Swietenia macrophylla King

Swietenia macrophylla is a very large tree, reaching a height of 30-40 m and a girth of 3-4 m; in favourable conditions it can reach 60 m high and 9 m girth. Trunk straight, cylindrical, with a buttressed base; bark rough, flaking off in small patches. Leaves paripinnate, up to 60 cm long; leaflets 6-16, ovate, lanceolate, acuminate, slightly oblique, light green or reddish when young, dark green and shining when mature, up to 20 cm long, with 8-12 pale, secondary nerves. Flowers 8 mm across, in narrow supra-axillary panicles about 8-13 cm long and fragrant; petals greenish-white, oblong, 4 mm long, rigidly pointed. Fruit a woody capsule resembling a large inverted club, about 12.5 x 7.5 cm, erect. ‘Swietenia’ commemorates Gerard von Swieten (1700-1772), botanist and physician to Maria Theresa of Austria. The specific name, ‘macrophylla’, means large leaved and comes from Greek words ‘makros’ (large) and ‘phyllon’ (leaf).

Flowering mahogany trees have male and female flowers (about 10 times as many male as female flowers, often only the central flower of a cyme is female), but the flowers of both sexes are similar. Trees are sometimes functionally dioecious. In mixed inflorescences, male flowers open 1st, but self-pollination may occur. Flowering and fruiting are distinctly seasonal. Fruit may be produced once a year, and trees start to produce fruit regularly when about 15 years old. Seeds have a thin, taillike wing that makes them rotate when they fall; they are thus dispersed by wind as far as 500 m from the parent tree.

S. macrophylla grows best on well-drained sites with medium to heavy soils.

S. macrophylla is found in all forest types, from the edge of the pine savannah to the climax rainforest, but mostly in mixed hardwood forest belts, along riverbanks, on deep alluvial soils of considerable fertility. It occurs scattered or in small groups, but densities of more than 4-8 trees/ha are rarely encountered. In tropical America, it is among the pioneer species reoccupying degraded agricultural land. It has been shown that teak is outcompeted by S. macrophylla in a mixed stand. In the Philippines, S. macrophylla is reported to be very firm in wind, resistant to cyclones. The species has some weed potential and may invade native forest communities, especially following disturbance. It should not be planted in close proximity to areas of high nature conservation significance.

S. macrophylla was 1st introduced in India from Belize in 1872. It was chiefly planted at lower altitudes in southern India. The 1st trials in the Solomon Islands were established in 1958 at Vanikolo, with the 1st plantations being established in 1977-78. In 1982, it was established as a major species in the Solomon Islands Planting Programme. In Haiti, S. macrophylla was introduced during the 1940s at Bayeux and Franklin by SHADA (Société Haitienne-Americaine pour le Developement Agricole). There are over 54000 ha of plantations in Indonesia, mainly in West Java. It is nearly extinct in Ecuador, Colombia, Panama, Costa Rica; close to commercial extinction in Bolivia; declining in Mexico, Belize, Brazil; in severe decline in Guatemala, Peru, Nicaragua and Honduras.

Fruiting can sometimes be heavy, and mature trees can produce copious seed crops. Mature fruits can be collected directly from trees by climbing them. Fruit is placed in open trays in a well-ventilated, shaded area and beaten by hand against a hard surface. The seed is separated and the wings gently broken off by hand, then further dried to about 6-8% mc. In Haiti, most farmers who plant out seedlings do so from naturally regenerated stock from the field. No seed pretreatment is required. Germination of fresh seed normally commences 10-17 days after sowing, and the germination rate is high at over 90%.

Young trees are fairly tolerant to shade, but conditions for optimum growth call for full overhead light combined with side protection. In natural stands, therefore, it is beneficial to open the canopy over dense, young regeneration in which saplings are about 1.8 m high. In plantation forestry, S. macrophylla has always been planted at 10 x 3 m (333 stems/ha), because it requires large amounts of light. Plantations established at such wide spacing rarely need thinning unless selectively to remove diseased stems. The tree is self-pruning and further pruning is not necessary. When grown for timber, S. macrophylla has a rotation age of 30-35 years, with a final stocking rate of 150-250 stems/ha.

The most serious pest of S. macrophylla is the seedling shoot borer (Hypsipyla robusta), which is also a plantation pest. Its attack can reach epidemic proportions, resulting in poor bole form and a severe reduction in timber quality. Orthene, a systematic insecticide, has proved an effective chemical control of this pest. Throughout the Greater Antilles, the mahogany web worm, Macalla thyrsisalis, causes defoliation and webbing. In the Caribbean the mahogany shoot borer, Hypsipyla grandella, bores into the buds, shoots and stems of the tree. The coffee tree borer, Apate monachus, attacks both live and dead trees, penetrating deeply into branches, deforming trunks, and making them susceptible to breakage in high winds. In Haiti an unidentified shoot borer, a caterpillar, and the snout beetle, Pachnaeus litus, all attack the tree. The beetle attacks the seed capsules and defoliates the plant. In Puerto Rico, the wet-wood termite Nasutitermes costalis consumes dead branches and occasionally the tree trunks. A less serious problem of ambrosia beetle damage of standing trees has been noticed in Fiji. The scotylid beetle Xylosandrus compactus lays eggs in galleries in the stems of seedlings in the nursery leading to their collapse, it also infests living twigs and branches of older trees. Other minor pests observed in experimental plantings are the leaf-feeding caterpillar Attacus atlas and the leaf cutter bee Megachile sp. Heart and butt rots are common in older trees, apparently entering through basal scars and branch stubs. In Puerto Rico, the leaf blight fungus Phyllosticta swietenia results in defoliation under humid nursery conditions. Diseases of seedling nurseries in Haiti include leaf spot, anthracnose, leaf blister, damping off and stem blight.

Despite widespread suggestions to the contrary, seeds of this species are not recalcitrant but are probably intermediate; 2.5% of seeds germinated following 2 years of hermetic storage with dry seeds at 3-5 deg. C. Viability can be maintained for 1 year in hermetic storage. No loss in viability occurs after storage for 7 months at 12 deg. C with 9% mc. Seeds tolerate desiccation to 5%. There are about 2400 dewinged seeds/kg.

Shade or shelter: S. macrophylla is used as a shade tree, for example, for young plantations of dipterocarps. Reclamation: S. macrophylla has been used in reforestation projects and has proved to be suitable in areas not protected from grazing. Soil improver: The crushed fruit shells have been used as a potting medium. Ornamental: Planted as a lawn tree in peninsular Malaysia. Intercropping: The value of S. macrophylla as an undercrop for teak (Tectona grandis), to facilitate heavy thinning of the latter without exposing the soil to the risk of serious desiccation and erosion, is quite promising and worth great consideration. In Puerto Rico, farmers have planted S. macrophylla among subsistence crops such as corn, beans, bananas, sweet potatoes and cassava.

Timber: The high value attached to S. macrophylla wood in the international markets is well known. The heartwood is red-brown in appearance. The density of the wood of plantation-grown trees is often somewhat less than that of trees from the forest in the natural area of distribution and weighs 485-840 kg/m³ at 12% mc. The wood has been used in interior panelling, joinery work, turnery, furniture, plywood and heavy construction work. Veneer quality is limited by colour variation, wavy grain, pin knots and pinhole borer damage. Gum or resin: A gum is produced from cuts in the bark for markets in Bombay, India, it is marketed in both pure form and mixed with other gums. Tannin or dyestuff: The bark is used for dyeing and tanning leather. Lipids: An oil that might be of some commercial value can be extracted from the seed kernels. Medicine: Various medicinal uses of parts of the tree are reported from Central America.