Bobgunnia fistuloides (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Medicinal
Timber
Fuel
Conservation status

distribution in Africa (wild)

1, base of bole; 2, part of flowering twig; 3, fruit. Redrawn and adapted by G.W.E. van den Berg

base of bole

bark

slash

fruits

wood in transverse section

wood in tangential section

wood in radial section

Bobgunnia fistuloides (Harms) J.H.Kirkbr. & Wiersema

Protologue: Brittonia 49(1): 3 (1997).

Family: Caesalpiniaceae (Leguminosae - Caesalpinioideae)

Chromosome number: 2n = 16

• Swartzia fistuloides Harms (1910).

Bobgunnia fistuloides occurs in Côte d’Ivoire and Ghana and from Nigeria and Cameroon southward to Cabinda (Angola).

The wood of Bobgunnia fistuloides, named ‘pau rosa’ or ‘boto’ in trade, is traditionally used for house posts, percussion instruments, mortars, pestles and carvings. It is also used for cabinet work and for barrels and containers for acid products. It is suitable for heavy flooring, interior trim, mine props, ship building, furniture, sporting goods, toys, novelties, musical instruments, boxes, crates, agricultural implements, tool handles, turnery and veneer. It is a good firewood.

The bark is used as fish poison. In traditional medicine in Gabon and Congo, young children are bathed in a warm decoction of the bark to treat fever. In Congo a bark macerate is used as a bath to treat skin diseases and filariasis of the eye. A decoction of the bark mixed with sweet peppers is taken by nursing mothers to stimulate milk production. In Congo a bark extract is taken by men against gonorrhoea and by women against various menstrual problems. In Gabon bark decoctions are drunk against diarrhoea.

The wood of Bobgunnia fistuloides has been traded internationally as ‘pau rosa’, sometimes as a substitute of rosewood (Dalbergia spp.), but trade is insignificant since the species has become more rare. Gabon exported on average 1600 m³ of logs per year from 1994 to 1999 and 3150 m³/year in 2000–2003.

The heartwood is pale red, turning purplish upon exposure, with yellowish or reddish brown stripes on quarter-sawn surfaces, and clearly demarcated from the 1–2 cm thick, whitish or yellowish sapwood. The grain is wavy or slightly interlocked, texture fine to coarse and even.

The wood is very heavy, with a density of about 1020 kg/m³ at 12% moisture content, and very hard. It dries slowly but fairly well, with little risk of distortion but a high risk of surface checking and some end checking. The shrinkage rates are moderate, from green to oven dry 3.8–4.8% radial and 5.7–6.2% tangential. Once dry the wood is moderately stable to unstable in service. At 12% moisture content, the modulus of rupture is (149–)166–223 N/mm², modulus of elasticity 16,475–17,840(–21,290) N/mm², compression parallel to grain 90–95 N/mm², shear 11–12 N/mm², cleavage 20–40 N/mm and Chalais-Meudon side hardness 8.7–9.5.

Considerable force is required for sawing; saw blades may vibrate or overheat. The wood works well with machine tools. For such a hard and dense wood, the blunting effect on cutting edges is only average and special alloy tools are not required. The wood planes and finishes fairly well, but sometimes surfaces are slightly woolly. The nailing and screwing properties are good, but pre-boring is required. The wood has a tendency to char upon boring. It glues satisfactorily. The slicing properties are good but the wood is not suitable for rotary peeling. It is durable, being resistant to fungal, dry-wood borer and termite attacks, but damage by pinhole borers in the sapwood has been reported. The wood is suitable for use in contact with the ground or fresh water. The heartwood is resistant to impregnation with preservatives. Sawdust may be irritating to mucous membranes in wood workers.

The wood is resistant to some acid products. It contains 32–35% cellulose, 26–28% lignin, 12.5–16.5% pentosan, 0.1–0.4% ash and little silica. The solubility is 16.0–25.5% in alcohol-benzene, 1.8–2.3% in hot water and 13.2–18.1% in a 1% NaOH solution.

• Medium-sized tree up to 25(–40) m tall; bole often slightly sinuous or twisted, up to 80(–120) cm in diameter, base slightly swollen and fluted; bark surface slightly fissured, scaly leaving large irregular patches, greenish yellow to whitish grey, inner bark fibrous, creamy to yellowish with yellowish brown streaks, with watery exudate; crown often large, with sinuous branches; twigs glabrous.
• Leaves alternate, imparipinnately compound with (5–)8–20 leaflets; stipules minute, persistent; petiole 2–6.5 cm long, rachis 14–27 cm long, nearly glabrous; petiolules c. 0.5 cm long, wrinkled, slightly hairy; leaflets alternate, elliptical to ovate, 5–12.5 cm × 3–6.5 cm, usually increasing in size towards leaf apex, base obtuse, apex acuminate, nearly glabrous, pinnately veined.
• Inflorescence an axillary false raceme up to 30 cm long, many-flowered, glabrous to slightly hairy, with flowers in groups of 1–4.
• Flowers bisexual, zygomorphic, sweet scented; pedicel 1–2 cm long; calyx irregularly 2–4(–7)-lobed; petal 1, nearly round to broadly obovate, 2–3 cm × 1.5–2 cm, pinkish white with yellow patch at base inside, crinkled, short-hairy outside, with short claw at base; stamens numerous, unequal, up to 2.5 cm long, bright orange; ovary superior, c. 1 cm long, glabrous, on up to 1 cm long stipe, style short.
• Fruit a woody, cylindrical pod up to 30(–80) cm × 1.5–3 cm, straight or curved, shiny reddish brown to dark brown or black when ripe, indehiscent, many-seeded.
• Seeds oblong to kidney-shaped, flattened, c. 1 cm × 1 cm, shiny brown or greyish.
• Seedling with epigeal germination; hypocotyl 3–4(–7) cm long, epicotyl c. 2 cm long, hairy; cotyledons leafy, rounded, c. 3 cm long; first leaves alternate, simple.

Bobgunnia comprises 2 species and is confined to mainland tropical Africa. It has been separated from Swartzia, a genus of over 100 species in tropical America, mainly on the basis of seed characteristics, but flower structure is similar and molecular studies also point to inclusion in Swartzia.

Traditionally, Bobgunnia and Swartzia are placed in Caesalpiniaceae (Leguminosae - Caesalpinioideae), but chemistry, cytology, palynology and wood anatomy support the inclusion in Papilionaceae (Leguminosae - Papilionoideae), and this is also supported by molecular studies.

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; 25: intervessel pits small (4–7 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; 47: 5–20 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: 80: axial parenchyma aliform; (81: axial parenchyma lozenge-aliform); 82: axial parenchyma winged-aliform; 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; 104: all ray cells procumbent; 115: 4–12 rays per mm; 116: ≥ 12 rays per mm.
• Storied structure: 118: all rays storied; 120: axial parenchyma and/or vessel elements storied.
• Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells; (143: prismatic crystals in fibres).

Flowering is reported in May in Côte d’Ivoire and in July in Ghana, but in Gabon flowering and fruiting are asynchronous throughout the year. Fruits have a strong yeasty smell and are eaten by elephants, which serve as the main seed dispersers. Seedlings are commonly found in elephant dung.

Bobgunnia fistuloides is usually a tree of the second storey of rainforest and semi-deciduous forest, up to 500 m altitude.

Good natural regeneration has been observed in logged-over forest in Gabon. There are 3000–5000 seeds per kg. The seeds start germinating 5–10(–20) days after sowing, and the germination rate is high. In Congo seeds are extracted from the fruits and dried in the sun for 2–4 days; germination started after 7–8 days and the germination rate was up to 96%.

Larger trees of Bobgunnia fistuloides occur scattered in the forest and are generally uncommon. In forest in Cameroon an average density of 0.01 tree with a bole diameter of more than 60 cm has been recorded per ha, with an average wood volume of 0.1 m³/ha. In Gabon a mean wood volume of 0.4 m³/ha has been reported.

The minimum bole diameter for harvesting is 50 cm in Cameroon, 60 cm in Gabon and 70 cm in the Central African Republic.

Logs do not float in water and cannot be transported by river.

Bobgunnia fistuloides is classified as endangered in the IUCN Red list. Although widespread in West and Central Africa, it only occurs in closed forest and is exploited at a moderately high level for its decorative timber, and its population is estimated to have been reduced by 80% during the last 3 generations. Its natural regeneration may be hampered locally by the absence of its main seed disperser, the forest elephant.

Bobgunnia fistuloides yields an excellent decorative timber, but due to exploitation, loss of habitat and poor regeneration it is classified as endangered. Regulation of the trade of its wood under CITES regulations is recommended. It deserves more research attention, especially on propagation methods and silvicultural management to judge its prospects for sustainable production of its valuable timber. Of its traditional uses, the medicinal ones may remain most important.

• African Regional Workshop (Conservation & Sustainable Management of Trees, Zimbabwe), 1998. Bobgunnia fistuloides. In: IUCN. 2011 IUCN Red list of threatened species. Version 2011.2. [Internet] http://www.iucnredlist.org. February 2012.

• Aubréville, A., 1968. Légumineuses - Caesalpinioidées (Leguminosae - Caesalpinioideae). Flore du Gabon. Volume 15. Muséum National d’Histoire Naturelle, Paris, France. 362 pp.

• Bolza, E. & Keating, W.G., 1972. African timbers: the properties, uses and characteristics of 700 species. Division of Building Research, CSIRO, Melbourne, Australia. 710 pp.

• Burkill, H.M., 1995. The useful plants of West Tropical Africa. 2nd Edition. Volume 3, Families J–L. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 857 pp.

• CIRAD Forestry Department, 2009. Pao rosa. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/ faro.pdf. February 2012.

• de la Mensbruge, G., 1966. La germination et les plantules des essences arborées de la forêt dense humide de la Côte d’Ivoire. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 389 pp.

• de Saint-Aubin, G., 1963. La forêt du Gabon. Publication No 21 du Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 208 pp.

• Kirkbride, J.H. & Wiersema, J.H., 1997. Bobgunnia, a new African genus of the tribe Swartzieae (Fabaceae, Faboideae). Brittonia 49(1): 1–23.

• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.

• Vivien, J. & Faure, J.J., 1985. Arbres des forêts denses d’Afrique Centrale. Agence de Coopération Culturelle et Technique, Paris, France. 565 pp.

• Aubréville, A., 1959. La flore forestière de la Côte d’Ivoire. Deuxième édition révisée. Tome premier. Publication No 15. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 369 pp.

• Aubréville, A., 1970. Légumineuses - Césalpinioidées (Leguminosae - Caesalpinioideae). Flore du Cameroun. Volume 9. Muséum National d’Histoire Naturelle, Paris, France. 339 pp.

• Hawthorne, W.D., 1995. Ecological profiles of Ghanaian forest trees. Tropical Forestry Papers 29. Oxford Forestry Institute, Department of Plant Sciences, University of Oxford, United Kingdom. 345 pp.

• Hawthorne, W. & Jongkind, C., 2006. Woody plants of western African forests: a guide to the forest trees, shrubs and lianes from Senegal to Ghana. Kew Publishing, Royal Botanic Gardens, Kew, United Kingdom. 1023 pp.

• Hepper, F.N., 1958. Papilionaceae. In: Keay, R.W.J. (Editor). Flora of West Tropical Africa. Volume 1, part 2. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 505–587.

• Irvine, F.R., 1961. Woody plants of Ghana, with special reference to their uses. Oxford University Press, London, United Kingdom. 868 pp.

• Keay, R.W.J., 1989. Trees of Nigeria. A revised version of Nigerian trees (1960, 1964) by Keay, R.W.J., Onochie, C.F.A. & Stanfield, D.P. Clarendon Press, Oxford, United Kingdom. 476 pp.

• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.

• Normand, D. & Paquis, J., 1976. Manuel d’identification des bois commerciaux. Tome 2. Afrique guinéo-congolaise. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 335 pp.

• Sallenave, P., 1955. Propriétés physiques et mécaniques des bois tropicaux de l’Union française. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 129 pp.

• Savard, J., Besson, A. & Morize, S., 1954. Analyse chimique des bois tropicaux. Publication No 5, Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 191 pp.

• Tailfer, Y., 1989. La forêt dense d’Afrique centrale. Identification pratique des principaux arbres. Tome 2. CTA, Wageningen, Pays-Bas. pp. 465–1271.

• White, L. & Abernethy, K., 1997. A guide to the vegetation of the Lopé Reserve, Gabon. 2nd edition. Wildlife Conservation Society, New York, United States. 224 pp.

• Wilczek, R., Léonard, J., Hauman, L., Hoyle, A.C., Steyaert, R., Gilbert, G. & Boutique, R., 1952. Caesalpiniaceae. In: Robyns, W., Staner, P., Demaret, F., Germain, R., Gilbert, G., Hauman, L., Homès, M., Jurion, F., Lebrun, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 3. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 234–554.

• Wilks, C. & Issembé, Y., 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata, Guinée Equatoriale. 546 pp.

• Aubréville, A., 1970. Légumineuses - Césalpinioidées (Leguminosae - Caesalpinioideae). Flore du Cameroun. Volume 9. Muséum National d’Histoire Naturelle, Paris, France. 339 pp.

• Wilks, C. & Issembé, Y., 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata, Guinée Equatoriale. 546 pp.

• L.P.A. Oyen, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Oyen, L.P.A., 2012. Bobgunnia fistuloides (Harms) J.H.Kirkbr. & Wiersema. [Internet] Record from PROTA4U. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 2 June 2025.

• See the Prota4U database.