Erythrina (PROSEA Timbers)

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Plant Resources of South-East Asia Introduction

List of species

Erythrina L.

Protologue: Sp. pl. 2: 706 (1753); Gen. pl., ed. 5: 316 (1754).

Family: Leguminosae

Chromosome number: x= 21; E. fusca, E. subumbrans: 2n= 42, E. variegata: 2n= 42, 44

Vernacular names

• Coral tree (En)
• Arbre au corail (Fr)
• Indonesia: dadap (general)
• Malaysia: dedap (general), dadap (Sabah), derdap (Peninsular)
• Philippines: dap-dap (Filipino)
• Burma (Myanmar): kathit
• Thailand: thong lang.

Origin and geographic distribution

Erythrina comprises about 110 species distributed pantropically. Tropical America is richest in species (about 70), followed by Africa (32), whereas Asia has 18 species. Some 6 to 8 species occur in Malesia, but many more are planted as ornamentals.

Uses

The usually lightweight wood of Erythrina is used by the local population for floats for outrigger canoes and fishing-nets, surf boards, dugout canoes, shields, spears, helmets, insulator boards, wooden shoes, carving, cheap artifacts, kitchen utensils and packing cases. It may be used for match splints. The pulp of some species (e.g. E. variegata) may be suitable for making paper.

Their conspicuous red flowers make many Erythrina species popular as ornamentals, and they are commonly planted in gardens and parks. They are also widely planted as shade trees, e.g. in cacao, coffee and tea plantations, and as living stakes to support black pepper (Piper nigrum L.), betel (Piper betle L.), yams (Dioscorea spp.) and vanilla (Vanilla planifolia H.C. Andrews). They are additionally used as green manure because they can fix atmospheric nitrogen in symbiosis with rhizobia. The more prickly forms are often planted as live fences. Several species are used in a variety of traditional medicine, e.g. for poulticing wounds, against toothache, cough and colds and in Java to temper or relieve fever of children ("dadap srep"). The leaves of some species (e.g. E. fusca and E. variegata) are eaten as a vegetable, and also used as fodder. The shiny red seeds are often used to decorate clubs or are made into necklaces, rosaries and good-luck charms. In Thailand the flowers of E. variegata have been used to dye clothes red.

Production and international trade

Within Malesia the wood of Erythrina is not harvested commercially and utilization is on a local scale only.

Properties

Erythrina yields a lightweight hardwood with a density of 240-380 kg/m³ at 15% moisture content. Heartwood pale straw or buff-coloured, not clearly differentiated from the white sapwood; grain straight, slightly interlocked or wavy; texture coarse and uneven; rays producing a faint check-pattern on radial surface. Growth rings usually indistinct; vessels moderately large to extremely large and characteristically few, solitary and in radial multiples of 2-3, also in small clusters, open; parenchyma abundant, paratracheal in confluent wide bands, conspicuous, also aliform; rays extremely broad; ripple marks present, but only from wood parenchyma and visible only with a hand lens, it is reported that all elements are storied in E. subumbrans.

Shrinkage upon seasoning is moderate to high. The wood is extremely soft, very weak but fairly tough. It is easy to work but difficult to finish because of the coarse texture. The wood is non-durable and susceptible to sap-stain fungi and dry-wood termites. The sapwood is susceptible to Lyctus. Wood of E. variegata absorbed about 215 kg/m³ of Wolman salt when soaked in hot water for 3 hours and then soaked in the Wolman salt solution for 2 hours.

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

Botany

• Mostly deciduous shrubs or small to medium-sized trees up to 27 m tall, occasionally small subshrubs or perennial herbs; bole and branches often armed with conical spines, bole often short and bifurcating but sometimes branchless for up to 21 m, sometimes crooked or fluted, up to 90(-170) cm in diameter, occasionally with buttresses up to 2 m high; bark surface cracked and flaky or fissured or furrowed, greenish-grey, grey to olive-brown, inner bark often yellowish; slash orange-brown or deep straw-coloured with orange tinge, sometimes with blackish streaks; crown often much branched.
• Leaves arranged spirally, pinnately 3-foliolate; leaflets entire, lateral ones often asymmetrical; stipules persistent or caducous, stipels usually fleshy and glandular.
• Flowers solitary, paired or fascicled in an axillary or terminal, racemose, inverted inflorescence, bisexual, often scarlet or red; calyx tubular-campanulate, bilabiate or spathe-like with a slit down to the base on the lower side, 5-lobed, sometimes inconspicuously so; corolla papilionaceous, often showy, keel and wings usually much smaller than standard; stamens 10, upper one free or partly connate with the staminal tube; ovary superior, stipitate, many-ovuled, style incurved.
• Fruit a stipitate pod, often constricted between the seeds, usually dehiscent, 1-14-seeded.
• Seed ovoid or ellipsoid, often red or orange, some with a black spot; cotyledons fleshy, endosperm absent.
• Seedling with epigeal or semi-hypogeal germination; cotyledons emergent or not emergent, fleshy; hypocotyl elongated; first 2 leaves opposite and simple, subsequent ones alternate and 3-foliolate.

Most species are deciduous during or after the dry season, and flower when leafless. The pendulous flowers are scentless, strong and elastic, and are typically pollinated by birds, particularly by passerines such as Chloropsis species and crows. They visit the flowers in the morning collecting the copious nectar. The seeds of E. fusca and E. variegata float and are distributed by sea currents.

The timber of E. vespertilio Benth. is traded as "grey corkwood" in Australia; the lightweight wood is used for model-making, insulating boards, light planking, surf boards, floats and shields. In India E. suberosa Roxb. is an important lightweight wood. E. sandwicensis O. Deg. is a favourite canoe wood in Polynesia.

Erythrina belongs to the tribe Phaseoleae, subtribe Erythrininae.

Ecology

Most Erythrina species occur in a monsoon climate and on sandy soils. E. fusca prefers wetter locations such as freshwater swamps, stream banks and badly drained soils, up to 2000 m altitude; it may develop into almost pure stands in such locations. E. insularis is found in lowland rain forest, in secondary and coastal shrub vegetation, and in savanna with Eucalyptus , up to 1200 m altitude. E. subumbrans occurs in open places or in secondary forest, often near streams, up to 1500 m altitude. E. stricta is usually found on or near beaches, whereas E. variegata is adapted to coastal forest, but it is frequently cultivated inland, up to 1200 m altitude.

Silviculture

Erythrina can be propagated by seed and by large stem cuttings. There are about 1450-5000 seeds of E. fusca per kg and germination is 80-95%. Seeds of E. variegata have about 30% germination in 6 days to 11 months but rapid germination in 8-10 days has also been recorded. Generally, large cuttings about 2-3 m long and 5-10 cm in diameter are used, these sprout easily in 2-4 weeks. They establish easily as the leafy twigs are out of reach of livestock. Cuttings of E. subumbrans up to 25 cm in diameter sprout readily. E. fusca has been recommended for reforestation in Java on very poor soils where Paraserianthes falcataria (L.) I.C. Nielsen fails to grow. When Erythrina is planted for shade, trees are pollarded once every 6 months to 2 years, and when used to support vines the branches are lopped every 6 weeks to 6 months. The foliage is used as a green manure or for fodder. Stakes of E. fusca in pepper plantations in Sumatra are frequently attacked by a stem borer (Bactocera sp.) and by a ring borer (family Lecanidae). At the end of the 19th Century E. subumbrans was severely attacked by a still unknown root disease in Java, which locally destroyed all trees. Around 1930 it was infested by a Fusarium disease in Java and South Sumatra. A top-boring caterpillar (Terastia meticulosalis) has been observed in Indonesia in Erythrina .

Genetic resources and breeding

E. fusca, E. subumbrans and E. variegata have large areas of distribution and are planted widely; they are not liable to genetic erosion. However, other species such as E. insularis occur only very locally, are rarely planted, and are much more vulnerable. Germplasm collections of Erythrina species including E. fusca and E. variegata are maintained in Hawaii and Costa Rica. There is a selection and breeding programme of E. fusca in the Centre for Tropical Agricultural Research and Trianing (CATIE) in Costa Rica, aiming at improving its shade tree characteristics.

Prospects

The prospects of Erythrina for timber production are not promising. The wood, which is often of poor quality, will probably remain a secondary product, although it has shown some potential for paper production. The emphasis will probably continue to be on its uses for auxiliary and ornamental purposes. Erythrina can be very valuable as a multi-purpose tree, given its uses as a green manure, forage and medicine.

Literature

7, 70, 91, 161, 163, 187, 209, 235, 238, 267, 304, 333, 343, 436, 464, 476, 519, 536, 637, 700, 780, 829, 831, 859, 933, 934, 975, 1163, 1221, 1242, 1264.