Millettia stuhlmannii (PROTA)
|Geographic coverage Africa|
|Geographic coverage World|
Millettia stuhlmannii Taub.
- Protologue: Engl., Pflanzenw. Ost-Afrikas C: 212 (1895).
- Family: Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
- Panga panga, partridge wood (En).
- Panga panga (Fr).
- Jambire, panga panga (Po).
- Mpangapanga, mpande (Sw).
Origin and geographic distribution
Millettia stuhlmannii is restricted to southern Tanzania, eastern Zimbabwe and Mozambique.
The wood (trade name: panga panga) is highly valued for light and heavy flooring and for furniture. It is popular in the veneer industry, where it is used for decorative furniture. It is also used for joinery, panelling, cabinet work, doors, staircases, window frames, carving, turnery and musical instruments. It is suitable for heavy construction, ship and boat building, mine props, railway sleepers, vehicle bodies, implements, toys, novelties, precision equipment, boxes and crates, but for many of these purposes it is no longer used because of its high price.
In traditional medicine a root decoction is drunk to treat stomach-ache. Poles planted during the rainy season serve as a live fence.
Production and international trade
In Mozambique Millettia stuhlmannii provides one of the most important export timbers. The volumes exported are unknown because a large part of the trade is unregistered. The main importer is China, where processed wood (mainly for flooring) is not only used domestically but also re-exported to markets in the Western World. It was estimated that 4000 m³ was traded from Zambézia province in 2004, at a price of about US$ 700/m³. Tanzania officially exported about 2000 m³ of sawn panga panga from June 2005 to January 2006, mainly to China. This represented about 45% of all hardwood sawn timber exported from the country, but the actual quantity is higher due to illegal logging. The export of unprocessed wood is prohibited in Mozambique and Tanzania, but there is still a lot of illegal export of logs.
The heartwood is dark brown or black-brown, with bands of whitish tissue giving a characteristic ‘partridge-breast’ figure on tangential surfaces; it is sharply demarcated from the pale yellow, 2.5–7.5 cm thick sapwood. The grain is straight, texture fine to medium. Abundant gum deposits are present. Logs may have brittleheart and ingrown bark.
The wood is heavy, with a density of 720–990 kg/m³ at 12% moisture content. The wood usually air-dries comparatively rapidly and without serious defects, although cracks may develop. Kiln-drying should be carried out slowly, to avoid cracking. The rates of shrinkage are from green to 12% moisture content about 1.3% radial and 2.2% tangential, and from green to oven dry 2.2–3.1% radial and 3.7–5.8% tangential. Once dry, the wood is moderately stable in service, but slightly less so than that of Millettia laurentii De Wild.
At 12% moisture content, the modulus of rupture is about 112 N/mm², modulus of elasticity 13,600 N/mm², compression parallel to grain 69 N/mm², shear 16 N/mm², cleavage 73 N/mm and Janka side hardness 7250 N.
The wood is somewhat difficult to saw and work, and sawteeth and cutting tools may blunt rapidly; stellite-tipped sawteeth and tungsten-carbide tipped cutting tools are recommended. A 15° cutting angle is recommended in planing. The wood turns well. It can be polished to a fine surface, but this should be done carefully to avoid splinters. Pre-boring before nailing and screwing is needed; the wood holds nails well. The wood can be rotary cut for veneer, but prior intensive steaming is needed. The gluing and varnishing properties are poor due to the presence of resin cells; the use of a filler improves the results considerably.
The heartwood is very durable, being resistant to fungal, dry-wood borer and termite attacks, but the sapwood is susceptible to powder-post beetle attack. The heartwood is resistant to impregnation with preservatives, the sapwood moderately resistant. The sawdust may cause dermatitis, asthma and irritation to throat, nose and eyes.
The heartwood contains robinetin, a dye-precursor for keratin-based fibres.
Adulterations and substitutes
The wood of wenge (Millettia laurentii) from Central Africa closely resembles that of Millettia stuhlmannii and is used for similar purposes. It differs in its often slightly darker colour and lack of yellowish white resin.
- Medium-sized tree up to 20(–35) m tall; bole straight or bent, cylindrical, up to 120(–150) cm in diameter; bark surface yellow or greenish grey, smooth; crown spreading; young twigs finely white hairy.
- Leaves alternate, imparipinnately compound with 2–4 pairs of leaflets; stipules oblong-spatulate, c. 1 cm long, early caducous; petiole up to 10 cm long, rachis up to 20 cm long; stipels threadlike, up to 7 mm long; petiolules up to 9 mm long; leaflets opposite, elliptical to obovate, up to 13 cm × 9 cm, rounded to notched at apex, sparsely hairy below.
- Inflorescence a terminal pendulous panicle up to 35 cm long, with branches up to 3(–9) cm long, short-hairy.
- Flowers bisexual, papilionaceous; pedicel up to 9 mm long, with 2 small bracteoles near apex; calyx campanulate, 11–13 mm long, tube c. as long as lobes; corolla pale purple, glabrous, standard orbicular, c. 25 mm in diameter, with c. 5 mm long claw at base, wings and keel c. 23 mm long; stamens 10, 9 fused, 1 free, c. 25 mm long; ovary superior, c. 10 mm long, hairy, style slender, curved, glabrous.
- Fruit an oblanceolate to linear flat pod 25–35 cm × 3.5–5 cm, with stiff wall, yellowish brown hairy but glabrescent, with lenticels, dehiscent, 6–8-seeded.
- Seeds ovoid, flattened, 20–23 mm × 17–19 mm, smooth, dark brown, with small aril at base.
Other botanical information
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.
Other Millettia species occurring in Tanzania are Millettia elongatistyla J.B.Gillett, a small tree up to 15 m tall, and Millettia sacleuxii Dunn, a small tree up to 10 m tall. Both species yield hard and heavy wood.
The wood of Millettia elongatistyla is used for building poles, tool handles and wooden spoons. It is also used as firewood and for making charcoal. The roots are used in the treatment of schistosomiasis. The tree is also suitable for shade and ornamental purposes.
The wood of Millettia sacleuxii is used for building poles, fencing, tool handles and pestles, and as firewood. Millettia sacleuxii is also suitable for amenity planting. It is classified as vulnerable in the IUCN Red list of threatened species.
Wood-anatomical description (IAWA hardwood codes):
- Growth rings: 2: growth ring boundaries indistinct or absent.
- Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; 23?: shape of alternate pits polygonal; 26: intervessel pits medium (7–10 μm); 29: vestured pits; 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 42: mean tangential diameter of vessel lumina 100–200 μm; 43: mean tangential diameter of vessel lumina ≥ 200 μm; 46: ≤ 5 vessels per square millimetre; 58: gums and other deposits in heartwood vessels.
- Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 70: fibres very thick-walled.
- Axial parenchyma: 83: axial parenchyma confluent; 85: axial parenchyma bands more than three cells wide; 89: axial parenchyma in marginal or in seemingly marginal bands; 91: two cells per parenchyma strand; 92: four (3–4) cells per parenchyma strand.
- Rays: (97: ray width 1–3 cells); (98: larger rays commonly 4- to 10-seriate); 104: all ray cells procumbent; 115: 4–12 rays per mm.
- Storied structure: 118: all rays storied; 120: axial parenchyma and/or vessel elements storied; 121: fibres storied.
- Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.
Growth and development
Millettia stuhlmannii flowers at the beginning of the rainy season, from November–January. Leaves emerge before the flowers. In the dry season trees become leafless. Millettia stuhlmannii nodulates with rhizobial bacteria.
Millettia stuhlmannii occurs in deciduous woodland up to 900 m altitude. It develops best in high-rainfall and riverine forest, and is locally dominant.
Propagation and planting
Stem cuttings planted at the onset of the rainy season usually show fair survival rates. Suckers may develop from the roots.
The tree coppices well.
A tree with a diameter of 50 cm yields about 1.9 m³ of wood, a tree with a diameter of 80 cm about 5.2 m³.
Handling after harvest
All panga panga exported legally from Tanzania and Mozambique is locally sawn before export.
Millettia stuhlmannii has a limited area of distribution, but is locally common or even dominant. However, several reports conclude that current harvest levels are too high and rapid depletion of many stands has been predicted.
Panga panga is one of the highly valued African timbers on the international market, with a still fair supply. However, there are indications that the exploitation of Millettia stuhlmannii is not carried out on a sustainable basis. Research is needed on natural regeneration and growth rates to establish criteria for sustainable production in natural forest. Using cuttings for propagation creates possibilities for the establishment of plantations. An action plan should be developed to increase local processing, optimize the market chain and to safeguard future production of this valuable timber.
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Correct citation of this article
Lemmens, R.H.M.J., 2008. Millettia stuhlmannii Taub. 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 April 2019.
- See the Prota4U database.