6228

5(3): Timber trees; Lesser-known timbers

Sapium P. Browne

Civ. nat. hist. Jamaica II: 338 (1756).

EUPHORBIACEAE

x = 11; S. baccatum: n = 22, S. insigne (Royle) Benth.: n = 22 (+ 0-3B), S. sebiferum: n = 44

Ludai (trade name). Malaysia: gurah (Peninsular, Sarawak).

Sapium is a pantropical genus and comprises about 100 species, most of which occur in South America, and the rest in Africa and Asia. Some 6 species are present within Malesia and 1 other (S. sebiferum) has been introduced into the region.

The soft and non-durable wood of Sapium is suitable for temporary construction, boxes and crates, small tool handles, and as core veneer in the production of plywood. It is also suitable for making particle board. When mixed with other species, the pulp is suitable for the production of writing paper. The wood of S. sebiferum yields a good quality fuel.
The mealy but very sweet fruits of S. baccatum are edible. These fruits and those of S. discolor are used in Peninsular Malaysia for baiting traps set for mousedeer. In Taiwan logs of S. discolor are an important medium for shiitake mushroom cultivation. S. sebiferum is well-known because its seed-coat yields tallow that can also be used to manufacture soap, and the seed is a rich source of "stillinga oil"" used as an illuminant and which may be used as a substitute for tung or linseed oil. The leaves of S. sebiferum have been used to dye silk black. The male flowers are important for the production of honey and pollen. The trees are planted as ornamentals and are considered useful in India for stabilizing the banks of streams and rivers. In China they are also interplanted with tea. In Texas, United States, the white seeds are used in decorative flower arrangements. A disadvantage is that S. sebiferum can be an aggressive weed, which is easily spread by birds and difficult to eradicate as it sprouts profusely from stumps and is highly resistant to herbicides.

The wood of Sapium is seldom used but may reach the market only in mixed consignments of lightweight hardwood.

Sapium yields a lightweight hardwood with a density of 285-470 kg/m³ at 15% moisture content. Heartwood pale yellow-brown, not clearly differentiated from the sapwood; grain straight to deeply interlocked, occasionally wavy; texture moderately coarse and even; longitudinal faces dotted with numerous latex traces. Growth rings sometimes distinct, indicated by darker and denser tissue; vessels medium-sized to moderately large, solitary and in radial multiples of 2-4, conspicuously open; parenchyma moderately abundant, apotracheal in narrow bands to diffuse-in-aggregates, usually visible to the naked eye; rays very fine or moderately fine, visible with a hand lens; ripple marks absent; latex traces may be mistaken for radial latex canals.
Shrinkage upon air drying is low. Air drying is fairly rapid, 13 mm thick boards take about 2 months and 38 mm thick boards about 3 months. Major degrade during seasoning can be caused by moderately severe insect attack and stain, whereas bowing during seasoning is only slight. The wood is soft and weak. S. baccatum is easy to saw and plane, giving a smooth surface; S. luzonicum is reportedly very difficult to saw, as the tough fibres clog and pinch the saw and crystals easily dull the saw blade. The wood is non-durable under exposed conditions, but it is extremely easy to impregnate both heartwood and sapwood. In an experiment using different open tank methods and a 50/50 mixture of creosote and diesel, cold soaking gave an absorption of 73 kg/m³, whereas hot soaking at different temperatures yielded figures between 115 and 354 kg/m³. The sapwood is susceptible to Lyctus.
The gross energy value of the wood is 17 300-17 900 kJ/kg. The latex is irritant and blisters the skin.
See also the tables on microscopic wood anatomy and wood properties.

Deciduous, monoecious, small to medium-sized trees up to 30(-39) m tall; bole columnar to sinuous, up to 60(-95) cm in diameter, sometimes fluted at base, sometimes with steep buttresses; bark surface smooth to finely cracked, greyish, in S. baccatum becoming coarsely fissured and dark brown with age, inner bark finely fibrous, often yellowish-brown, with or without white latex. Leaves arranged spirally, simple, entire to serrate; petiole with 2 glands at apex, red; stipules minute. Flowers in an axillary or terminal simple spike or raceme of spikes, male or female ones in different inflorescences or with a few female flowers at base of the otherwise male spike; calyx small, 2-3-lobed; petals absent; disk absent. Male flowers fascicled; stamens 2-3, free or shortly connate; pistillode absent. Female flowers solitary; ovary superior, 2-3-locular with 1 ovule in each cell, styles basally connate, stigmas entire. Fruit a small, woody or leathery capsule dehiscing into 4-6 parts often leaving the central column. Seed black, with a thin, fleshy sarcotesta. Seedling with epigeal germination; cotyledons emergent; hypocotyl elongated; first pair of leaves opposite, subsequent ones arranged spirally.
Sapling growth of S. discolor is intermittent; at the end of the season the leading shoot dies back and one or two of the variably whorled twigs take its place, thus leading to a seemingly dichotomous branching pattern. This tree shape is according to Koriba's architectural model. In India a mean annual diameter increment of 0.8-1.7 cm has been recorded for S. sebiferum; early growth may be very rapid, plants attained 12 cm in diameter and 4.8 m in height after only 3 years and 9 months. In Peninsular Malaysia a mean annual diameter increment of 1.2-1.6 cm has been recorded for S. baccatum. An annual production of 22-26 m³/ha in a 4-year rotation has been recorded for firewood plantations in Texas, United States. In Peninsular Malaysia S. baccatum flowered in April-May though not in all years of observation, but fruits never developed. It produced new leaves in February-April and sometimes also in July-September. S. discolor renews its leaves after a pronounced dry spell. Birds and mammals eat the sarcotesta of the seeds and thus disperse them.
The generic boundaries between Sapium and related genera (e.g. Excoecaria) are not very clear, and various taxonomic publications treat some of the species mentioned here in various other genera. The delimitation followed here represents a conservative view.

Sapium species are scattered in well-drained primary and secondary, evergreen to deciduous rain forest, up to 800(-1800) m altitude.

Sapium can be propagated by seed or by cuttings. For S. sebiferum 8300-8500 seeds/kg and 1-3 seeds/fruit have been reported. Seeds of S. baccatum have only about 5% germination in 54-95 days. Seeds stored in sealed containers remain viable for at least two years. Germination of S. baccatum is inhibited by dense shade; the seeds remain viable in the soil for at least 6 months. S. sebiferum is frost-hardy in India, coppices well, produces root suckers and is not grazed by cattle.

Thanks to their extensive area of distribution, none of the Sapium species except S. luzonicum seems in danger of genetic erosion; the latter has been depleted in the Philippines by deforestation.

Sapium may be increasingly planted to serve various purposes, including firewood, but its use as sawn timber is likely to decrease. The aggressive nature of S. sebiferum discourages its use.

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[163]Burkill, I.H., 1966. A dictionary of the economic products of the Malay Peninsula. 2nd edition. Ministry of Agriculture and Co-operatives, Kuala Lumpur. Vol. 1 (A-H) pp. 1-1240. Vol. 2 (I-Z) pp. 1241-2444.
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Purwaningsih

Sapium baccatum
Sapium discolor
Sapium luzonicum
Sapium sebiferum

Purwaningsih, 1998. Sapium P. Browne. In: Sosef, M.S.M., Hong, L.T. and Prawirohatmodjo, S. (Editors): Plant Resources of South-East Asia No 5(3): Timber trees; Lesser-known 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:
Sapium baccatum
Sapium discolor
Sapium luzonicum
Sapium sebiferum