4212

5(2): Timber trees; Minor commercial timbers

Durio Adans.

Fam. 2: 399 (1763).

BOMBACACEAE

x = unknown; Durio zibethinus: 2n = 56

Trade groups Durian: lightweight to medium-weight hardwood, e.g. Durio carinatus Masters, Durio graveolens Becc., Durio lowianus Scort. ex King, Durio oxleyanus Griffith, Durio zibethinus Murray.

Durian (general). Malaysia: durian daun (Peninsular). Thailand: thurian (general).
Timber from Coelostegia spp. and Neesia spp. is sometimes also traded under the name durian. Durian timber has been traded as red meranti or in mixed consignments.

Durio consists of about 30 species and is distributed in Burma (Myanmar), Thailand, Peninsular Malaysia, Sumatra, Borneo and the southern Philippines (Palawan). Borneo is the richest in species (about 20 of which 14 are endemic), followed by Peninsular Malaysia (11, 3 endemic) and Sumatra (8, 1 endemic). The "true"" durian (Durio zibethinus) is much cultivated for its fruits from southern India and Sri Lanka, throughout Malesia, to New Guinea, and occasionally outside this area (Australia, Hawaii, Zanzibar).

Durian timber is used for construction under cover; in such conditions it is moderately durable. It is, however, not durable in exposed conditions, but treated durian can be used for door and window frames. Durian is also used for cheaper furniture, cabinets, light-traffic flooring, fittings, panelling, partitioning, plywood, chests, boxes, wooden slippers, low-quality coffins and ship building.
The fruits of Durio zibethinus are much appreciated in South-East Asia because of the highly flavoured and pungent arils around the seeds which are eaten fresh or used for flavouring ice-cream and cakes, or fermented. Several other species also have fruits with edible seed arils. Boiled or roasted seeds are eaten as a snack, whereas young shoots and unripe fruits may be cooked and used as a vegetable. The dried fruit rind is used as fuel, in particular to smoke fish, and the ash is sometimes used for whitening silk and as a lye with dyes. The bark and the seeds are used medicinally. The bark is sometimes used for tanning, and occasionally also for roofing and wall covering.

Durio timber is traded as durian together with timber of the other Bombacaceae genera Coelostegia and Neesia. Durian is exported in fairly large amounts from Sarawak and Sabah, chiefly to Japan, and little from other areas. The total export of durian round logs from Sabah in 1987 was 5300 m³ with a value of US$ 355 000 (US$ 67/m³), and in 1992 it was 8500 m³ (10% as sawn timber, 90% as logs) with a value of US$ 655 000 (US$ 170/m³ for sawn timber, US$ 68/m³ for logs).

Durio yields a lightweight to medium-weight hardwood. The heartwood is pinkish-brown, red to deep red-brown, and usually distinctly demarcated from the whitish to pale yellow-brown or pale reddish-yellow sapwood. The density is 400—750(—850) kg/m³ at 15% moisture content. The grain is straight to interlocked, texture coarse to very coarse and uneven. The wood has a foetid smell when freshly sawn.
At 15% moisture content, the modulus of rupture is 60.5—77 N/mm², modulus of elasticity 9595—12 740 N/mm², compression parallel to grain 35.5—42.5 N/mm², compression perpendicular to grain c. 4 N/mm², shear 4.5—10 N/mm², cleavage 36—37 N/mm radial and 40—46.5 N/mm tangential, Janka side hardness 2685—3210 N and Janka end hardness 3305—3955 N.
The rates of shrinkage are moderately low to moderately high: c. 2.4% radial and 4.0% tangential for Durio oxleyanus wood from green to 15% moisture content, and 3.0—3.5% radial and 4.9—6.6% tangential for Durio carinatus and Durio zibethinus wood from green to oven dry. Durian wood can be air dried fairly rapidly without significant defects, but thin boards should be stacked properly as they tend to cup easily. Boards of Durio oxleyanus wood 15 mm thick take about 3 months to air dry, boards 40 mm thick take 4 months. In Malaysia kiln schedule D is used and durian wood is generally easy and rapid to kiln dry, but boards of Durio oxleyanus wood 70 mm thick take up to 1.5 month to dry. It is recommended to air dry the timber for at least 2 weeks before kiln drying.
Durian wood can be sawn easily, but sometimes the wood surface tends to have a slightly raised grain. Wood of Durio griffithii and Durio wyatt-smithii has been reported to contain silica, which may cause difficulties in sawing. Tests on the machining properties of Durio oxleyanus and Durio zibethinus wood showed good results for planing, shaping and sanding, but only moderate results for boring, mortising and turning. The wood polishes reasonably well, and nails well. It can be peeled to make veneer at a 90° peeling angle without pretreatment. Gluing with urea-formaldehyde produces plywood meeting the German standard. Durian is suitable for manufacturing both structural and utility plywood.
Durian wood is classified as non-durable under tropical conditions. Test sticks of Durio lowianus wood of 50 mm 50 mm 600 mm had decomposed in graveyard tests in Malaysia in 1.7 years. Durio wood is susceptible to dry-wood termite attack. During drying it is prone to powder-post beetle attack. Damage caused by pinhole borers also occurs frequently. The treatability of Durio zibethinus wood with copper-chrome arsenic preservatives using the vacuum-pressure process is classified as moderate to difficult. Wood of Durio oxleyanus, however, absorbed preservatives very readily when soaked in a cold mixture of creosote and diesel fuel.
Durio wood contains 51% cellulose, 24.5—27.5% lignin, 12—15% pentosan and 0.6—1.0% ash. The solubility is 1.4—5.1% in alcohol-benzene, 0.4—2.6% in cold water, 5.3—5.8% in hot water, and 14.8—17.2% in a 1% NaOH solution. The energy value of Durio zibethinus wood is 18 640 kJ/kg.

Small to large trees up to 50(—60) m tall, with straight and cylindrical bole branchless for up to 35 m and up to 120(—140) cm in diameter, buttresses usually present, usually small and rounded to sometimes large, pneumatophores (knee roots) sometimes present in trees growing in marshy places; bark surface smooth or rough, flaky, scaly or fissured, often reddish-brown or dark brown but sometimes greyish or fawn coloured, inner bark pink, deep red, reddish-brown to dark brown; crown spreading and cauliflower-shaped, with large twisting branches. Twigs, inflorescences and leaf undersurfaces more or less densely covered with peltate scales, those on leaf undersurface subtended by stellate hairs which are sometimes exposed owing to absence or paucity of scales. Leaves alternate, simple and entire, generally oblong to elliptical or lanceolate, often copper-brown scaly below, secondary veins usually not prominent, generally curving and joining within the margin; petiole usually slender and swollen towards the apex; stipules present but usually soon shed. Inflorescence consisting of few-flowered cymes on twigs, older branches or bole. Flowers pedicelled, subtended by small or large, persistent or caducous bracts, with epicalyx closed over the bud and splitting into 2 lobes at anthesis; calyx 5-lobed but sometimes splitting into 5 free sepals, the base usually becoming sac-like; petals (4—)5(—6), free, longer than the calyx, white, yellow, pink or red; stamens numerous, free or united into 5 bundles, the bundles themselves free or united at base, each filament bearing 1—many unilocular anthers opening by a slit or an apical pore; ovary superior, sessile, (3—)5(—6)-celled with 2—many ovules in each cell, style 1, long and slender, stigma head-like, small. Fruit a large, woody, globose to ellipsoid capsule covered with spines, usually opening by 5 valves either on the tree or after falling. Seeds in 2 rows in each compartment of the fruit, usually with a prominent aril, with rather thin seed-coat and thick cotyledons. Seedling with epigeal germination ("durian type"") with cotyledons remaining in the seed-coat, sometimes hypogeal, with long sturdy taproot and strongly enlarging hypocotyl, first leaves scale-like, normally developed leaves long-petioled with cuspidate apex, resembling those of mature trees but thinner.

— Macroscopic characters:
Heartwood pinkish-brown, red or deep red-brown, often but not always clearly distinct from the whitish, pale yellow-brown or pale reddish-yellow sapwood. Grain straight to interlocked. Texture coarse to very coarse and uneven. Growth rings absent; vessels visible to the naked eye, tyloses absent; parenchyma not visible to the naked eye, but distinct with a hand lens as diffuse-in-aggregates or fine narrow bands; rays barely visible to the naked eye; ripple marks absent.
— Microscopic characters:
Growth rings indistinct or absent. Vessels diffuse, mostly 1—5/mm², solitary and in short radial multiples of 2—3, round to oval, mostly 240—300 µm in tangential diameter; perforation plates simple; intervessel pits alternate, circular to oval, 6—8 µm; vessel-ray pits similar but half-bordered; tyloses absent. Fibres 0.7—2.0 mm long, non-septate, thin-walled to thick-walled, with simple to minutely bordered pits mainly occurring in the radial walls. Axial parenchyma abundant, predominantly diffuse to diffuse-in-aggregates, or banded resulting from organized diffuse-in-aggregate parenchyma, generally in narrow bands or lines, up to 3 cells wide, reticulate, with 8 or more cells per parenchyma strand. Rays 5—8/mm, 800—2200(—3000) µm high, heterocellular with more than 4 rows of upright and/or square marginal cells, mostly 3—5(—6) cells wide; tile cells present of the same height as the procumbent ray cells ("durio"" type); storied structure absent. Prismatic crystals in non-chambered axial parenchyma cells and in chambered axial parenchyma, generally in short chains of 2—5 chambers, 1 crystal per cell or chamber. Silica usually absent, but small silica bodies observed in axial parenchyma cells in one specimen of Durio oxleyanus.
Species studied: Durio dulcis, Durio lowianus, Durio oxleyanus, Durio zibethinus.

Germination of Durio zibethinus seeds is observed to be "epigeal-like"" when seeds are sown with the micropyle pointing downwards and hypogeal when the micropyle is pointing upwards or when seeds are sown vertically in the soil. The "durian germination"" may be distinguished as a specific and distinctive type. It is characterized by the developing hypocotyl which lifts the seed body well above the ground before shedding it, with the cotyledons still enclosed. Most species have this type of germination, but a few species (e.g. Durio malaccensis and Durio singaporensis) show hypogeal germination with a shoot growing out at one end of the seed and a root from the other end. These latter species show delayed germination, and in their seed the embryo is represented by a swollen hypocotyl filling up the seed; cotyledons and radicle seem to be absent.
In Sabah, the mean annual diameter increment of Durio spp. is 0.3—0.5 cm.
Durio trees grow according to Roux's architectural model, i.e. a monopodial orthotropic trunk which shows continuous growth and has plagiotropic branches. Flowers are borne on the main limbs ("ramiflory"") and when borne on the trunk ("cauliflory"") flowers may even be found at ground level. Flowering is often seasonal, gregarious and regular and for some species twice a year. The flowering intensity of 35 Durio griffithii trees in Peninsular Malaysia in four consecutive years was 60%, 57%, 5% and 89%. This species is self-incompatible and in natural forest only 8% of the flowers were found to be successfully fertilized; hence fruit set is very low. Other understorey species such as Durio acutifolius and Durio malaccensis also flower annually, but the emergent species Durio lowianus and Durio oxleyanus flower only at long intervals, like members of the Dipterocarpaceae. In some species floral initiation occurs 8 months prior to anthesis. Flowering within a tree is usually completed within 2—3 weeks. The flowers often have a sour smell and they usually open in the late afternoon. Ripe fruits usually fall from the trees 13—15 weeks after flowering.
Pollen of Durio zibethinus and Durio graveolens has been found in guano samples from Eonycteris spelaea, a nectarivorous bat, thus indicating that flowers of these species are pollinated by bats. Possibly other Durio species are also truly chiropterophilous. Flowers of Durio griffithii are thought to be pollinated by large insects. The fruits are much sought after by animals (the attraction of wild durian fruits to orang-utans is well-known), which eat the arils and disperse the seeds.

Durio is closely related to Coelostegia and Neesia. Coelostegia differs in the epicalyx not completely covering the flower bud and the calyptriform corolla being shed a whole, while Neesia differs in the fruit wall having irritating hairs inside.
Two subgenera are distinguished: subgenus Durio having anthers dehiscent by a slit, and subgenus Boschia (Korth.) Kosterm. & Soegeng (formerly considered as a separate genus Boschia) having anthers opening by a pore.

Durian occurs in lowland rain forest up to 1000(—1300) m altitude, mostly in lowland dipterocarp forest, sometimes also in swamp forest and kerangas. The trees are usually scattered and uncommon, but some species are locally very common or even gregarious, e.g. Durio carinatus in peat-swamp forest in Peninsular Malaysia and Durio lanceolatus on sandy soils in dipterocarp forest in East Kalimantan. Durio zibethinus is widely cultivated and sources disagree about its occurrence in the wild.

Durian seed usually germinates rapidly, within a few days to a few weeks. As the seed often cannot withstand desiccation or low temperatures and hence cannot be stored, it is considered "recalcitrant"". The following germination rates have been found for fresh seed: 95% in 5—19 days for Durio graveolens, 85% in 8—58 days for Durio griffithii, 100% in 12—21 days for Durio lowianus, 85% (12 out of 14 seeds) in 9—36 days for Durio oxleyanus, and 80—100% in 3—26 days for Durio zibethinus. Some species, like Durio malaccensis and Durio singaporensis have staggered and delayed germination. Durio malaccensis seed was found to have 90% germination in 48 days to over one year and Durio singaporensis had 55% germination in 77 days to almost two years. Different grafting techniques are used to propagate Durio zibethinus when aiming at fruit production.

The Durio species of primary forest occur only scattered; in Peninsular Malaysia an average of 3.7 large trees in 40 ha was found. In a 50 ha plot of lowland forest in Peninsular Malaysia only 10 trees of Durio oxleyanus with a diameter more than 30 cm, and 26 trees of Durio singaporensis with a diameter more than 10 cm were found. The density of Durio griffithii was, however, fairly high in the same plot, i.e. 120 trees of more than 10 cm in diameter. Natural regeneration in the forest is poor, and seedlings occur scattered. Therefore, management systems do not specifically take into account the occurrence and regeneration of durian. Only the species occurring in peat-swamp forest are more abundant, e.g. Durio carinatus, which constitutes 25% of the timber volume of this forest type in Riau, Sumatra. However, natural regeneration of durian in forest in Sarawak is reported as good.

Durio zibethinus trees planted for their fruits may suffer from many diseases and pests; the most serious disease is patch canker caused by Phytophthora palmivora. Certain other species, such as Durio lowianus, have showed resistance to this disease. Nothing is known about diseases and pests of Durio trees planted for timber.

The logs of Durio are often spongy around the pith, which reduces the volume of timber.

In a forest plot in East Kalimantan the estimated timber volume of Durio is 2.9—4 m³/ha.

The logs are susceptible to insect attack and should be extracted from the forest soon after felling. Some logs float in water and can be transported by river.

South-East Asia harbours a wide variety of genetic resources of Durio. However, extensive genetic erosion is reported for cultivated Durio zibethinus in Indonesia, Malaysia and Thailand. Some genetic erosion occurs in wild Durio dulcis, Durio grandiflorus, Durio graveolens, Durio kutejensis and Durio oxleyanus in Indonesia and in wild Durio graveolens and Durio oxleyanus in Malaysia. The trees occur in low density in the forest; this, coupled with the often poor natural regeneration, mean that protection is required. This is also important for improvement of durian cultivated for fruits, and in the future possibly also for timber.

It is known that Durio griffithii is self-incompatible and thus an outbreeder. The wild durians may be very important for breeding currently cultivated species, such as Durio kutejensis, Durio oxleyanus and, particularly, Durio zibethinus.

Although at present Durio contributes comparatively little to the timber industry, there is potential to plant non-clonal material of Durio zibethinus in forest plantations so that financial returns can be obtained from the fruits while waiting for the trees to reach timber size. Preliminary trials of planting durian trees at edges of logged forest have been carried out in Malaysia.

All Nippon Checkers Corporation, 1989. Illustrated commercial foreign woods in Japan. Tokyo. p. 28.
Ashton, P.S., 1988. Manual of the non-dipterocarp trees of Sarawak. Vol. 2. Dewan Bahasa dan Pustaka. Sarawak Branch for Forest Department Sarawak. pp. 56-76.
Burgess, P.F., 1966. Timbers of Sabah. Sabah Forest Records No 6. Forest Department, Sabah. pp. 53-58.
Kochummen, K.M., 1972. Bombacaceae. In: Whitmore, T.C. (Editor): Tree flora of Malaya. A manual for foresters. Vol. 1. Malayan Forest Records No 26. Forest Research Institute Malaysia. Longman Malaysia SDN. Berhad, Kuala Lumpur. pp. 100-120.
Kostermans, A.J.G.H., 1958. The genus Durio Adans. (Bombac.). Reinwardtia 4(3): 47-150.
Malaysian Timber Industry Board, 1986. 100 Malaysian timbers. Kuala Lumpur. pp. 128-129.
Martawijaya, A., Kartasujana, I., Kadir, K. & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 28-32.
Ng, F.S.P., 1991. Manual of forest fruits, seeds and seedlings. Malayan Forest Record No 34. Vol. 1. Forest Research Institute Malaysia, Kepong. pp. 32-33.
Subhadrabandhu, S., Schneemann, J.P.M. & Verheij, E.W.M., 1991. Durio zibethinus Murray. In: Verheij, E.W.M. & Coronel, R.E. (Editors): Plant Resources of South-East Asia No 2. Edible fruit and nuts. Pudoc, Wageningen. pp. 157-161.
Wong, W.C. & Lim, S.C., 1990. Malaysian timbers - durian. Timber Trade Leaflet No 113. Malaysian Timber Industry Board, Kuala Lumpur and Forest Research Institute Malaysia, Kepong. 12 pp.

S.K. Yap (general part, selection of species), A. Martawijaya (properties), R.B. Miller (wood anatomy), R.H.M.J. Lemmens (selection of species)

Durio acutifolius
Durio affinis
Durio carinatus
Durio dulcis
Durio excelsus
Durio grandiflorus
Durio graveolens
Durio griffithii
Durio kutejensis
Durio lanceolatus
Durio lowianus
Durio macrophyllus
Durio malaccensis
Durio oxleyanus
Durio singaporensis
Durio testudinarum
Durio wyatt-smithii
Durio zibethinus

Yap, S.K., Martawijaya, A., Miller, R.B. & Lemmens, R.H.M.J., 1995. Durio Adans.. In: Lemmens, R.H.M.J., Soerianegara, I. and Wong, W.C. (Editors): Plant Resources of South-East Asia No 5(2): Timber trees; Minor commercial timbers. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea

The following species in this genus are important in this commodity group and are treated separatedly in this database:
Durio acutifolius
Durio affinis
Durio carinatus
Durio dulcis
Durio excelsus
Durio grandiflorus
Durio graveolens
Durio griffithii
Durio kutejensis
Durio lanceolatus
Durio lowianus
Durio macrophyllus
Durio malaccensis
Durio oxleyanus
Durio singaporensis
Durio testudinarum
Durio wyatt-smithii
Durio zibethinus