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Swietenia macrophylla King

Protologue
Hook.f., Icon. pl. 16: t. 1550 (1886).
Family
Meliaceae
Chromosome number
2n = 24, 46, 54, 108
Vernacular names
Big-leaved mahogany, large-leaved mahogany, broad-leaved mahogany, Honduras mahogany (En). Acajou du Honduras, acajou d’Amιrique, mahogany grandes feuilles (Fr). Mogno (Po).
Origin and geographic distribution
Swietenia macrophylla is native to the mainland of Central and South America, from Mexico to Peru, Bolivia and Brazil, which makes it the most widely distributed Swietenia species. The wood has been internationally traded for over 400 years. Big-leaved mahogany was introduced in India from Belize in 1872, and has since been planted throughout the tropics in timber plantations and as an ornamental, also on a small scale in tropical Africa. Attempts to introduce mahogany to tropical Africa (e.g. in Sierra Leone, Nigeria, Uganda) were largely unsuccessful due to the severity of shoot borer attack on young plants. Trial plantations in Mauritius were initially unsuccessful, but later Swietenia macrophylla was used successfully for reforestation at low elevations. Extensive plantations exist in Indonesia, Fiji and Sri Lanka.
Uses
Swietenia wood (mahogany) is regarded as the world’s finest timber for high-class furniture and cabinet work. Its popularity is especially due to its attractive appearance in combination with ease of working, excellent finishing qualities and dimensional stability. It is also often used for interior trim such as panelling, doors and decorative borders. It is used for boat building, often as a decorative wood for luxury yachts and ocean liners, but sometimes also as plywood for planking and deck housing. Its outstanding technical qualities make it particularly suitable for precision woodwork such as models and patterns, instrument cases, clocks, printer’s blocks and parts of musical instruments; for these purposes, uniform straight-grained material is used. Other minor uses include burial caskets, wood carvings, novelties, toys and turnery.
An oil, which is very bitter and purgative, can be extracted from the seeds, but commercial exploitation of the oil seems unlikely. The bark is bitter and astringent, and has been used as a febrifuge and also for dyeing and tanning leather. A gum is produced for Bombay (India) markets from cuts in the bark, where it is sold both pure and mixed with other gums. Various medicinal uses of various parts of the tree are reported from tropical America. The crushed fruit shells have been used as a potting medium. Swietenia macrophylla is also used in reforestation programmes and agroforestry systems, and as a shade tree in young plantations of other timber species, and is occasionally planted as ornamental.
Production and international trade
Mahogany is one of the most important tropical timbers on the world market. Most mahogany traded is from natural stands, and only small quantities are available from planted trees. The annual export from tropical America exceeds 120,000 m³. In 1996–2002 the average annual export of Swietenia macrophylla timber was 59,500 m³ from Brazil, 30,500 m³ from Peru, 15,000 m³ from Bolivia and 14,000 m³ from countries in Central America. In 2002 the price of sawn Swietenia macrophylla timber from Bolivia was about US$ 980/m³. The most important importer is the United States with an import of 76,000 m³/year, which is over 60% of global trade. It has been estimated that the area planted with Swietenia macrophylla in the tropics is 200,000 ha, but the area in Africa is insignificant.
Properties
The heartwood is reddish or pinkish, the colour darkening with age to a deep red or brown, distinctly demarcated from the usually yellowish sapwood, which is up to 40 mm wide. The grain is interlocked, sometimes straight, texture fine to moderately coarse. The surfaces are glossy, with golden lustre, and the wood is often nicely figured because of irregular grain.
Big-leaved mahogany wood is a medium-weight wood. The density is (450–) 530–670(–840) kg/m³ at 12% moisture content, with that of plantation-grown trees often somewhat less than that of trees from natural forest. The rates of shrinkage are low, from green to 12% moisture content 1.4% radial and 2.2% tangential, and from green to oven dry 2.1–3.3% radial and 2.9–5.7% tangential. The wood seasons well, without much checking or distortion. Planks of 50 mm thick can be air dried in 11 weeks from 40% moisture content to 15%, boards of 25 mm thick in 6 weeks. The wood kiln dries satisfactorily when moderate schedules are used (temperatures of 43–76°C and corresponding relative humidities of 75–33%). Planks of 50 mm thick can be kiln dried in approximately 8 days from 40% moisture content to 15%, and boards of 25 mm in 4 days. Planks of 41 mm thick can be kiln dried in 13 days from 70% moisture content to 15%. After drying, the wood is stable in service.
The wood is comparatively soft. At 12% moisture content the modulus of rupture is 72–98 N/mm², modulus of elasticity 9300–12,100 N/mm², compression parallel to grain 43–62 N/mm², shear 13.5 N/mm² and Janka side hardness 3560 N.
The wood saws, planes and moulds easily in both green and dry condition. In general it finishes to a smooth surface, but a woolly surface may occur on bands of reaction wood or interlocked grain. Finishing is easy and the wood takes an excellent polish. Gluing and nailing properties are good, but discoloration in contact with iron, copper and brass may occur under humid conditions. The wood slices and rotary cuts into fine and decorative veneer, without preliminary treatment, at a peeling angle of 92°. The veneer can be glued with casein extended with 30% lime, to produce plywood of satisfactory quality. Satisfactory results are obtained with pulping (kraft pulp yield of 49.5%).
The heartwood of trees from natural stands can be reasonably durable, but it is not considered suitable for applications in contact with the ground. Graveyard tests in Indonesia showed an average service life in contact with the ground of 2.7 years. The wood is resistant to wood-rotting fungi. The sapwood is susceptible to Lyctus borer attack and the heartwood may also be attacked by pinhole borers and termites; the wood has little resistance to marine borers. The wood is resistant to impregnation with preservatives by pressure methods, but plantation-grown wood can be amenable to boron diffusion techniques.
The wood contains 39–47% cellulose, 27–31% lignin, 16–18% pentosan, 0.5–0.6% ash and 0.1% silica. The solubility is 2.4% in alcohol-benzene, 0.4% in cold water, 4.5% in hot water and 19% in a 1% NaOH solution. The energy value of the wood is 19,600–20,300 kJ/kg. The wood contains essential oil which is rich in sesquiterpenes. The bark of Swietenia macrophylla showed significant in-vivo antimalarial activity in tests with rodents.
Adulterations and substitutes
True mahogany timber from Swietenia spp. is hardly produced in tropical Africa, but the timber of several indigenous and more or less related species is traded as African mahogany, mainly Entandrophragma and Khaya spp., which produce wood with similar characteristics.
Description
Medium-sized to large monoecious tree up to 40(–60) m tall; bole usually straight and cylindrical, branchless for up to 18(–25) m, up to 150(–200) cm in diameter, often with broad and plank-like buttresses up to 5 m high; outer bark of older trees scaly, shaggy, deeply longitudinally furrowed and brownish grey to reddish brown, inner bark red-brown or pinkish red; crown dome-shaped, consisting of a few large, ascending branches. Leaves alternate, paripinnate with (2–)3–6(–8) pairs of leaflets; stipules absent; leaflets opposite, ovate-elliptical, 8–18 cm Χ 3–5.5 cm, entire, glabrous, pinnately veined. Inflorescence an axillary panicle 10–20 cm long, consisting of small cymes. Flowers unisexual, but with well-developed vestiges of the opposite sex, regular, 5-merous, small; pedicel slender, 1.5–2.5 mm long; calyx with broadly rounded lobes 1–1.5 mm long, hairy at margins; petals free, slightly contorted in bud, ovate-oblong, 5–6 mm long, hairy at margins; stamens united into a tube, with 10 sessile anthers at the mouth of the tube; disk annular; ovary superior, usually 5-celled, style short, with disk-shaped stigma. Fruit a woody, elongate-ovoid capsule 10–15(–22) cm long, greyish brown, opening by 5 valves, many-seeded. Seeds with large wing, flat, 7.5–10 cm long, dark brown, hanging down and overlapping in fruit; cotyledons thin. Seedling with hypogeal germination; first 3 leaves simple, later ones 3-foliolate or imparipinnate.
Other botanical information
Swietenia comprises 3 species and is most closely related to Khaya, which differs in its more globose fruits and seeds narrowly winged all round the margin. The 3 Swietenia species are difficult to distinguish from each other. Swietenia macrophylla differs from Swietenia mahagoni (L.) Jacq. in its larger leaflets, fruits and seeds, and from Swietenia humilis Zucc. in its stalked and shortly acuminate leaflets (sessile and long-acuminate in Swietenia humilis) and dark brown seeds (pale brown in Swietenia humilis). The natural distribution areas of the three species show only very slight overlap, but in areas where 2 species occur hybrids may be found.
Swietenia humilis has also been introduced in a few places in tropical Africa (e.g. in Malawi). It is a small to medium-sized tree up to 20 m tall, originating from Central America. Its timber is of little economic importance.
Anatomy
Wood-anatomical description (IAWA hardwood codes):
Growth rings: (1: growth ring boundaries distinct); (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); 24: intervessel pits minute ( 4 μm); 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; (46: 5 vessels per square millimetre); 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; 65: septate fibres present; 66: non-septate fibres present; 69: fibres thin- to thick-walled. Axial parenchyma: 78: axial parenchyma scanty paratracheal; 79: axial parenchyma vasicentric; 89: axial parenchyma in marginal or in seemingly marginal bands; 93: eight (5–8) cells per parenchyma strand; 94: over eight 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; 115: 4–12 rays per mm. Storied structure: (118: all rays storied); (122: rays and/or axial elements irregularly storied). Secretory elements and cambial variants: 131: intercellular canals of traumatic origin. Mineral inclusions: (136: prismatic crystals present); (137: prismatic crystals in upright and/or square ray cells); (141: prismatic crystals in non-chambered axial parenchyma cells); (142: prismatic crystals in chambered axial parenchyma cells).
(E. Uetimane, H. Beeckman & P.E. Gasson)
Growth and development
Healthy seeds start germinating about 10 days after sowing. Young trees have straight and slender stems, and branches are formed 2–3 m above the ground with a position oblique to the main stem. However, an unbranched stem up to 10 m tall may be formed before branching. Initial growth is fast, depending on site conditions. Under optimal conditions, seedlings may reach 3 m in one year and 6 m in two years. The average height of 2-year-old seedlings in experimental plantations in Nigeria at the beginning of the 1960s was 2 m, but there is no information on growth after 2 years. The seedlings and saplings are intolerant of deep shade although they will survive. Trees planted in the open field under optimal conditions may occasionally reach 50 cm in diameter in 25 years. In forest in the natural distribution area, trees take on average 105 years to reach a bole diameter of 80 cm, but the average diameter growth in natural forest has also been estimated at 0.4 cm/year. In well-managed stands it may be up to 1.4 cm/year. The maximum increment in height occurs at an age of 5–15 years, in diameter at 5–10 years and in timber volume at 20–25 years. Buttresses begin to develop soon, often already when the bole diameter is only 10 cm. Trees of 200 years old with a log diameter up to 190 cm and timber volume up to 29.5 m³ have been recorded.
Under favourable conditions, young trees may start to flower and produce seed when 12 years old, rarely already when 8 years old, but under natural conditions profuse production of seed is much later. Flowering trees have about 10 times as many male as female flowers, but the flowers of both sexes are very similar. Trees are sometimes functionally dioecious. In mixed inflorescences, male flowers open first, but self-pollination may occur. The flowers are probably pollinated by bees and moths, and outcrossing is the rule. Fruits may be produced once a year, and mast production of seeds occurs irregularly. Mature fruits can be found 10–11 months after flowering. The seeds are provided with a thin tail-like wing that makes them rotate when they fall, and are thus dispersed by wind occasionally as far as 500 m from the mother tree.
Ecology
Under natural conditions big-leaved mahogany thrives in both deciduous and evergreen rain forest and occurs scattered or in small groups, but more than 4–8 mature trees per ha are rarely encountered. It has been claimed that under natural conditions it regenerates in essentially even-aged stands after catastrophic disturbances of the forest, e.g. hurricanes, fire and flooding. Adult mahogany trees may survive such events because of their strong buttresses and resistance to fire, and spread their seeds into the resulting gaps or clearings. However, it has also been demonstrated that big-leaved mahogany does not require gaps for seed germination, probably except in evergreen forest where little light penetrates through the canopy.
The optimum annual rainfall is 1400–2500(–3500) mm with a dry period of 0–4 months. Swietenia macrophylla grows from sea-level to 1500 m altitude, in areas with a mean annual temperature of 20–28°C, the range of the coldest and warmest month being 11–22°C and 22–30°C, respectively. It is largely unspecific as to soil requirements. Within its natural range it has been found on alluvial soils, volcanic soils, heavy clays, lateritic soils, soils derived from limestone, granite and other sedimentary, igneous or metamorphic rock formations and even on shallow rendzinas. In plantations it performs best on deep, fertile, well-drained soils with a pH of 6.5–7.5. It does not tolerate waterlogging. In tropical America mahogany is among the pioneer species reoccupying degraded agricultural land. It has been shown that teak is outcompeted by mahogany in a mixed stand.
Propagation and planting
Fruits must be collected when ripe to achieve a good germination rate. The fruits open after 2 days of storage and the seeds are very viable with a germination rate of 60–95%. The seeds can be stored up to 2 months, or longer (up to one year) if kept cool (2–5°C) in sealed containers at about 45% relative humidity. The weight of 1000 seeds is 400–500 g.
Seeds are sown in the nursery in drills of 2–4 cm deep, or they are pushed into flat beds, leaving part of the wing exposed. Seed germination starts after about 10 days and continues for about 20 days. The seed bed should be well manured and shaded, but after 3–4 weeks the seedlings grow best in full sunlight. Seedlings may have a 70% survival rate, even if planted during the dry season, provided they are partially shaded and watered whenever soil moisture drops below 30%. For field planting, bare-root stock, balled seedlings, stumps (stem length 20 cm, root length 20–40 cm, diameter of root collar 0.5–2.5 cm) or striplings are used. Balled seedlings of 3–4 months old are preferred. Cuttings are relatively easy to establish from 3-year-old plants, but more difficult later. Swietenia macrophylla can be propagated by in-vitro culture and grafting; the latter method has been used to establish seed orchards. Spacing in the field is usually 2.5–3 m Χ 2.5–3 m. Profuse natural regeneration has been found in many mature mahogany plantations, and this may be used to establish the next crop, reducing nursery and plantation establishment costs.
Management
Although natural regeneration in Swietenia macrophylla stands may be plentiful, it is usual to plant seedlings raised in nurseries. One-year-old seedlings attain optimal height and diameter growth when fertilized with 3.6 g N, 2.4 g P2O5 and 3.6 g K2O. Phosphorus appears to be the most limiting element for seedling growth.
Monoculture plantations of mahogany are susceptible to pests, and for that reason mixed plantations with other fast-growing species are often preferred. Thinning usually starts 6 years after planting, and progressively reduces the number of trees to 220–400 trees/ha in plantations of 20 years old, and to 120–150 trees/ha in 35-year-old plantations. The rotation is usually 40–60 years.
Diseases and pests
Several fungal diseases affect seedlings in tropical Asia and islands of the Pacific, but these rarely cause serious damage. Shoot-boring moths of the genus Hypsipyla are the major limitation to plantation establishment, and this is also the case in tropical Africa, where Hypsipyla robusta is also a major pest in Entandrophragma and Khaya plantations. Attack by Hypsipyla can be successfully controlled with insecticides under nursery conditions. Ambrosia beetles may attack the wood, creating ‘ pin-holes’ visible in sawn timber. Termites may also cause damage in plantations.
Harvesting
Mahogany plantations are clear-cut when the rotation age (40–60 years) or a log diameter of 50 cm have been reached, and subsequently replanted with nursery-raised seedlings.
Yield
In rotations of 50–60 years, average annual volume increments of 15–20 m³/ha can be achieved for plantations, on poor sites 7–11 m³/ha.
Handling after harvest
Mahogany logs float in water and can be transported by river. The sapwood is susceptible to staining; an anti-sapstain dip should be used during drying.
Genetic resources
Populations of mahogany have been depleted through centuries of commercial exploitation in Central and South America. Although it is widespread, Swietenia macrophylla has become rare in parts of its natural area of distribution. It has been included in Appendix II of CITES since 2003, in addition to the other two Swietenia species, which were already included. This makes it subject to strict regulations concerning export and trade; exporting countries are required to verify that each shipment was legally acquired and that the harvest was non-detrimental to the survival of mahogany. In Brazil Swietenia macrophylla has been exploited only for the national market since 2003, and the minimum diameter limit for exploitation has been raised from 40 cm to 60 cm. There is no restriction for trade and export of plantation-grown timber. In tests in Central America using seedlings raised from seed of different origin, significant variation has been found both within and between Swietenia macrophylla populations, particularly in terms of height growth and susceptibility to pest attack. An analysis of the genetic diversity in and between populations in Brazil showed high variation. However, an analysis of the genetic diversity in Costa Rica indicated very little gene flow.
Breeding
Selection work has been carried out on an experimental scale (e.g. in Indonesia), especially towards improving growth and germination rates. Artificial hybridization between Swietenia spp. is possible, and hybrids often show promising features, combining for instance the fast growth of Swietenia macrophylla and the superior-quality wood of Swietenia mahagoni, and having greater resistance to diseases and pests.
Prospects
A major problem in mahogany plantations is the susceptibility to Hypsipyla attack. Research priority should be given to the selection of resistant trees which are fast-growing and have an acceptable wood quality. The establishment of optimal methods of vegetative propagation is urgently needed. In-vitro micropropagation techniques have already been developed, and these offer possibilities for the multiplication of pest-resistant genotypes. Developments in research and breeding of mahogany should be closely monitored because they may offer new opportunities for the establishment of mahogany plantations in tropical Africa, in addition to African mahogany (Entandrophragma and Khaya) and also in the light of the successful Swietenia plantations in tropical Asia and islands of the Pacific Ocean.
Major references
• Blundell, A.G., 2004. A review of the CITES listing of big-leaf mahogany. Oryx 38(1): 84–90.
• Brown, N., Jennings, S. & Clements, T., 2003. The ecology, silviculture and biogeography of mahogany (Swietenia macrophylla): a critical review of the evidence. Perspectives in Plant Ecology, Evolution and Systematics 6(1–2): 37–49.
• ITTO, 2004. Making the mahogany trade work. Report of the workshop on capacity building for the implementation of the CITES Appendix-II listing of mahogany. ITTO Technical Series No 22. International Tropical Timber Organization. 54 pp.
• Mayhew, J. & Newton, A.C., 1998. The silviculture of mahogany. CAB International, Wallingford, Oxon, United Kingdom. 226 pp.
• Prawirohatmadjo, S., Suranto, J., Keating, W.G., Ani Sulaiman, & Sosef, M.S.M., 1993. Swietenia Jacq. In: Soerianegara, I. & Lemmens, R.H.M.J. (Editors). Plant Resources of South-East Asia No 5(1). Timber trees: Major commercial timbers. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 442–447.
• World Agroforestry Centre, undated. Agroforestree Database. [Internet] World Agroforestry Centre (ICRAF), Nairobi, Kenya. http://www.worldagroforestry.org/ resources/databases/ agroforestree. Accessed April 2005.
Other references
• Burkill, H.M., 1997. The useful plants of West Tropical Africa. 2nd Edition. Volume 4, Families M–R. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 969 pp.
• Helgason, T., Russell, S.J., Monro, A.K. & Vogel, J.C., 1996. What is mahogany? The importance of a taxonomic framework for conservation. Botanical Journal of the Linnean Society 122: 47–59.
• InsideWood, undated. [Internet] http://insidewood.lib.ncsu.edu/search/. Accessed May 2007.
• Lamb, F.B., 1966. Mahogany of tropical America, its ecology and management. The University of Michigan Press, Michigan. 220 pp.
• Lowe, A.J., Jourde, B., Breyne, P., Colpaert, N., Navarro, C., Wilson, J. & Cavers, S., 2003. Fine scale genetic structure and gene flow within Costa Rican populations of mahogany (Swietenia macrophylla). Heredity 90(3): 268–275.
• Richter, H.G. & Dallwitz, M.J., 2000. Commercial timbers: descriptions, illustrations, identification, and information retrieval. [Internet]. Version 18th October 2002. http://delta-intkey.com/wood/index.htm. Accessed April 2005.
• Snook, L.K., 1996. Catastrophic disturbance, logging and the ecology of mahogany (Swietenia macrophylla King): grounds for listing a major tropical timber species in CITES. Botanical Journal of the Linnean Society 122: 35–46.
• Styles, B.T., 1981. Swietenioideae. In: Pennington, T.D. (Editor). Meliaceae. Flora Neotropica. Monograph No 28. New York Botanical Garden, New York, United States. pp. 359–418.
• Tillier, S., 1995. Le mahogany grandes feuilles en Martinique. Bois et Forκts des Tropiques 244: 55–65.
• Weaver, P.L. & Francis, J.K., 1988. Growth of teak, mahogany and Spanish cedar on St. Croix, U.S. Virgin Islands. Turrialba 38(4): 308–317.
• Yao, C.E., 1981. Survival and growth of mahogany (Swietenia macrophylla King) seedlings under fertilized grassland condition. Sylvatrop 6(4): 203–217.
Sources of illustration
• Prawirohatmadjo, S., Suranto, J., Keating, W.G., Ani Sulaiman, & Sosef, M.S.M., 1993. Swietenia Jacq. In: Soerianegara, I. & Lemmens, R.H.M.J. (Editors). Plant Resources of South-East Asia No 5(1). Timber trees: Major commercial timbers. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 442–447.
Author(s)
• R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Based on PROSEA 5(1): ‘Timber trees: Major commercial timbers’.

Editors
• D. Louppe
CIRAD, Dιpartement Environnements et Sociιtιs, Cirad es-dir, Campus international de Baillarguet, TA C-DIR / B (Bβt. C, Bur. 113), 34398 Montpellier Cedex 5, France
• A.A. Oteng-Amoako
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
• M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
General editors
• R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
• L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
• J.R. Cobbinah
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
Photo editor
• E. Boer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Lemmens, R.H.M.J., 2005. Swietenia macrophylla King. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map planted


1, tree habit; 2, flowering twig; 3, sectioned male flower; 4, sectioned female flower; 5, fruit; 6, seed.
Source: PROSEA



tree habit


leaves


bark, leaf and fruits
obtained from University of Hawaii



inflorescence


opened fruit and seeds


opened fruits and seeds


seeds


planks
obtained from Arnhemse Fijnhouthandel



wood (radial surface)


wood in transverse section


wood in tangential section


wood in radial section


transverse surface of wood