Ixora (PROSEA Timbers)

Plant Resources of South-East Asia Introduction

List of species

Ixora L.

Protologue: Sp. pl. 1: 110 (1753); Gen. pl., ed. 5: 48 (1754).

Family: Rubiaceae

Chromosome number: x= 11; for most species: 2n= 22

Vernacular names

• Indonesia: areng-arengan (Javanese), ki soka (Sundanese)
• Malaysia: jarum-jarum, pechah periuk, todong periok (Peninsular)
• Burma (Myanmar): pan, ponna
• Cambodia: chann tanea, tè prey
• Thailand: kheme (general).

Origin and geographic distribution

Ixora comprises about 400 species and is distributed throughout the tropics. The Indo-Malesian region is richest in species. In Malesia about 160 species occur; the highest number of species is found in Borneo, about 65, most of them endemic. Only a few species reach timber size.

Uses

The wood of Ixora is occasionally used, often for implements and comparatively small objects such as walking sticks, sometimes also for beams in house building.

Some Ixora species are well-known as an ornamental (e.g. I. chinensis Lamk, I. coccinea L., I. javanica (Blume) DC.), commonly planted in gardens, parks and roadsides. Several species are used in traditional medicine, e.g. as an astringent and to treat dysentery and tuberculosis. Some species (e.g. I. coccinea ) have shown anti-tumour and anti-mutagenic activity. The fruits of I. philippinensis Merr. are edible.

Production and international trade

Utilization of the wood of Ixora is limited and on a local scale only.

Properties

Ixora yields a heavy hardwood with a density of 940-1010 kg/m³at 15% moisture content. Heartwood pale brown with a pinkish tinge, not clearly differentiated from the sapwood; grain straight; texture very fine and even. Growth rings visible to the naked eye, defined by a layer of parenchyma; vessels moderately small, almost exclusively solitary with very occasional radial pairs, open; parenchyma moderately abundant, apotracheal diffuse and diffuse-in-aggregates, or in narrow or marginal bands, very occasionally scanty paratracheal; rays extremely fine or very fine; ripple marks absent.

The wood is very strong and durable. As the vessels are very small, the sapwood is probably non-susceptible to Lyctus .

See also the table on microscopic wood anatomy.

Botany

Generally evergreen (in Malesia) shrubs or small to sometimes medium-sized trees up to 25 m tall; bark surface smooth, lenticellate, fissured or scaly, greyish-brown; twigs terete, often with series of rather close, leafless nodes especially at branching points. Leaves opposite or sometimes in whorls of 3, simple, entire; stipules connate at base, distinctly cuspidate or with a long, stiff, needle-like extension at the tip. Flowers in a terminal corymb or corymbose panicle, 4-merous, often 3 together; calyx often divided to the base; corolla with a cylindrical tube, lobes contorted in bud, often white but sometimes pink, yellow or red; stamens inserted at corolla throat, with short filaments, anthers sagittate and reflexed out of the open flower; disk annular; ovary inferior, 2(-3)-locular with 1 ovule per cell, style slightly exserted from the corolla tube, with 2-lobed stigma. Fruit a globose to 2-lobed drupe, ripening red to black, 1-2-seeded. Seedling with epigeal germination; cotyledons leafy, green.

Flowering is seasonal but cultivated varieties bloom throughout the year. The flowers are mainly pollinated by moths and butterflies probing for the nectar at the corolla base, but honey-suckers may also visit the flowers, particularly the reddish ones. The fruits are probably dispersed by fruit-eating birds.

Pavetta closely resembles Ixora , but can be distinguished by its long-exserted style with coherent stigmas.

Ecology

Ixora species are usually confined to lowland and lower montane forest up to 1700 m altitude. Some species are also found in swampy locations in the vicinity of rivers or occasionally in rice fields (e.g. I. grandifolia ).

Silviculture Ixora may be propagated by seed, although ornamental species are usually propagated by cuttings. Both seed and sown fruits of I. lobbii Loudon had about 25% germination in 1-3 months.

Genetic resources and breeding

Ixora trees are not much sought after for their wood, since they are small in size. Therefore, logging for timber does not seem to affect the size of its population, except when an area is clear cut.

Prospects

Ixora timber is seldom used, mainly because of its small dimensions. Its utilization is unlikely to increase.

Literature

70, 137, 163, 209, 267, 436, 790, 829, 831, 861, 1164, 1221.