Parkia (PROSEA Timbers)
Introduction |
Parkia R. Br.
- Protologue: Denham & Clapp., Narr. Travels Africa, Bot. App.: 289 (1826).
- Family: Leguminosae
- Chromosome number: x= 12, 13; P. speciosa: 2n= 24, 26
Vernacular names
- Petai (trade name)
- Thailand: sato.
Origin and geographic distribution
Parkia is a pantropical genus with about 35 species, most of them being found in tropical America, especially in the Amazon basin. In Asia Parkia occurs from north-eastern India and Bangladesh east through Burma (Myanmar), Indo-China and Thailand to the whole of the Malesian region, with more isolated species in Micronesia and Fiji. About 5 species occur within Malesia. Peninsular Malaysia, Sumatra and Borneo are richest, each with 4 species. P. timoriana has the largest area of distribution, occurring from India to New Guinea.
Uses
The wood of Parkia is used locally for temporary light construction, carpentry, furniture and cabinet making, moulding, interior finish, cladding, concrete shuttering, boxes, crates, matches, clogs, disposable chopsticks, fish-net floats and paper. General utility purpose plywood has been manufactured from the wood. In Peninsular Malaysia P. singularis wood is a popular firewood.
This species is sometimes used as a shade tree, e.g. for coffee plantations and in nurseries. The seeds are commonly used as a vegetable; they have a garlic flavour. Young leaves and the receptacle of the inflorescence are occasionally eaten. The seeds are used in local medicine against hepatalgia, oedema, nephritis, colic, cholera, diabetes and as anthelmintic, and also applied externally to wounds and ulcers. Powdered bark of P. sumatrana has been reported to be used against leeches in Indo-China, and the bark of P. timoriana against scabies, boils and abscesses.
Production and international trade
Parkia timber generally does not reach the market because it is considered of poor quality and supplies are limited.
Properties
Parkia yields a usually lightweight, occasionally medium-weight hardwood with a density of 350-810 kg/m3at 15% moisture content. Heartwood white, yellow-white or pale yellowish-brown, in older trees with paler and darker streaks, not clearly differentiated from the rather wide paler coloured sapwood (25 cm wide sapwood once recorded for P. timoriana ), very occasionally darker coloured core present; grain straight or slightly interlocked; texture moderately coarse and uneven; wood with unpleasant garlic or bean-like odour when fresh. Growth rings indistinct or visible due to colour differences, narrow layers of marginal parenchyma only visible with a hand lens; vessels medium-sized to very large, mostly solitary, also in radial multiples of 2-3, sometimes more than 4, occasionally with red gum-like deposits; parenchyma abundant, paratracheal aliform and confluent, and apotracheal in marginal or seemingly marginal bands and diffuse, the latter type rare; rays very fine to medium-sized, visible to the naked eye; ripple marks absent, but rays irregularly storied; occasionally with pith flecks.
Shrinkage upon seasoning is low; degrade during seasoning is mainly due to insect attack and blue stain, whereas end-checks have been observed in P. speciosa . It takes respectively 3-4 months and 4.5-5 months to air dry boards 13 mm and 38 mm thick. The wood is soft to moderately hard in P. singularis and weak. The wood is relatively easy to work, saw and machine, both when green and when air-dry; it can be planed well and gives a smooth finish, but boring and turning give a rough finish. The production of rotary veneer is satisfactory, but the production of good-quality plywood is doubtful. The wood is non-durable with a service life of about one year for P. speciosa wood, but preservative treatment applying the standard open-tank method with creosote is very easy, and an absorption of 320 kg/m3has been obtained in P. speciosa . A dry salt retention of 12.3 kg/m3of copper-chrome-arsenic solution was obtained in treating P. speciosa wood by the vacuum-pressure method. The wood is not resistant to any kind of insect or wood-borer attack nor to wood-staining fungi. The sapwood is susceptible to Lyctus .
See also the tables on microscopic wood anatomy and wood properties.
Botany
- Deciduous, medium-sized to large trees up to 50 m tall; bole up to 100(-250) cm in diameter, buttresses small to large (up to 4 m high and spreading up to 2 m) or absent; bark surface smooth to rough, fissured or flaky, pale greyish to reddish-brown, inner bark fibrous, hard, usually pinkish or reddish to deep red-brown, sometimes streaked or mottled, with a strong smell of beans.
- Leaves alternate or opposite, bipinnate with up to 30(-42) pairs of pinnae; leaflets opposite, sessile; petiole and rachis usually with extrafloral nectaries; stipules small, caducous.
- Flowers in a long-stalked, pendulous, pyriform to clavate, dense head, sterile flowers at base of inflorescence, male ones in middle portion and bisexual ones at apex, 5-merous; calyx long-tubular or funnel-shaped with imbricate lobes; corolla longer than calyx; stamens 10, connate below, shortly exserted; ovary superior, short-stiped, style exserted.
- Fruit a leathery or woody, stalked, linear to strap-shaped or oblong pod, usually indehiscent, many-seeded, usually several pods together in a pendent infructescence with swollen receptacle.
- Seeds in 1 row, ellipsoid, with a pleurogram.
- Seedling with epigeal germination; cotyledons fleshy, peltate; epicotyl with a scale leaf and subsequently bipinnate leaves.
P. speciosa and P. timoriana show a synchronized annual cycle of flowering, fruiting and leaf fall; the trees are without leaves for 2-3 weeks each year. They start flowering when 10-15 m tall, but vegetatively propagated P. speciosa starts flowering and fruiting a few years after planting. The flowering heads are usually pollinated by bats, but are also visited by insects and birds. They produce a foetid odour and a copious nocturnal supply of nectar. Hornbills, monkeys, squirrels, deer, elephants and wild pigs feed on the fruits and probably disperse the seeds. In Java P. timoriana flowers in April-July and usually many fruits are found in June-August. A 24-year-old P. timoriana tree in the arboretum of the Forest Research Institute Malaysia, Kepong had attained only 13.8 m in height and 9.2 cm in diameter.
Parkia is classified in the tribe Parkieae of the subfamily Mimosoideae, together with Pentaclethra, which is confined to tropical Africa and America.
P. timoriana is often cited as P. javanica (Lamk) Merr., especially in Malaysian literature. Although the latter name is older and would therefore have priority, it has been superseded because the correct identity of the species concerned cannot be recovered. The status of P. intermedia Hassk. is uncertain, but it is probably a hybrid between P. speciosa and P. timoriana; it is found almost exclusively in Java. P. sherfeseei Merr. from the Philippines (Mindanao) is possibly conspecific with P. sumatrana.
Ecology
Parkia occurs scattered in lowland rain forest and sometimes also in tall secondary forest, on sandy, loamy and podzolic soils, also in waterlogged locations, in freshwater swamp forest and on river banks, up to 1000(-1400) m altitude. P. sumatrana and P. timoriana also occur in dry evergreen forest, often along streams.
Silviculture
Parkia can be propagated by seed and by vegetative means. Seeds of P. timoriana can be hand-picked from underneath mother trees from the hard, indehiscent pods that should be opened with a chopping knife. P. timoriana has 1000-1400 dry seeds/kg. Seedlings of P. speciosa are collected by farmers from the wild and planted in their home garden or fields. About 90% of the soft seeds of P. speciosa germinate in 3-15 days; the germination rate of the hard seeds of P. timoriana is about 55% in 8-103 days. Mechanical scarification is recommended for the latter. In a test in Thailand, 3-year-old seed had a germination rate of only 8.5% whereas nicked seed had a germination rate of 90.5% in only 4-8 days. A pretreatment with concentrated sulphuric acid for 15 minutes gave a germination of 95%. P. speciosa can be propagated by stem cuttings and budding, but P. timoriana cannot be propagated vegetatively. Seedlings of P. timoriana can be stumped with 10-20 cm shoot and 20-40 cm root length, and survival after planting is 100%. In Java growth during the first 5 years was fast, but then slowed down. For optimal growth ample space and light are necessary. Mixed plantations with Lagerstroemia speciosa (L.) Pers. and Artocarpus heterophyllus Lamk planted in alternating rows at 3 m × 1 m spacing were successful with a production of 65 m3/ha clear bole volume at the age of 15.5 years. The mean diameter of P. timoriana at this age is 15.6-20.4 cm and its height is 14.5-16.1 m. Some unidentified borers have been found tunnelling in the stem of living trees. In Malaysia it is recommended to treat timber of Parkia with anti-stain chemicals immediately after sawing. In a survey of almost 700 ha of primary forest in Peninsular Malaysia, an average of 0.22 trees/ha of P. singularis and P. speciosa with a diameter of over 40 cm was found, but usually these species are much less common.
Genetic resources and breeding
Within Malesia no seed or germplasm collections of Parkia are known to exist and no breeding programmes are being carried out. Most species have a fairly wide area of distribution and are also cultivated, suggesting that it is unlikely that they are threatened. P. versteeghii , however, seems to be rare.
Prospects
There is little scope for increased utilization of the timber of Parkia as it is non-durable and of poor quality. Only the quality and durability of the timber of P. singularis is slightly better, but its scattered occurrence makes exploitation difficult.
Literature
16, 70, 151, 162, 163, 198, 209, 235, 260, 267, 302, 304, 316, 341, 343, 348, 387, 405, 436, 448, 464, 488, 577, 632, 633, 677, 678, 679, 740, 741, 770, 780, 825, 829, 831, 832, 862, 882, 933, 934, 955, 972, 980, 987, 1015, 1039, 1053, 1163, 1198, 1218, 1221, 1226.