Peronema (PROSEA)

Plant Resources of South-East Asia
Introduction

Protologue: Malayan Misc. 2(7): 46 (1822).

Family: Verbenaceae

Chromosome number: x= unknown

Trade groups

Sungkai: lightweight hardwood, a single species, Peronema canescens Jack, Malayan Misc. 2(7): 46 (1822), synonym: Peronema heterophyllum Miq. (1860).

Vernacular names

Sungkai

false elder, kurus (En)
Indonesia: jati sabrang (general), jati londo (Java), kurus (Kalimantan)
Malaysia: sukai, cherek (Peninsular)
Thailand: sangkae (Surat Thani), khoeilai (Chumphon, Ranong), sakae (Malay, Narathiwat).

Origin and geographic distribution

Peronema is a monotypic genus and is native in Peninsular Malaysia, Sumatra, the Riau Archipelago, West Java and Kalimantan (especially the centre). It is cultivated in Indonesia, Malaysia and Thailand. It may have been introduced into Java from Sumatra but it is now fully naturalized.

Uses

The lightweight, non-durable timber is used for pillars in houses, interior finishes, and especially for roof trusses on account of its lightness and strength. It has been used to make carts, and bridges for light traffic. The attractive linear figure makes it suitable for furniture and cabinets as well as for decorative veneer. In Kalimantan and the Riau Archipelago small-scale furniture factories are often supplied with sungkai, which is used as raw material for external frames.

The tree is often planted in hedges. In traditional medicine the bitter juice of the leaves and a decoction of the bark are used against fever. Boiled leaves are used in a poultice against ringworm, and in a mouth-wash against toothache.

Production and international trade

The wood of sungkai is mostly used locally. It can be obtained in fairly large quantities and is regularly available. The current price in Java is US$ 90/m³ and sungkai is classified as a luxurious timber. In Indonesia, export to Japan is becoming important.

Properties

Sungkai is a light to medium-weight and moderately hard wood, with some resemblance to teak. The heartwood is cream-coloured to light yellow or light brown, and not clearly demarcated from the sapwood. The density is (360-)520-730 kg/m³ at 15% moisture content. The wood surface is moderately glossy, and the radial surface shows a figure of distinct and straight lines. The grain of the wood is straight, but sometimes slightly wavy, texture moderately fine to moderately coarse and often rather uneven.

At 15% moisture content the modulus of rupture is 56-67 N/mm², modulus of elasticity 8000-8400 N/mm², compression parallel to grain 31-34 N/mm², shear 4-7 N/mm², cleavage c. 61 N/mm radial and 64 N/mm tangential, Janka side hardness 2530 N and Janka end hardness 2960 N. See also the table on wood properties.

Sungkai dries fairly rapidly without serious defects, but cracking may occur. Boards of 25 mm thick take about 2 months to air dry.

The working qualitites are rated as moderately easy, but the presence of silica in the wood may blunt saws. Planing, shaping and turning give moderate results. Boring and sanding give good results. Good veneer can be made at a peeling angle of 9230', and the veneer can be glued with urea-formaldehyde to produce good-quality plywood.

Sungkai is rated as moderately durable; it has an average service life in contact with the ground of about 3 years. It is moderately resistant to dry-wood termites, is resistant to powder-post beetle attack, but is readily attacked by pinhole borers. The wood is not discoloured by sapwood-staining fungi. It is easy to treat with preservatives.

The wood contains 49% cellulose, 16.5% pentosan, 1.6% ash and 0.4% silica. The solubility is 4.0% in alcohol-benzene, 1.1% in cold water, 5.3% in hot water, and 11.3% in a 1% NaOH solution. The energy value is 20 150 kJ/kg.

Description

An evergreen or deciduous shrub or small to medium-sized tree up to 20(-30) m tall; bole straight or slightly flexuous, branchless for up to 9(-15) m, up to 70 cm in diameter, usually with small buttresses; root system superficial, with a short taproot; bark surface dirty grey or light buff, smooth to fissured and fibrous or scaly; crown ovoid; twigs 4-angled, densely short-hairy.
Leaves opposite, imparipinnate, purplish tinged when young; petiole and rachis winged, together (16-)30-90 cm long; leaflets in 3-11 opposite or subopposite pairs, sessile or shortly stalked, lanceolate, up to 35 cm × 7.5 cm, base cuneate and slightly unequal, acute to acuminate at the top, the upper leaflets increasing in size, margin entire (serrate in saplings), densely pubescent and pale whitish beneath, lateral veins 20-30 pairs, parallel, prominent below; stipules absent.
Inflorescence paniculate, terminal or in the axils of the upper leaves, large and widely branched, erect, 25-60 cm long, densely shortly grey tomentose.
Flowers bisexual, small, subsessile, 5-merous; calyx densely pubescent outside, about 2.5 mm long but slightly enlarged in fruit, the lobes slightly shorter than the tube; corolla bilabiate, with a short bell-shaped tube, white or greenish-white, appressed pubescent outside, upper lip bifid, lower lip 3-fid, longer than the upper, with a large median lobe of 2.5 mm long; stamens 2, inserted at the base of the widening part of the corolla tube, far exserted, filaments glabrous; ovary 4-celled, the cells 1-ovuled, densely pubescent, style far exserted, with a subulate top.
Fruit drupaceous, dry, globose, small, 3-3.5 mm in diameter, densely pubescent, splitting into 4 parts, with many pendulous seeds.
Seedling with epigeal germination; cotyledons equal, petiolate, ovate with an emarginate apex, entire or coarsely 2-4-dentate; first leaves pinnately lobed, subsequent ones imparipinnate.

Wood anatomy

Macroscopic characters

Heartwood cream-coloured to yellowish or light brown, often with a light red tinge, not clearly distinct from the sapwood.
Grain straight, sometimes slightly wavy.
Texture moderately fine and even or moderately coarse and uneven.
Growth rings conspicuous on all surfaces; wood ring porous, pore rings producing dark lines on longitudinal surfaces, vessels visible with a lens, in pore rings medium-sized to moderately small; parenchyma and rays only visible with a lens; ripple marks and intercellular canals absent.

Microscopic characters

Growth ring boundaries marked by difference in vessel frequency and vessel size.
Vessels 5-8/mm², in pore rings in radial or oblique rows of 2-3 and 180-260 μm in tangential diameter, in latewood mostly solitary but occasionally in radial pairs, 100-170 μm in tangential diameter; perforations simple; intervessel pits alternate, minute; vessel-ray pits similar to intervessel pits, but occasionally simple.
Fibres 900-1600 μm long, with an average diameter of 19 μm, non-septate, moderately thick-walled (3.5-4μm), with simple to minutely bordered pits.
Parenchyma moderately abundant, paratracheal, aliform, mainly vasicentric, forming complete or incomplete borders to the vessels, and tending to form discontinuous confluent layers; terminal parenchyma present at the borders of the growth rings.
Rays 4-7(-12)/mm, usually 4-10-seriate, 200-800 μm high, 40-60μm and 1-3 cells wide, heterogeneous (Kribs type heterogeneous II and III).
Crystals absent, silica bodies often present in ray cells.

Growth and development

Sungkai trees need much light for optimal growth. At first, growth is reasonably rapid in full light, but slows down later, even on fertile soils. Seedlings grow fast when fully exposed, but when shaded, even lightly, the stems become very slender and brittle. Mean annual growth increments in trial plots in a logged-over area in East Kalimantan were 120 cm in height and 0.8 cm in diameter for saplings, and 114 cm in height and 1.5 cm in diameter for pole-sized trees. In East Java 7-year-old trees had an average height of 9.5 m and an average diameter of 10.3 cm.

First flowering occurs when trees are about 5 m high, in Java at an age of approximately 5 years. Flowering season in Java is in June/July, in South and East Kalimantan in January/February. Fruiting occurs about 2 months after flowering. The seeds are dispersed by wind and water.

On dry sites the tree may be deciduous but in wet sites it may be evergreen.

Other botanical information

The genus Peronema is assigned to the subfamily Caryopteridoideae on the basis of its cymose inflorescence and its drupaceous, 4-parted fruit. Its closest relatives probably belong to the genus Glossocarya , which differs in having 4 stamens and a narrow fruit with basally winged seeds. Sungkai resembles elder (Sambucus spp.), hence the name false elder. However, the leaves of sungkai are not foetid when crushed, its flowers are not fragrant and the large panicles with small dry fruits and winged petioles are quite distinctive.

Ecology

Sungkai is common in secondary forest, forest clearings, river banks, along roads and railways, and in open country. It does not occur in primary forest and it grows best in moist to wet sites, even if they are flooded seasonally; it does not withstand very dry conditions well. Sungkai occurs naturally from sea-level up to 600(-900) m altitude.

Luxuriant natural regeneration occurs in open, disturbed places such as logged-over areas, making sungkai one of the species that benefit from disturbance of the forest.

Propagation and planting

Seeds germinate soon under full light, but collected seeds do not germinate well. The weight of 1000 seeds is 3.5-4 g.

The common method of propagation is by stem cuttings taken from straight trees. Experiments in Indonesia showed that cuttings 1.5-2 cm in diameter and 20-25 cm long give the best rooting results. The application of growth hormones to promote rooting may result in 100% rooted cuttings of juvenile material within 8 days. Trees from stem cuttings will finally develop a superficial root system similar to that of trees grown from seed. Cuttings placed directly in the soil may develop rot, especially at the base if thick. The planting medium commonly used in nurseries consists of topsoil and green manure (7 : 2), sometimes with some additional sand.

After 4-6 months the young plants may be transplanted. Planting distance in Indonesia is usually 3 m × 1 m, but spacings of 3 m × 2 m and 4 m × 2 m are also used. In plantations the canopy closes after about 8 years.

Silviculture and management

Sungkai is unsuitable for planting in mixtures with other species, but it may be used as first cover for the planting of dipterocarp species. Self-pruning does not occur sufficiently. Artificial pruning is necessary; wounds caused by artificial pruning heal fast and seldom cause rot.

Diseases and pests

Seedlings under shade are often attacked by leaf rust. Shoot-boring insects that tend to attack the tops may deform trees, but the damage is not serious.

Harvesting

In Palembang it has been found that long-term storage of the wood in running water is beneficial, and petrifies the wood in 6 years. Sunkai is usually clear felled when the trees have reached an average diameter of 20 cm or more. Fresh logs should not be debarked and both ends should be treated to prevent ambrosia beetle attack. Logs protected this way can remain in the forest for 30 days.

Yield

Mean annual volume increment was about 10 m³/ha in a 15-year-old stand, planted at a spacing of 3 m × 1 m in Gadungan (Indonesia).

Genetic resources

In Indonesia sungkai supplies from natural forests are becoming depleted, but as natural regeneration is often abundant in disturbed areas, there seems to be no direct danger of threat to P. canescens. There are plantations of several hundreds of ha in Central and East Java and in logged-over concession areas of East Kalimantan.

Prospects

The planting of sungkai offers bright prospects, and more plantations are already planned in Indonesia. Sungkai is able to grow on very poor soils, and even stems with a small diameter can be used. More reliable information is needed, especially on the silviculture and management of plantations.

Literature

Backer, C.A. & Bakhuizen van den Brink, R.C., 1965. Flora of Java. Vol. 2. Noordhoff, Groningen. p. 612.
Desch, H.E., 1954. Manual of Malayan timbers. Vol. 2. Malayan Forest Records No 15. Malaya Publishing House Ltd., Singapore. pp. 625-626.
Japing, H.W. & Oey Djoen Seng, 1936. Trial plantations of non-teak wood species in East Java. With survey of the literature about these species. Short Communications of the Forest Research Institute No 55. Part I-IV. Archipel Drukkerij, Buitenzorg. pp. 178-191. [Dutch, with introduction and conclusions in English.]
Marsudi, 1992. Peningkatan produktivitas lahan hutan di Gombong Selatan dengan mengembangkan tanaman sungkai [Productivity improvement of forest soils in Gombong Selatan by growing sungkai trees]. Duta Rimba 18(141-142): 45-46.
Martawijaya, A. & Kartasujana, I., 1981. The potential use of Indonesian timbers. Indonesian Agricultural Research and Development Journal 3(4): 116.
Martawijaya, A., Kartasujana, I., Kadir, K. & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 141-145.
Masano, A.H. & Omon, R.M., 1980. Pertumbuhan permudaan alam jenis jabon dan sungkai pada areal bekas tebangan HPH PT. ITCI, PT. BFI dan PT. Telaga Mas, Kalimantan Timur [Natural regeneration growth of jabon and sungkai in logged-over areas in the concessions PT. ITCI, PT. BFI and PT. Telaga Mas, East Kalimantan]. Laporan No 341. Lembaga Penelitian Hutan, Bogor. 33 pp.
Masano, A.H. & Siagian, Y.T., 1989. Pengaruh dosis rootone F terhadap pertumbuhan stek batang sungkai (Peronema canescens Jack) [Effect of rootone F on the growth and development of stem cuttings of sungkai (Peronema canescens Jack)]. Buletin Penelitian Hutan No 509: 27-36.
Moldenke, H.N., 1980. Notes on the genus Peronema. Phytologia 45: 339-349.
Priasukmana, S. & Yusliansyah, 1988. Kajian ekonomi industri mebel kecil [The economic study of small furniture industry]. Wanatrop 3(2): 38-54.

Other selected sources

84, 99, 153, 261, 318, 578, 779.

Authors

N.R. de Graaf (general part),
J.W. Hildebrand (general part),
R.P. van der Zwan (properties),
J.M. Fundter (wood anatomy)