27

5(2): Timber trees; Minor commercial timbers

Azadirachta A.H.L. Juss.

Mirb. & Cass. apud Guill., Bull. Sci. Nat. Géol. 23: 236 (1830).

MELIACEAE

x = unknown; Azadirachta indica: n = 14, 2n = 28, 30

Trade groups - Sentang: lightweight to medium-weight hardwood, Azadirachta excelsa (Jack) Jacobs.
- Neem: moderately heavy hardwood, Azadirachta indica A.H.L. Juss.

- Sentang. Indonesia: kayu bawang (general), surian bawang, bawang kunyit (Kalimantan), nibwak (Irian Jaya). Malaysia: limpaga (Sabah), ranggu (Sarawak). Papua New Guinea: azadirachta. Philippines: maranggo (general), bird's-eye kalantas (En), danggo (Tag.). Thailand: thiam, sadao-thiam.
- Neem: nim, margosa, cornucopia (En), azadirac de l'Inde, margosier, margousier (Fr). Indonesia: imba, mimba (Java), membha, mempheuh (Madura), intaran (Bali). Malaysia: baypay, mambu, veppam (Peninsular). Singapore: kohumba, nimba, veppam. Burma (Myanmar): tamaka, bowtamaka, tamabin. Laos: ka dao. Thailand: khwinin (general), sadao (central), saliam (northern). Vietnam: s[aaf]u d[aa]u.

Azadirachta comprises 2 species. Azadirachta excelsa is native to Peninsular Malaysia, Sumatra, Borneo, Sulawesi, the Aru Islands, New Guinea, and the Philippines. Azadirachta indica is thought to be native to the dry forest areas of the Indo-Pakistan subcontinent and possibly also to Burma (Myanmar). It is widely cultivated, also as a plantation tree, and sometimes occurs naturalized throughout India, Pakistan, Sri Lanka, Thailand and Indonesia. More recently it has also been planted in Peninsular Malaysia and Singapore, the Philippines, Hawaii, Fiji, Australia, Saudi Arabia, tropical Africa, the Caribbean, Central and South America, and the southern United States.

Sentang wood is valued for light construction (under cover) and is used for joinery, furniture, interior finishing, panelling, partitioning, sliced veneer, flooring, turneries, and matches. In the Philippines sentang is also used for piano cases, matches, decorative engraving and cigar boxes, while in Papua New Guinea other applications include louvred doors and canoe making. In Peninsular Malaysia the young shoots, leaves, and flowers are consumed as a vegetable.
Neem wood is appreciated for making carts, agricultural implements, doors, panels, window frames, poles and other building materials, toys and idols. The wood may be used for furniture. Neem is of limited value for construction, as the logs are too short. However, it is considered suitable for the manufacture of plywood and is used as a substitute for mahogany (Swietenia) in Central America. It is a promising, fast-growing source of fuelwood.
Neem seeds and leaves, and reputedly also the flowers and bark, yield azadirachtin which is used as insect and nematode repellent. The oil from the seeds is used for the manufacture of soap, as fuel for lamps and as a lubricant for machinery. The pulp surrounding the seeds is reputedly a promising substrate for generating methane gas. The oil extracted from the bark is industrially used in the manufacture of soap, toothpaste, and pharmaceutical and cosmetic products.
Various parts of neem have medicinal properties used against a wide variety of illnesses. Neem oil has contraceptive properties and is used in local medicine against e.g. malaria, skin diseases, stomach ulcers, worms and rheumatism. Neem is planted as a wayside tree for shade, and in windbreaks. In addition, the young leaves and young flowers are sometimes used as vegetable and the leaves and twigs are used as fodder for sheep and goats, and for mulching and fertilizing. Neem cake, the residue left after extracting oil from the seeds, is reportedly an excellent fertilizer and has potential as an insecticide. The bark contains tannin. Neem is regarded as a highly valuable multipurpose tree with great potential.

Most Azadirachta timber is used locally. Japan imports small amounts of sentang from Papua New Guinea, Sabah and Sarawak. Sentang accounts for about 1% of the total timber import in Japan from Papua New Guinea. In 1987, the export of sentang round logs from Sabah was about 2000 m³ with a value of US$ 135 000 (US$ 68/m³). At present, sentang is often traded in Sabah together with the wood of other Meliaceae genera, such as surian (Toona). The sawn timber export of this combined trade group was slightly less than 100 m³ in 1992, with a value of US$ 33 000 (US$ 360/m³).

Sentang is a lightweight to medium-weight hardwood. The heartwood is pale reddish-brown to dark reddish-brown and distinctly demarcated from the yellowish-white, greyish-white or sometimes grey-pink sapwood. The density is 550-780 kg/m³ at 15% moisture content. The grain is slightly to moderately interlocked, texture moderately coarse to coarse and often uneven.
The following mechanical properties are the result of testing the wood of 5-year-old trees that were 4-6 m tall and 10-12 cm in diameter and had been grown in Thailand, at 10.5% moisture content: the modulus of rupture 94 N/mm², modulus of elasticity 9770 N/mm², compression parallel to grain 52 N/mm², shear 16 N/mm² and Janka side hardness 3980-4050 N.
The rates of shrinkage of sentang reportedly vary from low to moderately high: in Malaysia it is reported to shrink only c. 0.5% radial and 0.5% tangential from green to 15% moisture content, but in the Philippines shrinkage from green to 15% moisture content is reported as c. 2.2% radial and 4.3% tangential, and from green to oven dry 4.5% radial and 7.5% tangential. The timber air dries fairly rapidly with little degrade. Air drying takes approximately 2 months for boards 15 mm thick, and about 4 months for boards 40 mm thick.
Sentang wood is generally easy to work, taking a good finish. The boring are rated as good, and planing and shaping as moderately good. Tests in Sabah showed that the timber peels well without pretreatment; the veneer dried well without serious degrade.
The heartwood of sentang is rated as non-durable to moderately durable. The sapwood is susceptible to dry-wood termites and powder-post beetles, and also to fungal attacks.
Sentang wood contains 45% cellulose, 27% lignin, 16% pentosan and 1.0% ash. The solubility is 2.3% in alcohol-benzene, 2.4% in cold water, 6.6% in hot water and 21.4% in a 1% NaOH solution.
Neem is a moderately heavy hardwood. The heartwood is reddish, becoming reddish-brown upon exposure, distinctly demarcated from the greyish- white sapwood. The density is 720-930 kg/m³ at 12% moisture content. The grain is interlocked, texture coarse.
Tests on trees planted in India and Sudan showed the following mechanical at 12% moisture content: the modulus of rupture 79-99 N/mm², modulus of elasticity 6960-8765 N/mm² and compression parallel to grain 46-51 N/mm².
The rates of shrinkage are moderate: from green to oven dry c. 4.5% radial and 6.2% tangential. The timber seasons well with little degrade. Pre-boring is necessary when nailed.
Neem is generally stronger and more durable than sentang; it is more resistant to termite, powder-post beetle and fungal attacks and even durable under exposed conditions. The energy value of neem wood is 20 830 kJ/kg.
Neem seeds contain up to 40% oil. The bark contains 12-15% tannins. The insecticidal substance is probably azadirachtin.

Small to medium-sized or fairly large, deciduous or evergreen trees, up to 40(-50) m tall; bole cylindrical, buttresses absent or minor, up to 125(-150) cm in diameter; bark surface smooth, becoming fissured and shaggily flaky, pinkish-brown or pinkish-grey, becoming pale brownish or greyish buff in old trees, inner bark orange-red. Indumentum of simple hairs. Leaves alternate, imparipinnate, with 2 pairs of glands at the base of the petiole; leaflets alternate below and opposite to subopposite above, lanceolate to elliptical, reduced in size towards each end of the rachis, with an entire or serrate margin, glabrous.
Flowers in axillary, many-flowered panicles, bisexual and male flowers on the same individual, actinomorphic, 5-merous, fragrant; calyx with imbricate lobes; petals free, imbricate; stamens 8(-)10, filaments united to form a cylindrical staminal tube with (8-)10 small apical appendages, anthers sessile, free, 2-celled, basifixed, inserted opposite to the appendages; disk annular, fused to the base of the ovary; ovary superior, 3-locular, with (1-)2(-3) axillary ovules in each cell, style single, stigma capitate, 3-lobed. Fruit drupaceous, ellipsoid, 1(-2)-seeded, green turning yellow when ripe. Seed ovoid, with a thin membranous testa, with a small adaxial sarcotesta, smelling of garlic when cut; cotyledons unequal. Seedling with phanerocotylar germination, eophylls opposite, trifoliolate; leaflets deeply incised, pinnatifid, or partite.

- Macroscopic characters: Heartwood pale to medium-brown or reddish-brown, sapwood greyish-white, pale brown to slightly yellowish-brown. Grain slightly to strongly interlocked. Texture moderately coarse; wood usually lustrous. Growth rings indistinct or sometimes distinct (Azadirachta indica); vessels medium-sized, visible to the naked eye, often occluded with dark deposits, tyloses indistinct; tangential bands of parenchyma indistinct; rays almost invisible to the naked eye; ripple marks absent.
- Microscopic characters: Growth rings absent or occasionally distinct (Azadirachta indica) and then defined by differences in pore size, fibre wall thickness and initial parenchyma. Vessels diffuse, 4-17(-60)/mm², of 2 sizes, small vessels vasicentric or in terminal clusters in wood specimens having growth rings, larger vessels 4-10/mm², solitary or in multiples or clusters of 2-4 to more than 10, uniformly distributed or occasionally in loose tangential series, generally oval, polygonal in clusters, average tangential and radial diameter of large vessels 105-140 µm and 90-165 µm, respectively (maximum tangential and radial diameter 175-230 µm and 175-285 µm, respectively), average tangential and radial diameter of small vessels 20-35 µm; walls 2-6 µm thick; perforation plates simple; intervessel pits dense and alternate, 3-5 µm; vessel-ray pits similar but half-bordered, 3-4 µm; brown or blackish deposits present; tyloses absent. Fibres 0.8-1.5 mm long, non-septate, 7-25 µm in tangential diameter, thick-walled (3-4 µm), with sparse slit-like pits mainly in the radial walls. Axial parenchyma paratracheal, vasicentric; apotracheal parenchyma in irregularly spaced tangential bands of 3-8 cells wide, strand length 4-20 cells or more. Rays mostly (more than 85%) multiseriate, 2-3 cells wide, up to 550 µm high, heterocellular with 1(-2) rows of square to upright marginal cells, uniseriate rays few, short, mostly less than 150 µm high. Prismatic crystals present in non-chambered apotracheal parenchyma cells. Silica bodies absent. Intercellular canals absent.
Species studied: Azadirachta excelsa, Azadirachta indica.

Sentang trees in Indonesia were 19-24 m tall after 9 years with a bole diameter of 22-27 cm. In Thailand, planted trees reached a diameter of up to 30 cm in 5 years. The growth of neem trees varies greatly, depending on site conditions and provenance. At first, seedlings grow slowly, reaching 15-25 cm tall after one year, but thereafter growth is much faster and trees may reach a height of 4-7 m after 3 years and 5-11 m after 5 years. Under moderate conditions mean annual diameter growth is 0.7-1.0 cm, but under optimal conditions 2 cm may be reached. In irrigated plantations in India, 16-year-old trees reached a diameter of 40 cm.
Neem trees may already start flowering and fruiting at the age of 4-5 years. They can live for over 200 years. The flowering and fruiting season varies greatly with location and habitat. In Thailand, Azadirachta indica trees flower in December to February and fruit in March to May, whereas Azadirachta excelsa flowers in February to March. Fruits ripen in about 12 weeks after anthesis and are eaten by bats and birds.

Azadirachta belongs to the subfamily Melioideae and the tribe Melieae, and is closely related to the genus Melia. It is sometimes confused with the latter but is easily distinguished by its simple pinnate leaves with a pair of orbicular glands and a pair of elongated glands at the base and by the 3-locular ovary, whereas Melia possesses 2-3-pinnate leaves with one pair of orbicular glands and a 4- 8-locular ovary.

Sentang usually grows in secondary forest, but is also found in dipterocarp rain forest where it is associated with Durio, Palaquium, Calophyllum and Agathis species. It occurs scattered in lowland forest, up to 350 m altitude.
Neem has a wide climatic adaptability. It grows in tropical and subtropical regions, from sea-level up to 1500 m altitude. In its natural habitat in India it is generally found in mixed forest in association with Acacia spp. and Dalbergia sissoo Roxb. ex DC. In Indonesia, where it occurs widely naturalized, it is usually found in lowland monsoon forest and is associated with e.g. Acacia leucophloea (Roxb.) Willd., Albizia chinensis (Osbeck) Merr., Butea monosperma (Lamk) Taubert, and Cassia fistula L. Optimal growth is observed in areas with an annual precipitation of around 1000 mm, but neem plantations can be established in areas with only 450-750 mm of rain. Neem tolerates some frost. It does not like inundation and does not tolerate waterlogging. Neem is a light demander, but tolerates fairly heavy shade during the first few years. It grows on a wide variety of neutral to alkaline soils, but performs better than most species on shallow stony, sandy soils, or in places where there is a hard calcareous or clay pan not far below the surface. It grows best on soils with a pH of 6.2-7.0.

Sentang and neem are generally propagated by seed, but can also be propagated by air layering, root and shoot cuttings, grafting and tissue culture.
Fruits should be collected off the trees to avoid contamination by soilborne pathogens and should not be placed directly on the ground. Fruits can be depulped by washing and seeds are air dried for 3-7 days in a dry and shaded area before being stored. Depulped fruits should be 'density graded' by being put in water; any 'floaters' should be discarded. Neem seeds remain viable for about 4-8 weeks only, but storage of dried seeds at 15 °C will prolong this period up to 4 months. Depulped fruits stored at -20 °C retained their viability for as long as 10 years. The germination rate for neem and sentang is 75-80% when seeds are sown directly after being harvested, and 50-60% when sown after being stored. However, when stored for 3 months under ambient conditions the germination rate of neem seed is only 8%. Azadirachta excelsa has about 470 seeds/kg and Azadirachta indica 3700-5400 seeds/kg. No seed treatment is required, although speed and rate of germination are increased when seeds have passed through the intestines of ruminants.
Seeds are sown in seedbeds, polybags or root-trainers. Spacing in seedbeds is 20 cm between the rows and 5 cm within the row, and seeds are covered with 0.5-1 cm soil. Germination starts 1-3 weeks after sowing. During germination, light shade is recommended; it should be maintained for about 2 months.
Seedlings can be transferred to containers (polybags) when two pairs of leaves have developed. The seedlings should be provided with at least 50% shade at first and gradually exposed to full sunlight when about 30 cm tall. Seedlings can be planted out in the field 12 weeks after sowing when the stem is 7.5-10 cm long with a taproot of 15 cm, either as bare-rooted plants or as plants from polybags. The taproot of bare-rooted seedlings should be pruned before planting. Stumps and striplings are generally made from one-year-old seedlings; for stumps the roots are pruned to 20 cm and the shoot to 5 cm. Seedlings with a well developed root system, such as those raised in root-trainers or through fertilization in the nursery, can withstand drought better and show a higher survival rate.
In Thailand, wildlings of Azadirachta spp. had a survival rate of 85% when planted out immediately after collection.
Vegetative propagation by cuttings is possible and over 90% rooting was obtained when cuttings were taken from coppicing shoots. However, this is not recommended for semi-arid areas, as the taproot will not develop. This also holds true for air layering, where mainly lateral roots are formed. Rootlets of 0.3-0.5 cm diameter and 3-5 cm long have been used successfully in Thailand as propagules.
Direct seeding in well prepared soil on well-drained sites is possible by sowing the seeds at a depth of 1.5 cm and at a spacing of 3 m x 3 m. In taungya systems spacing may be as close as 1.3 m x 1.3 m. The seedlings that issue from direct sowing, however, develop more slowly than those raised in the nursery.
Sentang is planted at a spacing of 2-4 m x 4 m; in Sumatra the local population has planted sentang using seedlings collected from the forest. Sentang and rubber are often mixed in plantations.

Natural regeneration of neem is usually profuse, as the seeds are widely distributed by bats and birds. In dry areas, it is essential to weed neem plantations, as neem cannot withstand competition, especially from grasses. Rotation of neem plantations for firewood in West Africa is 7-8 years at a final spacing of 5 m x 5 m. In Haiti, on good soils and with adequate moisture, it is planted at 2.5 m x 2.5 m and managed with a rotation of only 4 years.
As neem coppices well, no replanting is necessary after harvesting. Coppicing is also preferred from the point of view of fuelwood production, as it facilitates the harvesting and managing of the plantation. Neem withstands pollarding well, a valuable asset for its use in windbreaks. Sentang also coppices well and coppice shoots grow faster than shoots from seedlings.
Leaf litter of neem is reported to raise the pH of the soil surface from 5 to 7.

There are no records of fungi attacking neem in South-East Asia.
Hypsipyla robusta, a shoot borer and a serious pest in many Meliaceae has not been recorded for Azadirachta. Neem has few serious pests, but several scale insects have been reported to infest it, e.g. Aonidiella orientalis (feeding on sap of young branches and young stems), which is the most important pest, and Pulvinaria maxima (feeding on sap, and covering tender shoots and stems). The nymphs of Helopeltis antonii are also found to feed on sap. It has been observed that rats and long-spine porcupines attack and occasionally kill neem seedlings and trees, by gnawing the bark around the base.
Mistletoes infesting neem are Dendrophtoe falcata and Tapinanthus sp.
A serious decline of neem has been observed in West Africa recently. Older foliage is shed, leaving crowns with an open appearance. Tufts of leaves remain at the branch apices, for which the disorder is now known as 'giraffe neck'. Preliminary conclusions indicate that neem decline is not caused by a biotic agent, but is due to site-related stress such as inadequate soil moisture, soil compaction, competition, and intercropping.

In Thailand, the first harvest of sentang is usually 5 years after planting, when the stem is 20-30 cm in diameter.

Plantations of sentang on Java with a spacing of 2.5 m x 4 m yielded 12 m³/ha of wood annually in the first 10 years. The form factor was assessed at 0.4. Plantations of neem in Thailand with spacings of 2-4 m x 4 m yielded 6-7.5 m³/ha annually in the first 10 years on poor sites and 33-36 m³/ha annually on favourable sites, the slightly lower yields being recorded for the wider spacing. In West Africa, fuelwood plantations managed with a rotation of 8 years and with an initial spacing of 2.4 m x 2.4 m yielded 2.5-21 m³/ha annually.

Sentang wood is subject to fungal attack and needs to be treated when used outdoors. Neem wood is very resistant to insects and fungi and does not require treatment with preservatives.

As neem and sentang are widely distributed, considerable genetic variation may be expected. Neem is much planted and naturalized throughout South-East Asia, but sentang is more rarely planted; the latter is only locally cultivated in botanical gardens and experimental gardens, e.g. in West Java (especially provenances from Sulawesi). In Thailand, 42 seed provenances of neem have been identified throughout the country.

Phenotypically superior neem trees have been clonally propagated in India and Thailand. Fresh cotyledons were found to be the best source of material for tissue culture.

Sentang and neem seem to have good prospects for use in timber plantations, e.g. as a substitute for mahogany (Swietenia spp.) for plywood and cabinet making. Neem is also interesting as a multipurpose tree in agroforestry and for reforestation purposes especially on critical soils and in drier areas. More research is needed on the silviculture of sentang, which is a very fast-growing tree.

Mabberley, D.J. & Pannell, C.M., 1989. Meliaceae. In: Ng, F.S.P. (Editor): Tree flora of Malaya. A manual for foresters. Vol. 4. Forest Research Institute Malaysia. Longman Malaysia SDN. Berhad, Kuala Lumpur. pp. 231-233.
Malaysian Timber Industry Board, 1986. 100 Malaysian timbers. Kuala Lumpur. pp. 194-195.
Mitra, C.R., 1963. Neem. M.S. Patel, Hyderabad. 190 pp.
National Academy of Sciences, 1980. Firewood crops - Shrub and tree species for firewood production. National Academy of Sciences, Washington D.C. pp. 114-117.
Ponnuswamy, A.S., Vinaya Rai, R.S., Surendan, C. & Karivaratharaju, T.V., 1991. Studies on maintaining seed longevity and the effect of fruit grades in neem (Azadirachta indica). Journal of Tropical Forest Science 3(3): 285-290.
Radwanski, S.A. & Wickens, G.E., 1981. Vegetative fallows and potential value of the neem tree (Azadirachta indica) in the tropics. Economic Botany 35(4): 398-414.
Ruskin, F.R., 1992. Neem: a tree for solving global problems. National Research Council. National Academy Press, Washington D.C. 141 pp.
Somyos Kijkar, 1992. Handbook: Planting stock production of Azadirachta spp. at the ASEAN-Canada Forest Tree Seed Centre. ASEAN-Canada Forest Tree Seed Centre Project, Muak-Lek, Suraburi, Thailand. 20 pp.
Tampubolon, A.P. & Alrasyid, H., 1989. The neem tree and its developmental prospect in rainfed zones in Indonesia. Duta Rimba 15(109-110): 8-12.
Tewari, D.N., 1992. Monograph on neem (Azadirachta indica A. Juss.). R.P. Singh Gahlot for International Book Distributors, Dehra Dun. 279 pp.

B. Sunarno (general part, properties), N. Tonanon (properties) & S. Noshiro (wood anatomy)

Azadirachta excelsa
Azadirachta indica

Sunarno, B., Tonanon, N. & Noshiro, S., 1995. Azadirachta A.H.L. Juss.. 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:
Azadirachta excelsa
Azadirachta indica