Celtis mildbraedii

Family

Celtidaceae (APG: Cannabaceae)

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Synonyms

Celtis soyauxii Engl.

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Vernacular names

Red-fruited white stinkwood, Natal white stinkwood, red-fruited celtis (En). Celtis d’Afrique (Fr). Mokolongo, mokalungo (Sw).

Origin and geographic distribution

Celtis mildbraedii occurs from Guinea eastward to Sudan and southern Kenya and northern Tanzania, and southward to DR Congo and northern Angola. It also occurs in a disjunct area in southern Africa, from eastern Zimbabwe and southern Mozambique to northern South Africa and Swaziland. Finally it is found in the most northern part of Madagascar.

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Uses

The wood of Celtis mildbraedii, traded as ‘ohia’ or ‘African celtis’, is used for a variety of purposes. Traditionally, it is used for poles in house building and for pestles, tool handles and spoons. The wood is suitable for heavy construction, flooring, joinery, interior trim, mine props, railway sleepers, ship building, vehicle bodies, furniture, ladders, sporting goods, boxes, crates, agricultural implements, veneer, plywood, hardboard and particle board. It is an excellent firewood, burning slowly.
In Côte d’Ivoire and Uganda, trees are left for shade in plantations of banana, cocoa, coffee and tea. Celtis mildbraedii is planted as an ornamental tree in large gardens, parks and along streets, mainly in South Africa. The bark has analgesic properties. In Cameroon bark decoctions are used as a wash to invigorate seriously weakened babies. They are also taken together with Solanum anguivi Lam. fruits to treat venereal diseases. In Congo bark decoctions enter into a medicine taken orally or as enema against menstrual problems. In Angola a decoction of the root bark is drunk to treat malaria. In Cameroon root ash mixed with palm oil is applied to scarifications as a treatment of headache. In Angola a tea of the root is given to children against constipation, but also against diarrhoea, cough, urinary complains and heart problems. A tea of the root or leaves is drunk against intercostal pain. A maceration of leafy twigs is applied as a bath or lotion to treat headache and as vermifuge. In Angola a hot water extract of the flowers with ash is rubbed onto the belly to promote childbirth. Flowers also enter into a rub against hernia. In Angola pounded leaves are made into a fish poison.

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Production and international trade

The wood of Celtis mildbraedii, traded together with that of several other Celtis species, occasionally enters the international market, but data on amounts traded are limited. It is more important in local markets. In 2005 Ghana exported 4000 m³ of Celtis veneer at an average price of US$ 310, and in 2006 3000 m³ at US$ 363, and in 2009 3100 m³ of rotary veneer, 80 m³ of sliced veneer and 120 m³ of plywood. The wood is regarded as valuable in local markets.

Properties

The heartwood is white to pale yellow or greenish, darkening upon exposure to greyish white, and indistinctly demarcated from the sapwood. The grain is often interlocked, sometimes straight, texture rather fine and even. Surfaces are often lustrous. Freshly cut wood has an unpleasant smell.
The wood is medium-weight, with a density of 600–785 kg/m³ at 12% moisture content, and hard. On drying there is some risk of end splitting and distortion. Some reports indicate that defects may be serious and recommend application of an end-coating product and weighing down drying piles. The rates of shrinkage are moderate, from green to oven dry 4.1–5.2% radial and 7.7–9.1% tangential. The wood is often discoloured by blue or black stains if it is not dried rapidly after felling. Once dry, the wood is moderately stable in service.
At 12% moisture content, modulus of rupture is (49–)75–182 N/mm², modulus of elasticity 8200–16,500 N/mm², compression parallel to grain 46–82 N/mm², shear 17–26 N/mm², cleavage 14–25 N/mm and Chalais-Meudon side hardness 3.4–6.5.
The wood of Celtis mildbraedii works fairly well with machine tools and slightly more difficult with hand tools. It has a moderate to fairly high blunting effect on saw teeth and cutting edges, and stellite-tipped saws and tungsten-carbide tool edges are recommended. Rip-sawing and band-sawing require considerable force. Straight-grained wood planes well, but a reduced cutting angle of 15° is recommended to avoid tearing in wood with interlocked grain. The wood is difficult to nail and screw; pre-boring is recommended. It glues well. The veneering properties are variable as is the quality of veneer. The wood has a low durability. It is susceptible to attacks by blue-stain fungi and insects, including termites and Lyctus borers. The heartwood is moderately resistant to treatment with preservatives, the sapwood is permeable. Wood dust may cause allergic reactions and skin irritation in wood workers.
In a test in Congo, chemically pulped wood yielded about 50% pulp. Wood thicker than 1.5 cm is moderately easily inflammable, thinner wood is easily inflammable. On burning, the wood of samples tested in Nigeria gave less than 1% ash.

Adulterations and substitutes

The wood of Celtis mildbraedii is similar in appearance and properties to that of Celtis zenkeri Engl. and Celtis gomphophylla Baker; they are all traded as ‘ohia’ or ‘African celtis’. It is also similar to that of Celtis adolfi-friderici Engl., which may also be traded as ‘African celtis’.

Description

Evergreen or deciduous, medium-sized to large tree up to 50 m tall; bole branchless for up 30 m, slender, straight, up to 100 cm in diameter, with sharp buttresses up to 5 m high and 2 m wide; bark surface smooth or scaling in small disks, silvery to pale brown, inner bark fibrous, dark brown with yellow to off-white layers; crown small and dense; branches often drooping, with conspicuous pale lenticels; twigs rusty hairy. Leaves alternate, simple; stipules lanceolate, 4–5 mm long, tawny-hairy; petiole 3–10 mm long; blade elliptical to elliptical-obovate, (7.5–)9–15 cm × 4–5(–8) cm, base slightly obliquely cuneate, apex acuminate, margins obscurely to coarsely toothed in the upper half, papery to thin-leathery, glabrous, 3-veined from the base and additionally with (2–)3–6 pairs of lateral veins. Inflorescence an axillary cyme 0.5–1.5 cm long, short-hairy, many-flowered. Flowers unisexual or bisexual, regular, usually 5-merous, small, greenish; pedicel 0.5–2 mm long; tepals 1.5–2.5 mm long, hairy; stamens free, incurved in bud and later spreading; ovary superior, ovoid, often with a ring of sparse hairs at the base, otherwise nearly glabrous, 1-celled, styles 2, 2-lobed; male flowers numerous and densely clustered, with rudimentary ovary; female flowers and/or bisexual flowers at tops of upper inflorescences, female flowers with rudimentary stamens. Fruit an ovoid-ellipsoid drupe 0.5–1 cm long, reddish when ripe, glabrous, crowned at top by remains of styles; stone rhomboid-polygonal, c. 6 mm long, rough, 1-seeded. Seedling with epigeal germination; hypocotyl 4–5 cm long, epicotyl c. 1 cm long, hairy; cotyledons leafy, 1.5–2 cm long, 2-lobed at apex; first leaves alternate.

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Other botanical information

Celtis comprises about 100 species and is widespread in all tropical, subtropical and temperate regions. For tropical Africa 11 species have been recorded, 2 of which are endemic to Madagascar. Celtis is taxonomically a difficult genus, showing much morphological variability. Traditionally, it has been treated as part of the family Ulmaceae, but later it was often considered to belong to a separate family, Celtidaceae, whereas from most recent research it was proposed to take up the latter family in Cannabaceae.
Celtis mildbraedii resembles Celtis zenkeri Engl. and these species have been confused in the literature; they have both been called Celtis soyauxii Engl., which is now considered a synonym of Celtis zenkeri. The latter species usually has entire leaves with straight and parallel tertiary veins (reticulate in Celtis mildbraedii), and ovoid fruit stones. Moreover, Celtis mildbraedii often has a straighter and more slender and cylindrical bole than Celtis zenkeri.
Celtis prantlii Priemer ex Engl. (synonyms: Celtis brownii Rendle, Celtis philippensis auct. non Blanco, Celtis wightii auct. non Planch.) resembles Celtis mildbraedii and has a similar area of distribution, although it does not occur in southern Africa and Madagascar. It is a small, deciduous tree up to 15 m tall. Its yellowish white, quite heavy and hard wood is used for construction, carpentry, pestles and canoes, and also as firewood. In Kenya root decoctions are taken to treat diarrhoea and in Côte d’Ivoire leaf preparations are applied to eczema.

Anatomy

Wood-anatomical description (IAWA hardwood codes):
Growth rings: 1: growth ring boundaries distinct. 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); 26: intervessel pits medium (7–10 μm); 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 31: vessel-ray pits with much reduced borders to apparently simple: pits rounded or angular; 42: mean tangential diameter of vessel lumina 100–200 μm; 47: 5–20 vessels per square millimetre; 56: tyloses common. Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 69: fibres thin- to 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); (86: axial parenchyma in narrow bands or lines up to three cells wide); (89: axial parenchyma in marginal or in seemingly marginal bands); 92: four (3–4) cells per parenchyma strand; 93: eight (5–8) cells per parenchyma strand. Rays: 97: ray width 1–3 cells; 98: larger rays commonly 4- to 10-seriate; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 107: body ray cells procumbent with mostly 2–4 rows of upright and/or square marginal cells; (108: body ray cells procumbent with over 4 rows of upright and/or square marginal cells); 113: disjunctive ray parenchyma cell walls present; 115: 4–12 rays per mm. Mineral inclusions: 136: prismatic crystals present; 137: prismatic crystals in upright and/or square ray cells; (138: prismatic crystals in procumbent ray cells); 141: prismatic crystals in non-chambered axial parenchyma cells; 142: prismatic crystals in chambered axial parenchyma cells; 154: more than one crystal of about the same size per cell or chamber; (155: two distinct sizes of crystals per cell or chamber); (157: crystals in tyloses).
(E.E. Mwakalukwa, P.E. Gasson & E.A. Wheeler)

Growth and development

Celtis mildbraedii is classified as a shade-bearer. Germination is depressed in larger gaps in the forest, but established saplings grow well in forest gaps. Growth response of seedlings did not show a clear correlation with rainfall or soil fertility. Young trees may grow 1–2 m in length per year. In Ghana seedlings reached 1–3 m tall when 4 years old.
In Ghana Celtis mildbraedii flowers in January–April and August–September, and fruits ripen in February–April and August–September. In Benin it flowers in August and fruit can be found in August–October. In Zimbabwe and South Africa trees flower in September–October and fruits ripen in October–November. Trees with a bole diameter of 10 cm may already produce fruits. These are eaten by birds, including hornbills, and primates, which disperse the seeds. Seedlings may be abundant near mother trees.

Ecology

Celtis mildbraedii is common in lowland to submontane, evergreen and semi-deciduous forest, except in wetter localities, up to 1600 m altitude. In southern Africa and Madagascar, it is less common and occurs in somewhat drier conditions.

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Propagation and planting

Fruit stones are usually collected from the ground; they are usually produced in large quantities in the fruiting season. There are about 2500 stones per kg. Germination takes 2–4 weeks, and the germination rate is generally low. Wildlings are sometimes also collected for planting.

Management

In natural forest in Côte d’Ivoire, Celtis mildbraedii showed a positive response to thinning, about doubling the volume growth during the first 3 years after thinning. The trees can be pollarded.

Diseases and pests

Leaves often have dark brown galls 3–5 mm in diameter on both surfaces.

Harvesting

Logs should be extracted from the forest soon after felling or treated with preservatives to avoid attacks by blue-stain fungi and pinhole borers.

Handling after harvest

Logs should be converted soon after felling to avoid losses by blue-stain fungal attack.

Genetic resources and breeding

Celtis mildbraedii is very widespread. There are no indications that it is at risk of genetic erosion in tropical Africa. In South Africa it has been classified as vulnerable, but additional stands have been discovered later. The conservation status in Madagascar is not known.

Breeding

No selection programmes are known to exist.

Prospects

The wood of Celtis mildbraedii is likely to remain important for a variety of local uses. It may maintain its small role in international trade and even become more important, as it is a suitable substitute for several European timbers.

Major references

• 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., 2000. The useful plants of West Tropical Africa. 2nd Edition. Volume 5, Families S–Z, Addenda. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 686 pp.
• CIRAD Forestry Department, 2009. Celtis. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/celtis.pdf. Accessed November 2009.
• Coates Palgrave, K., 2002. Trees of southern Africa. 3rd Edition. Struik Publishers, Cape Town, South Africa. 1212 pp.
• Hauman, L., 1948. Ulmaceae. In: Robyns, W., Staner, P., De Wildeman, E., Germain, R., Gilbert, G., Hauman, L., Homès, M., Lebrun, J., Louis, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 1. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 39–51.
• 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.
• Polhill, R.M., 1966. Ulmaceae. In: Hubbard, O.B.E. & Milne-Redhead, E. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 15 pp.
• Sattarian, A., 2006. Contribution to the biosystematics of Celtis L. (Celtidaceae) with special emphasis on the African species. PhD thesis. Wageningen University, Wageningen, Netherlands. 142 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.
• Wilmot-Dear, C.M., 1991. Ulmaceae. In: Launert, E. & Pope, G.V. (Editors). Flora Zambesiaca. Volume 9, part 6. Flora Zambesiaca Managing Committee, London, United Kingdom. pp. 1–10.

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Other references

• Ahonkhai, S.I., 1988. Chemical characterization of the ashes of some African hardwoods. Wood Science and Technology 22(3): 227–229.
• Anonymous, 1965. Neue Importholzkunde. Teil I Afrika. Ohia. Holzzentralblatt 91: 67–68.
• 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.
• Baerts, M. & Lehmann, J., 2012. Sarcostemma viminale. [Internet] Prelude Medicinal Plants Database. Metafro-Infosys, Royal Museum for Central Africa, Tervuren, Belgium http://www.metafro.be/prelude. Accessed January 2012.
• Bouquet, A., 1969. Féticheurs et médecines traditionnelles du Congo (Brazzaville). Mémoires ORSTOM No 36. Office de la Recherche Scientifique et Technique Outre-Mer. Paris, France. 282 pp.
• 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.
• Farmer, R.H., 1972. Handbook of hardwoods. 2nd Edition. Her Majesty’s Stationery Office, London, United Kingdom. 243 pp.
• Herzog, F., 1994. Multipurpose shade trees in coffee and cocoa plantations in Côte d’Ivoire. Agroforestry Systems 27: 259–267.
• Irvine, F.R., 1969. West African agriculture, 3rd Edition. Volume 2: West African Crops. Oxford University Press, London, United Kingdom. 272 pp.
• Istas, J.R., 1956. Improvement of the paper-mill quality of gray pulps made of leafy species of the Congo. Influence of the parenchyma. Bulletin Agricole du Congo 47: 1537–1549.
• Katende, A.B., Birnie, A. & Tengnäs, B., 1995. Useful trees and shrubs for Uganda: identification, propagation and management for agricultural and pastoral communities. Technical Handbook 10. Regional Soil Conservation Unit, Nairobi, Kenya. 710 pp.
• Letouzey, R., 1968. Ulmaceae. Flore du Cameroun. Volume 8. Muséum National d’Histoire Naturelle, Paris, France. pp. 3–65.
• Lovett, J.C., Ruffo, C.K., Gereau, R.E. & Taplin, J.R.D., 2007. Field guide to the moist forest trees of Tanzania. [Internet] Centre for Ecology Law and Policy, Environment Department, University of York, York, United Kingdom. http://celp.org.uk/ projects/ tzforeco/. Accessed January 2012.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Ocloo, J.K. & Laing, E., 2003. Correlation of relative density and strength properties with anatomical properties of the wood of Ghanaian Celtis species. Discovery and Innovation 15(3–4): 186–196.
• Ofori, J., Brentuo, B., Mensah, M., Mohammed, A.I. & Boamah-Tawiah, R., 2009. Properties of 10 Ghanaian high density lesser-used-species of importance to bridge construction. Part 1: green moisture content, basic density and shrinkage characteristics. Ghana Journal of Forestry 25: 67–77.
• Ofori, J., Mohammed, A.I., Brentuo, B., Mensah, M. & Boamah-Tawiah, R., 2009. Properties of 10 Ghanaian high density lesser-used-species of importance to bridge construction. Part 2: mechanical strength properties. Ghana Journal of Forestry 25: 78–92.
• Veenendaal, E.M., Swaine, M.D., Lecha, R.T., Walsh, M.F., Abebrese, I.K. & Owusu-Afriyie, K., 1996. Responses of West African forest tree seedlings to irradiance and soil fertility. Functional Ecology 10(4): 501–511.
• Whitney, K.D., Fogiel, M.K., Lamperti, A.M., Holbrook, K.M., Stauffer, D.J., Hardesty, B.D., Parker, V.T. & Smith, T.B., 1998. Seed dispersal by Ceratogymna hornbills in the Dja Reserve, Cameroon. Journal of Tropical Ecology 14(3): 351–371.
• Wilmot-Dear, C.M., 1999. FSA contributions 13: Ulmaceae. Bothalia 29(2): 239–247.

Afriref references

Sources of illustration

• Akoègninou, A., van der Burg, W.J. & van der Maesen, L.J.G. (Editors), 2006. Flore analytique du Bénin. Backhuys Publishers, Leiden, Netherlands. 1034 pp.

Author(s)

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

Editors

•	R.H.M.J. Lemmens PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	D. Louppe CIRAD, Département Environnements et Sociétés, Cirad es-dir, Campus international de Baillarguet, TA C 105 / D (Bât. C, Bur. 113), 34398 Montpellier Cédex 5, France
•	A.A. Oteng-Amoako Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Associate editors

•	E.A. Obeng Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Photo editor

•	G.H. Schmelzer PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Oyen, L.P.A., 2012. Celtis mildbraedii Engl. [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 .

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