Dendrocalamus asper (Schultes f.) Backer ex Heyne
Nutt. pl. Ned.-Ind., ed. 2, vol. 1: 301 (1927).
Gramineae
2n = unknown
Origin and geographic distribution
The origin of D. asper is not certain, but is thought to be somewhere in South-East Asia. It is planted throughout tropical Asia, and in many parts of Malaysia (e.g. Sabah and Sarawak) and Indonesia (e.g. Sumatra, East Java, South Sulawesi, Seram, western Irian Jaya) it has become naturalized. For map click: Map85.TIF. It has also been introduced in other tropical countries, such as Madagascar and Sri Lanka. It has been planted in botanical, experimental or private gardens in the New World and Australia, even in warm temperate areas.
Uses
The culms of D. asper have thick walls and are very strong and durable. They are used as building material for houses and bridges. The upper internodes of the culm, which are longer than the lowermost ones, are used as containers for water or to collect juice being tapped from palm inflorescences. In Sarawak, the internodes of this and other bamboo species are also used as ready-made cooking pots in the field. The internode is opened at one end (or the node) and filled with vegetables, meat or rice, and water, and is then covered and placed on a fire. The young and tender shoots ('rebung') are consumed as a vegetable. In Thailand D. asper is known locally as sweet bamboo, because the shoot is not bitter. In the areas where culms of D. asper are highly valued for building material, the shoots are rarely collected as a vegetable. On the other hand, where the culm is not much used, this bamboo is planted solely for its shoots. The shoots of D. asper are the best among those of other tropical Asiatic bamboos.
Production and international trade
In tropical Asia bamboos are of great economic importance in rural areas, and D. asper is one of the most important. It is planted on a small scale or harvested and collected from naturalized populations. It has recently been planted commercially in Thailand for its young shoots. The culm is used for local consumption only, and there are no statistics on its economics and production. The shoot has just come onto international markets. In Thailand the planted area of D. asper is estimated to be 6000 ha. In Prachinburi Province (Thailand) shoot production in 1984 was 37,975 t from 4465 ha. The price was 2-8 Baht/kg, depending on the time of the year.
Properties
The approximate fibre dimensions of the culm of D. asper are: length 3.78 mm, diameter 19 µm, lumen width 7 µm, wall thickness 6 µm. The moisture content of green culms averages 55% (76% at bottom, 36% at top), of air-dry culms 15% (15-17% lower half, 13-14% top). The specific gravity is about 0.7. At drying, radial shrinkage is about 5-7%, tangential shrinkage 3.5-5%. For green (moisture content 55%) and air-dry (moisture content 15%) culms, the modulus of rupture is 81.6 N/mm2 and 103.4 N/mm2, the compression strength parallel to grain 22.8 N/mm2 and 31.4 N/mm2 and the shear strength 6.96 N/mm2 and 7.25 N/mm2, respectively. The chemical composition of the culm is approximately: holocellulose 53%, pentosans 19%, lignin 25%, ash 3%; the solubility in cold water is 4.5%, in hot water 6%, in alcohol-benzene 1%, in 1% NaOH 22%.
The edible portion of young shoots is about 34%, weighing on average 5.4 kg before peeling and 1.8 kg after peeling. Their canning quality is good.
Description
Densely tufted, sympodial bamboo. Culm erect with pendulous tip, 20-30 m tall, diameter 8-20 cm near the base, wall 11-36 mm thick, sometimes almost solid at base, when young covered with fine, velvety, golden-brown appressed hairs, later glabrous; internodes from 10-20 cm (lowermost) to 30-50 cm or more (upper ones) long, white waxy below the nodes; nodes swollen, lowest nodes bearing many aerial roots. Branches arising from the midculm nodes upwards, few at each node with the primary one dominant. Culm sheath 20-40 cm x 20-25 cm, smallest in lower part, covered with dark brown to pale brown hairs; blade lanceolate, 30 cm x 3 cm, at first erect, later deflexed; ligule about 10 cm long, lacerate; auricles prominent, bearing slender bristles along the edges. Young shoots covered with dark brown to black hairs, blades small and deflexed. Leaf blade 30 cm x 2.5 cm, base shortly attenuate, glabrous above, hairy or glabrescent below; sheath glabrous or with scattered appressed pale hairs; ligule very short; auricles absent. Inflorescence borne on a leafless branch of a leafy or leafless culm, with groups of pseudospikelets at the nodes; spikelet slightly laterally flattened, 6-9 mm x 5 mm, pubescent, comprising 4-5 florets often with a sterile apical floret. Caryopsis not known.
Growth and development
As in any large tropical bamboo the shoots of D. asper emerge above the soil during the rainy season and develop to their full height in less than a year. However, in exceptionally brief rainy seasons the growth ceases and will continue when the next rain starts. The lateral branches develop when the culm reaches its full height. A culm becomes mature in 3-4 years. A good healthy clump can produce several shoots annually. Initially, a young plant raised from a lateral branch cutting will produce small shoots which will develop into small culms. The culms produced later are larger than those produced from previous years. Full-size culms appear five or six years after planting. A mature clump may attain a diameter of 3 m or more and contains about 60 culms.
Other botanical information
D. asper can be confused with Gigantochloa levis (Blanco) Merrill because of its large culms. G. levis is believed to be native in the Philippines; it is found planted or naturalized in many parts of Borneo (Sabah and Sarawak) and in the eastern part of Indonesia. Culms of G. levis have thinner walls than culms of D. asper, the internodes are not covered by golden-brown hairs and the nodes are not prominently swollen.
A primitive cultivar of D. asper in Indonesia, characterized by blackish culms, has almost become extinct.
Ecology
In tropical Asia D. asper is planted or naturalized from low altitudes up to 1500 m altitude. It thrives best, however, at 400-500 m above sea-level, in areas with average annual rainfall of about 2400 mm. D. asper will grow in any type of soil, but it grows better on heavy soils with good drainage. In Thailand, according to local farmers, D. asper will grow well on sandy and rather acidic soils.
Propagation and planting
D. asper can be propagated by rhizome, culm and branch cuttings and by tissue culture. The propagules are raised in the nursery and after they have produced roots they are planted out in the field before or during the first half of the rainy season. They are planted in holes containing a mixture of manure and chemical fertilizer, at distances 5-10 m x 5-10 m. Tissue culture is still experimental, but promising results have been obtained in Thailand, where already 1 million plantlets are distributed yearly.
Husbandry
Young plants require regular watering and weeding during the growing period because they cannot compete for nutrients, light and moisture. It is recommended to fertilize mature clumps yearly, one year with 100-300 kg/ha of 15-15-15 NPK and the next year with 50-60 kg/clump of manure, to improve soil texture and fertility. Mulching is necessary to increase the production of young shoots.
Diseases and pests
In Indonesia, D. asper is sometimes attacked by a witches' broom (Epichloe bambusae), which, however, causes little visible damage. The powder-post beetles Dinoderus minutus and D. brevis cause considerable damage to harvested culms.
Harvesting
Young shoots are usually harvested during the rainy season (in Java from November to May, in Thailand from May to June). Culms are preferably harvested in the dry season. It is recommended to harvest mature culms, 5-7 years old, and always to leave some mature culms in the clump.
Yield
No data are available on culm yield. In Thailand, a properly managed plantation may produce 10-11 t young shoots per ha per year. A 5-7-year-old plantation with 100 clumps/ha can produce 1000 young shoots per year. According to local farmers in Indonesia, a good clump bearing about 10 culms produces 60 young shoots annually. A well-managed plantation with 400 clumps/ha may produce 20 t young shoots per ha per year.
Handling after harvest
Traditionally, harvested culms are soaked in water or mud to decrease starch and sugar contents. For better preservation, several treatments with chemical solutions are possible. In Indonesia a modified boucherie treatment, using chemicals based on borax and boron, is most successful. The young shoots of D. asper are sold for local consumption, usually fresh or boiled, but in markets in Sulawesi and the Moluccas dried shoots also are offered for sale. In Thailand, shoots are also steamed.
Genetic resources and breeding
In Lampung (Indonesia) a germplasm collection of D. asper has been established. There are no breeding programmes. D. asper is available in many botanical gardens in the tropics. It is not clear whether the populations of D. asper in Indonesia and Malaysia are genuinely wild populations. Due to its vegetative reproduction, the plants are everywhere very similar.
Prospects
The prospects for D. asper are very promising. Young shoots can be produced in large quantities from plantations to meet increasing demand. The culms are promising for the development of furniture and chopstick industries. Many aspects, however, still require further investigation, e.g. propagation, management and the fertilizer requirements for young shoots and for culm production.
S. Dransfield and E.A. Widjaja
For additional information about author(s) see Contributors or Editors.