6505

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

Zanthoxylum L.

Sp. pl. 1: 270 (1753); Gen. pl., ed. 5: 130 (1754).

RUTACEAE

x = 16, 17, 18; Z. acanthopodium DC.: n = 32, Z. nitidum (Roxb.) DC., Z. rhetsa, Z. scandens Blume: n = 34

Ivy-rue, thorny yellow-wood (En). Malaysia: chenkring, hantu duri (Peninsular). Vietnam: s[er]n.

Zanthoxylum comprises about 200 species and has a pantropical distribution with a few representatives in temperate eastern Asia and North America. Most species occur in South America. The genus is found throughout South-East Asia and in northern Australia and the Pacific; there are 20 species within Malesia.

The wood of Zanthoxylum is used for house building (planking, rafters, scantlings), furniture and various small articles like jewelry boxes, kris handles and sheaths, axe handles, walking-sticks, inlay work, gun stocks, carving and novelties.
The fruits of Z. rhetsa are used as a spice and yield an essential oil that shows anthelmintic activity. In the Philippines its pounded bark mixed with oil has been used externally against stomach-ache, and a decoction of it is taken internally to cure pains in the chest. The chewed bark is applied to snake bites. The soft, fibrous material from the roots of Z. integrifoliolum has been used in the Philippines to caulk canoes.

Zanthoxylum wood is sold in local markets, and may be exported in mixed consignments of yellow hardwood. The fruits were formerly sold in local markets in Java and are traded in parts of Thailand.

Zanthoxylum yields a lightweight to medium-weight hardwood with a density of (290-)335-790 kg/m³ at 15% moisture content with samples of Z. rhetsa covering the whole range. Heartwood bright yellow to pale brown, not clearly differentiated from the pale brown sapwood; grain straight; texture fine to moderately fine and even; wood of several species lustrous. Growth rings usually distinct to the naked eye, boundaries indicated by layers of narrow marginal parenchyma, latewood slightly denser than earlywood, occasionally with a ring of solitary vessels in the earlywood; vessels very small to medium-sized, solitary and in radial multiples of 2-4, open, occasionally filled with chalky white deposits; parenchyma sparse to moderately abundant, paratracheal scanty to vasicentric, apotracheal banded in marginal or seemingly marginal bands; rays moderately fine to medium-sized, of the larger ones visible to the naked eye; ripple marks mostly absent, sometimes with a tendency to irregularly storied arrangement.
Shrinkage is high but the wood seasons well without degrade. The wood of Z. rhetsa is hard and tough, that of Z. myriacanthum is soft. It is easy to work by hand and machine and finishes to a shiny surface. The heartwood of Z. rhetsa is resistant to dry-wood termites and moderately resistant to fungi. The sapwood is usually non-susceptible to Lyctus. In a graveyard test in the Philippines the average service life of Z. rhetsa was 40 months, which is classified as moderately durable.
The average fibre length of Z. rhetsa is 1.15 mm. The most important chemical constituents of Malesian Zanthoxylum species are alkaloids and coumarins. The bark of several species contains alkaloids. The fruits of Z. rhetsa yield a volatile oil, about 50% of which consists of sabinene.
See also the tables on microscopic wood anatomy and wood properties.

Evergreen or deciduous, dioecious or rarely monoecious, scandent or erect shrubs or small to medium-sized trees up to 35 m tall; bole up to 60 cm in diameter, occasionally larger, without buttresses; bark surface often studded with spines or prickles, grey or brownish, inner bark fibrous, aromatic. Twigs armed. Leaves alternate, paripinnate or imparipinnate; leaflets 1-15, opposite to alternate, entire or glandular-dentate, with pellucid dots; stipules absent. Flowers in an axillary or terminal panicle, raceme or cyme or rarely solitary, unisexual or bisexual, small; perianth with 6-8 tepals or differentiated into 4-5 sepals and petals; stamens 4-6, rudimentary in female flower; disk flat to cushion-like; ovary superior, 1-5-carpellate, rudimentary in male flower, carpels free or fused at base, each with 2 ovules, styles fused to divergent, stigma capitate. Fruit composed of 1-5 free or basally fused follicles; exocarp glandular, red to black. Seed ovoid to globose, 1 per follicle, often hanging from a funiculus; testa black or reddish, glossy; endosperm present. Seedling with epigeal germination; cotyledons emergent; hypocotyl elongated.
Several species are myrmecophytes with hollow branches showing slit-like openings in which ants of the genera Camponotus and Crematogaster live. In Peninsular Malaysia Z. rhetsa is deciduous around March or April and flowers just after or just before the new leaves. In Java it flowers in December. The fragrant flowers are probably pollinated by insects. In Java ripe fruits of Z. rhetsa are available in February and March.
Zanthoxylum belongs to the subfamily Rutioideae and includes the genus Fagara. It is often misspelled as Xanthoxylum.

The timber-yielding Zanthoxylum species are found in primary and secondary forest and thickets, up to 2100 m altitude. Z. myriacanthum is locally common in secondary forest and thickets on hills and mountains. Z. rhetsa is generally found in rather dry, often monsoonal forest and thickets, up to 500 m altitude.

Z. rhetsa can be planted in the open provided it is above 400 m altitude. At lower altitudes it will benefit from some shade. It is not resistant to fire.

The narrow geographical distribution of some Zanthoxylum species may make them vulnerable to genetic erosion. The availability of Z. rhetsa in Bali is seriously reduced due to exploitation for the handicraft industry.

The pale-coloured wood of Zanthoxylum has potential for decorative articles. Since there is no experience with planting Zanthoxylum, silvicultural information should be obtained through experimentation.

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E. Boer (general part), M.S.M. Sosef (general part, selection of species), J. Ilic (wood anatomy)

Zanthoxylum celebicum
Zanthoxylum integrifoliolum
Zanthoxylum myriacanthum
Zanthoxylum pluviatile
Zanthoxylum rhetsa

Boer, E., Sosef, M.S.M. & Ilic, J., 1998. Zanthoxylum L.. 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:
Zanthoxylum celebicum
Zanthoxylum integrifoliolum
Zanthoxylum myriacanthum
Zanthoxylum pluviatile
Zanthoxylum rhetsa