AgroForestryTree Database
Ochroma pyramidale
 Species identityEcology and distributionPropagation and managementFunctional usesPests and diseasesAdditional InfoBibliographyImages |
Species identity
TaxonomySynonym(s)
Common names
(Trade name) : balsa
Botanic description
Deciduous or evergreen, medium-sized or rarely large trees up to 30(-50) m tall; bole straight, usually short, cylindrical, up to 100(-180) cm in diameter, with short buttresses in older trees; bark surface smooth, grey-white mottled. Leaves arranged spirally, simple, angular-lobate, palmately veined; stipules present. Flowers axillary, solitary; calyx tubular, with 5 unequal lobes; petals 5, whitish; stamens united into a briefly 5-lobed staminal column bearing sessile wavy anthers from the middle to the apex; ovary superior, 5-locular with many ovules in each cell, style club-shaped, stigma spiralled. Fruit an oblong, ribbed, 5-valved dehiscent capsule, densely lanate inside. O. pyramidale is highly variable, which is probably why the genus was formerly thought to comprise at least 11 species. Growth of O. pyramidale trees can be extremely rapid and is according to Koriba's architectural tree model, characterized by orthotropic axes which branch to produce initially equivalent modules. Subsequently one of these modules becomes dominant, constituting one unit of the sympodial trunk.
Ecology and distribution
History of cultivationOchroma is a monotypic genus occurring in tropical Central and South America from southern Mexico to Bolivia. The only species is O. pyramidale (Cav. ex Lamk) Urban which is planted in many tropical countries; in the Malesian region in the Philippines, Malaysia, Java and Papua New Guinea where it has locally become naturalized.
Natural Habitat
O. pyramidale is a typical pioneer, colonizing clearings. It can tolerate a dry season of up to 4 months, but only if the relative humidity does not normally drop below 75%.
Ochroma is a monotypic genus occurring in tropical Central and South America from southern Mexico to Bolivia. The only species is O. pyramidale (Cav. ex Lamk) Urban which is planted in many tropical countries; in the Malesian region in the Philippines, Malaysia, Java and Papua New Guinea where it has locally become naturalized.
Biophysical limitsAltitude: Up to 1000 m; Annual precipitation in natural conditions: 1250-3000 mm; Mean annual temperature: 22-27 deg. C. Soil types: It grows gregariously with a preference for alluvial flats, on rich, well-drained or volcanic soils.
Reproductive Biology
In Java and Peninsular Malaysia O. pyramidale flowers throughout the year and is pollinated by bats. Trees start producing viable seed after (2-)3-4 years and dispersal is by wind.
Propagation and management
Propagation methodsO. pyramidale can be propagated by seed. The very fine seeds (112 000-150 000 dry seeds/kg) should be collected from standing trees. In Papua New Guinea seed is collected in June-August. Seeds can be sown directly in the field or in the nursery. Freshly collected seed has only 10% germination. Seeds contain an impervious testa which must be ruptured by heat (boiling water, fire) before they will germinate. Under natural conditions forest clearance exposes the soil to the sun and this triggers germination of Ochroma seeds. In the nursery seeds are sown in lines 3-4 cm apart under slight shade and in sterilized soil to prevent damping-off. Pretreated seeds show 65-75% germination in 6-28 days and seedlings are pricked out and transferred to containers.Tree Management
Plantation: When seedlings are 3-4 months old and 20-25 cm tall, they can be planted out in the field at 4-5 m x 4-5 m, possibly in a taungya system with a spacing of 2 m x 3 m. In Papua New Guinea a higher initial density of 2268 trees/ha (about 2.1 m x 2.1 m) is applied. As the roots of young plants are extremely sensitive to damage, bare-rooted plants cannot be used and direct seeding is preferred using seed holes at 3 m x 3 m. The soil should be deep, well-aerated and fertile, to allow for rapid growth; slightly inferior sites retard growth and will produce wood with a higher density (over 160 kg/m¦), which is not of commercial interest as only the extremely lightweight wood is in demand. Husbandry: Thinning is comparatively heavy and aims at creating enough growing space for the trees to allow for rapid growth. For Papua New Guinea a reduction of the initial 2268 trees/ha to 99 trees/ha before clear felling at the age of five is advocated. A rotation of 8 years is applied in Indonesia with a reduction in stems from 900-1225 to 90-170 per ha, depending on the site. Great care should be taken to avoid damage to the remaining trees, as they heal very poorly or not at all. A mean annual volume increment of 17-30 m¦/ha can generally be expected, although 69 m¦/ha and 90 m¦/ha has been achieved in Indonesia in 8- and 6-year-old plantations, respectively and 50 m¦/ha is commonly accepted as realistic. Rotations do not generally exceed 7-8 years, as the rapid growth slows down appreciably after 7-12 years. At this age heartwood development starts with a much higher density and a darker colour rendering it less suitable for the special purposes. After harvest, residues can be burnt, which gives rise to abundant natural regeneration.
Germplasm Management
The very fine seeds (112 000-150 000 dry seeds/kg) can be stored for several years in jute bags or in closed receptacles.
Functional uses
ProductsFibre: For the production of pulp and paper. Ropes have been made from the fibrous bark. Timber: The extremely lightweight wood of Ochroma is used for buoys, life-jackets and life-belts, surf boards, aircraft construction, toys, model making, entomology mounting boards, core stock in sandwich construction, surgical splints, packaging of fragile articles and as insulation for heat, vibration, sound and formerly also for electricity. The heavier wood of Ochroma is suitable for matches, popsicle sticks, toothpicks, etc. Other products: The kapok from the fruits is suitable for filling pillows and mattresses.Services
Ornamental: The tree is sometimes planted as an ornamental. Shade or shelter: The tree is sometimes planted as provide shade expediently.
Pests and diseasesPests: Zeuzera coffeae, a wood borer, has been observed in a 1.5-year-old plantation in Java seriously damaging the majority of trees which had to be clear felled to avoid attack of other trees.
Additional Information
DevelopmentIn Peninsular Malaysia growth is too slow to produce the very low-density wood which is sought after for many of its uses. In trials in Indonesia the mean annual increment was 2.0-6.6 cm in diameter and 1.2-3.3 m in height. In Papua New Guinea trees with a diameter of about 20 cm displayed a mean annual diameter increment of 1.7-4.3 cm. In South America mean annual diameter increment is even up to 10 cm and after 10-12 years, when growth stabilizes, trees are generally 20-25 m tall and about 100 cm in diameter. After 12-15 years growth slows down and the trees deteriorate rapidly. Only under specific circumstances may trees reach 50 m in height.Properties
Timber (paragraph 1): Ochroma is an extremely lightweight hardwood with a density of (40-)90-310 kg/m cubic at 12% moisture content, but with a very large difference between the outer most wood and that from the centre, the new wood being on average 2.2 times heavier than the old wood as determined for wood samples from Costa Rica. Most of the commercial stock is sapwood. Heartwood white to grey-white, sometimes with a pinkish tinge near the heart in older trees, not clearly demarcated from sapwood; grain straight; texture coarse and even; wood with silky lustre. Test in Papua New Guinea at 13% moisture content showed the following mechanical properties: modulus of rupture is 8.5-12.5 N/mm cubic and modulus of elasticity 1155-1645 N/mm cubic. Test in the Philippines at green condition showed the following mechanical properties: modulus of rupture is 31 N/mm cubic, modulus of elasticity 4605 N/mm2, compression parallel to grain 16.5 N/mm cubic, compression perpendicular to grain 2.5 N/mm cubic and janka end hardness 1625 N. At 12% moisture content, modulus of rupture is 56.5 N/mm cubic, modulus of elasticity 6410 N/mm cubic, compression parallel to grain 23.5 N/mm cubic, compression perpendicular to grain 5 N/mm¦ and janka end hardness 2410 N. Timber (paragraph 2): Growth rings indistinct; vessels moderately small to moderately large, solitary and in radial multiples of 2-3, rarely more than 4, open, vessels lines conspicuous appearing as coarse brown scratches; parenchyma paratracheal mostly vasicentric, and apotracheal diffuse-in-aggregates, indistinct; rays medium-sized to moderately broad, conspicuous on all surfaces producing a silver grain on the radial surface; ripple marks absent. Timber (paragraph 3): Shrinkage upon seasoning is low to moderate, the wood seasons easily and rapidly (air drying from green to 15% moisture content takes 1-3 weeks) with very little degrade, but is highly prone to blue stain. It should be converted rapidly after felling to prevent extensive splitting and staining. Kiln drying is preferable to air drying, to minimize splitting and warping; kiln schedule H is recommended. The wood is very soft and very weak but with a good strength to weight ratio. The wood from old trees tends to be brittle. The rates of shrinkage from green to 15% moisture content 0.4-0.6% radial and 2.4-3.9% tangential, and from green to oven dry 1.0-1.5% radial and 4.4-5.3% tangential. Timber (paragraph 4): The wood is very easy to work with hand and machine tools, but sharp tools are essential to prevent crumbling. It has good insulating properties and high buoyancy. The wood is non-durable and prone to attack by Anobium, Lyctus, termites and longhorn beetles. Both sapwood and heartwood are permeable to impregnation, the retention of preservative by the pressure heating method is about 560 kg/m¦ for sapwood and about 334 kg/m¦ for heartwood. Fibre: The fibres are very long and yield a high-quality chemical pulp with a recovery ratio of 45-50%, whereas the raw pulp can be easily bleached.
Trade
Ecuador is the main exporting country of Ochroma wood supplying 80-90% of the volume traded on the world market.
Genetic
Genetic resources and breeding: Differences in wood density in Ochroma may be a starting point for further selection and breeding.
Prospects
O. pyramidale has lost some importance due to the increased use of synthetic materials, but it will probably remain the best material for some special applications, e.g. model making. Increased use for such special applications and for pulpwood is possible.