn. (1843).
Umzimbeet, Kaffir ironwood (En). Songa (Po).
Origin and geographic distribution
Millettia grandis occurs from southern Mozambique to eastern South Africa. It has been planted occasionally outside this region, e.g. in Mauritius.
The wood is locally important for building poles, durable furniture, carving and implements such as walking sticks. It is suitable for heavy construction, heavy flooring, joinery, mine props, shipbuilding, vehicle bodies, furniture, cabinet work, implements, sporting goods, musical instruments, toys, novelties and turnery. It is valued as firewood. Millettia grandis is planted as an ornamental shade and wayside tree. It can also be used as a windbreak along pastures. Powdered seed is taken as an anthelmintic. Ground roots serve as a tranquilizer and to induce sleep. The roots have also been used as fish and arrow poison.
The heartwood is dark brown and distinctly demarcated from the yellowish sapwood. The grain is straight, texture fine. The wood has an oily surface.
The wood is very heavy and hard. The density is about 1140 kg/m³ at 12% moisture content. The wood should be dried slowly and with care to avoid serious checking. At 12% moisture content, the modulus of rupture is about 182 N/mm², modulus of elasticity 19,200 N/mm², compression parallel to grain 68 N/mm², shear 16 N/mm², Janka side hardness 15,350 N and Janka end hardness 14,100 N.
Considerable power is required in sawing and planing, but a good polish can be obtained. The wood is easy to split. It holds nails and screws well, but pre-boring is needed. It is very durable and resistant to insect attack. The heartwood does not absorb preservatives.
Evergreen or deciduous shrub or small tree up to 13(–25) m tall; bark surface smooth to flaky, grey to pale brown; twigs slightly hairy or glabrous. Leaves alternate, imparipinnately compound with 4–7 pairs of leaflets; stipules absent; petiole and rachis together 10–20 cm long; stipels needle-shaped, 4–6 mm long; petiolules c. 4 mm long; leaflets opposite, oblong to lanceolate, 4–8 cm × 1–3.5 cm, acuminate at apex, glabrous above, short-hairy below. Inflorescence a terminal, spike-like panicle up to 25 cm long, with short branches, dark brown velvety hairy. Flowers bisexual, papilionaceous; pedicel 2–6 mm long, with 2 small bracteoles near apex; calyx campanulate, c. 7 mm long, tube about as long as lobes; corolla pale purple, standard orbicular, c. 15 mm in diameter, with claw at base, wings and keel slightly shorter; stamens 10, 9 fused, 1 almost free; ovary superior, hairy, style slender, curved, hairy at base. Fruit an oblong to lanceolate, flat pod up to 15 cm × 3.5 cm, with stiff wall, densely brownish hairy, dehiscent with spiralling valves, often 2-seeded. Seeds oblong, flattened, smooth, reddish brown.
Young trees grow fairly fast: 80–100 cm/year under favourable conditions. New foliage of Millettia grandis is dark reddish brown or coppery red. Trees flower in December–January. The fruits ripen 6–8 months later. Millettia grandis nodulates with rhizobial bacteria.
Millettia comprises about 150 species, most of them (about 90) in mainland Africa, 8 endemic to Madagascar, and about 50 in tropical Asia. It is in need of revision and should be split into several genera based on molecular evidence.
Millettia grandis occurs in coastal forest and open lowland forest up to 600 m altitude. It can be found as a pioneer along forest margins. It tolerates light frost. It often occurs on sandy soils, but also on shale, where trees are often gnarled. It grows best in deep soils where ample water is available. It is locally common.
Fresh seed is used for propagation; soaking in hot water for one night improves germination. Young trees transplant well. Larvae of the butterfly Deudorix diocles are commonly found in the pods. Baboons strip off and eat the bark.
Genetic resources and breeding
Millettia grandis has a rather small area of distribution. Therefore, it may easily become liable to genetic erosion, although it is still locally common. In many regions it is already under pressure because it is a favoured tree for building poles and wood carving and because many forests in its area of distribution are being cleared for agricultural land. However, it seems that Millettia grandis could sustain current levels of exploitation in some forests in South Africa.
To meet expected demands and relieve the pressure on natural populations of Millettia grandis, starting planting programmes is recommended. These seem to have good prospects because the trees can be easily propagated by seed and grow fairly fast, so that harvesting of poles for construction and wood for the carving industry can be expected within a reasonable period. Millettia grandis also has prospects as an ornamental tree for gardens and streets and for windbreaks in agroforestry systems.
• Baloyi, K.J. & Reynolds, Y., 2004. Millettia grandis. [Internet] South African National Biodiversity Institute, Cape Town, South Africa. http://www.plantzafrica.com/ plantklm/ milletgrand.htm Accessed May 2007.
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Correct citation of this article:
Lemmens, R.H.M.J., 2008. Millettia grandis (E.Mey.) Skeels. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.