Streblus (PROSEA Timbers)

Plant Resources of South-East Asia Introduction

List of species

Streblus Lour.

Protologue: Fl. cochinch.: 614 (1790).

Family: Moraceae

Chromosome number: x= 13, 14; S. asper: 2n= 26, S. indicus (Bureau) Corner: n= 14

• Tempinis (trade name)
• Thailand: khoi (general)
• Vietnam: ruối.

Streblus comprises about 23 species and occurs in Africa and Madagascar, and from Nepal, India and Sri Lanka to Indo-China, southern China, Thailand, throughout the Malesian region towards the Solomon Islands, Australia, New Zealand and the Pacific Islands, east to Fiji, Samoa and the Cook Islands, and north to Hawaii. Only 5 species occur within Malesia.

The hard and very durable wood (mainly of S. elongatus) can usually only be obtained in small pieces and is mainly used for specialty items such as tool handles (especially the strong and elastic sapwood), carrying sticks, oars, spokes and cartwheels, but also for musical instruments, turnery, anchors, bows and fishing rods. Whenever large logs are available these are suitable for heavy construction, bridge building, wharves, boat building, parquet flooring, heavy-duty flooring, railway sleepers, power transmission poles and interior finish. It is regarded as one of the best local timbers for use in salt-water.

S. asper is a well-known medicinal plant. Its bark is traded as a medicine used to treat leprosy, piles, diarrhoea, dysentery and elephantiasis, and it shows anti-cancer and anti-malaria activities. In Thailand the bark is also used to manufacture paper; elsewhere in Indo-China also for rope and for rough clothing. In India the latex is put on sore heels and chapped hands, and on glandular swellings. Young leaves are fed to cattle in India and Indo-China. In Malaysia an extract of the leaves of S. asper is used to make milk coagulate with a texture similar to that of yoghurt. Old leaves of this species have been applied for polishing ivory. Ripe fruits of S. asper and S. ilicifolia can be eaten raw or boiled. In the Philippines S. asper is planted as an ornamental; in Indonesia it has been grown as cover crop in forest plantations.

Because of the very limited supplies and often small size of Streblus timber, it is used on a local scale only. It is, however, highly valued locally. In Peninsular Malaysia "tempinis" is regarded as a substitute for "chengal" (Neobalanocarpus heimii (King) P. Ashton).

Streblus yields a medium-weight to heavy hardwood with a density of 530-750 kg/m³ for S. asper and 920-1200 kg/m³ for S. elongatus. The following wood properties all refer to S. elongatus. Heartwood yellow to yellowish-red or brownish-red, darkening to dark chocolate-brown upon exposure, distinctly demarcated from the white to pale yellow-brown, up to 10 cm wide sapwood; grain interlocked, occasionally straight; texture fine to moderately fine and even; wood with distinct odour when freshly cut. Growth rings indistinct, occasionally visible, indicated by darker coloured bands with relatively few vessels and parenchyma; vessels moderately small to medium-sized, mostly solitary, sometimes in radial multiples of 2-4(-5) with occasional clusters, blocked by tyloses or filled with yellow-white deposits; parenchyma abundant, paratracheal aliform in the earlywood becoming confluent towards the end of the growth ring, in some samples apotracheal in marginal or seemingly marginal bands; rays very fine to moderately fine, not prominent on radial surface; ripple marks absent; radial latex canals rare and difficult to see.

Shrinkage upon air seasoning is low and the wood seasons without degrade. Boards of S. elongatus 13 mm and 38 mm thick take respectively about 2.5 and 3.5 months to air dry. The wood is very hard, very strong and extremely elastic. The wood is fairly difficult to work with hand and machine tools and severely blunts cutting edges. It is rather difficult to plane, but finishes and polishes well. Care must be taken in drilling, moulding and mortising to avoid chipping at the exit of tools. The wood is very durable when exposed to the weather or in contact with the ground. For S. elongatus the average service life of test stakes in a graveyard test in Malaysia was 11.3 years. Both sapwood and heartwood are resistant to preservative treatment. The wood is resistant to termite and to some extent to marine borer attack, the sapwood is non-susceptible to Lyctus but slightly susceptible to blue stain.

The gross energy value of the wood of S. asper is 17 830 kJ/kg. Adding the extract of leaves of S. asper to milk to curdle it does not change pH; the product is stable at pH 5.5-9.0, and up to 70 °C. It has been suggested that the milk coagulation factor may be a proteinase. The bark of S. asper contains glucosides with anti-cancer and cardiac activity.

See also the tables on microscopic wood anatomy and wood properties.

• Evergreen, monoecious or dioecious, armed or unarmed, shrubs or small to medium-sized trees up to 30 m tall; bole often irregular and fluted, branchless for up to 15 m, up to 60(-75) cm in diameter, without distinct buttresses; bark surface smooth, becoming finely and irregularly cracked or fissured, grey, inner bark yellowish or whitish, with or without milky latex; crown compact, dense.
• Leaves distichous or sometimes arranged spirally, simple, entire to toothed; stipules free or connate, lateral to completely amplexicaul. Inflorescence axillary, bisexual or unisexual, solitary or paired, cymose, racemose, spicate or capitate, sometimes the female flower solitary.
• Flowers unisexual. Male flowers 3-5-merous; tepals imbricate or valvate in bud; stamens bending outward at anthesis; pistillode present. Female flowers 4-merous; tepals free or almost free, variably unequal; ovary superior, free, 1-locular with a single ovule, stigmas 2.
• Fruit drupaceous or a dehiscent or indehiscent capsule; fruiting tepals enlarged or not, not to slightly fleshy.
• Seedling with hypogeal germination; cotyledons unequal, the larger not emergent, the smaller emergent; hypocotyl not elongated; first few leaves scale-like, lower leaves arranged spirally, subsequent ones distichous.

It seems that seedlings of S. asper develop into creeping shrubs that only later develop an upright branch that becomes the trunk. In Peninsular Malaysia S. elongatus flowers in January-August and November, but ripe fruits have rarely been collected. S. elongatus already flowers when about 1.8 m tall. The seeds of S. asper are dispersed by white ants which drag them into their nests, where they often germinate. The ripe fruits of S. elongatus are eaten by squirrels, monkeys and birds.

Streblus is a variable genus divided into 5 sections, and includes the genera Phyllochlamys, Sloetia and Taxotrophis. It is very closely related to Trophis, from which it mainly differs by the free versus connate tepals.

S. elongatus occurs scattered in lowland forest, and in open vegetation. S. asper is a characteristic element of monsoon forest; it also occurs in areas disturbed by man.

S. asper has been propagated by cuttings to establish a cover crop in forest plantations. Fruit setting of S. elongatus is poor as is its natural regeneration, but it coppices easily and may be found, therefore, coppiced in secondary vegetation. S. elongatus is considered shade-tolerant.

In Peninsular Malaysia and Singapore S. elongatus has been heavily depleted, because of its highly valued timber. S. asper has become rare in Java.

Although the wood of S. elongatus has outstanding qualities for specialty uses, supplies are very limited and dwindling; hence its use will probably decrease further.

70, 106, 151, 161, 163, 174, 205, 209, 217, 260, 261, 267, 340, 354, 387, 406, 436, 464, 526, 536, 672, 677, 678, 861, 883, 933, 973, 1038, 1169, 1221, 1239, 1242, 1262, 1268.