Dendrocalamus giganteus

Dendrocalamus giganteus Wallich ex Munro

Trans. Linn. Soc. 26: 150 (1868).
2n = 72 (hexaploid)

Origin and geographic distribution
The origin of D. giganteus is not known precisely, but could possibly be in southern Burma (Myanmar) (Tenasserim) and north-western Thailand. For map click: Map166.TIF. It is commonly planted in Sri Lanka, India, Bangladesh and southern China. In Peninsular Malaysia several old clumps of D. giganteus have been found growing scattered in the Penang Hills, but it is not known whether this population is natural or a naturalized escape from cultivation. D. giganteus has been introduced and planted in many botanical gardens, e.g. in Indonesia (around 1910), the Philippines (1990s), Indo-China, Madagascar (also outside botanical gardens).

The large culms of D. giganteus are used for many purposes, e.g. construction, scaffolding and rural housing, water pipes, buckets, boat masts, matting, woven wares and paper production. The thick-walled culms are especially good for the production of bamboo boards, which are ideal material for room decoration and other practical interior applications such as walls, ceilings, floors, doors, shelves, etc. The young shoots are edible (creamy and tender when cooked) but they are not widely consumed. They have a fair canning quality. D. giganteus can be planted to protect soil against erosion. As one of the largest bamboo species, it has a high ornamental value. In Thailand the large culm sheaths are used to make hats.

Production and international trade
Cultivated on a small scale, D. giganteus is locally important in South-East Asia, but no statistics are available. There are no reports of more extensive cultivation.

The fibre length of D. giganteus culms varies from 1.4-4.6 mm (averaging about 2.7 mm), diameter 26 µm, lumen diameter 19 µm, wall thickness 3.9 µm. These data indicate good paper-making quality. At a moisture content of 19% the density of the culm is about 900 kg/m3. Specific gravity is 0.71. The modulus of elasticity is about 14,044 N/mm2 (Indonesia); the modulus of rupture is 179 N/mm2 (Indonesia), 93 N/mm2 (with nodes, Brazil), 124 N/mm2 (without nodes, Brazil); the compression strength parallel to grain is 61.5 N/mm2 (Indonesia), 39 N/mm2 (with nodes, Brazil), 46 N/mm2 (without nodes, Brazil); the shear strength is about 4.5 N/mm2 (Brazil); the tensile strength is about 187 N/mm2 (Indonesia), 110 N/mm2 (with nodes, Brazil), 135 N/mm2 (without nodes, Brazil).

Densely tufted, sympodial, giant bamboo. Culm erect with arching tip, up to 30 m tall, 18-25 cm in diameter near the base, wall up to 2.5 cm thick, covered with a white waxy layer when young, becoming smooth, whitish to greyish-green; internodes 25-55 cm long, lowermost shortest; nodes not swollen, lower ones bearing aerial roots. Branches arising from midculm nodes, comprising one dominant branch and several smaller branches. Culm sheath caducous, 25-50 cm x 25-50 cm, widest at lower internodes, with dark brown hairs on the back; blade spreading, broadly triangular (on lower sheaths) to narrowly triangular, 13-38 cm x 9 cm, stiff, edges inflexed towards stiff acuminate apex, with scattered hairs adaxially, especially near the base; ligule 8-12 mm long, stiff, shortly fringed; auricles crisp, 1.5 cm x 3 mm, brown, not bristly. Young shoots purplish. Leaf blade oblique-oblong, 20-40 cm x 3-7 cm, glabrous, slightly rough, with distinct cross veins; ligule 2-3 mm long, irregularly toothed; auricles small and glabrous. Inflorescence borne on a leafless branch with few to many pseudospikelets crowded at each node, axes and internodes finely hairy; spikelet flattened, 13-17 mm x 4-5 mm, consisting of 4-6 florets, the uppermost one sometimes imperfect. Caryopsis oblongoid, 7-8 mm long, hairy above.

Growth and development
In Burma (Myanmar), offsets consisting of young shoots with small portions of attached rhizome produce small culms in the first year. Subsequent culms increase in size each consecutive year until, after 7 years, they have attained a girth of about 25 cm and a height of about 12 m. They are then harvested. However, culms attain full size ultimately at an age of 15-16 years.
Observations made in India reveal that D. giganteus culms grow very fast, averaging 20 cm per day during 3.5 months. At first, the growth of a young shoot is very slow, quickening gradually during a period of 4-6 weeks until the culm is about 4 m tall. Then maximum growth is attained and maintained for several weeks (e.g. on average, 32 cm per day), after which growth gradually decreases until it stops when full height is attained at the age of 3.5 months. Rapid growth seems to be induced by high relative humidity, irrespective of light and temperature, causing a high turgescence in the culm. Lower relative humidity increases the evaporation, which in turn decreases the turgescence and consequently the growth rate.
D. giganteus flowers gregariously and the flowering cycle is estimated to be 30-40 years; after flowering, the clump dies.
In Indonesia it has been observed that clumps survive when flowering culms are cut down. Culms grown from seed reached 6-8 m height and 10 cm diameter 3 years after sowing.

Other botanical information
In Burma (Myanmar) wild D. giganteus is found from Upper Chindwin through the Shan Hills to Moulmein. One-year-old culms are dark green with excessive white mealiness which easily comes off, and with loosely attached sheaths or brown remnants of sheaths present on the nodes. In the second year all sheaths have fallen, the ashy-grey remnants are still present, the culms are green but tinged yellowish near the nodes, especially in the lower half, and the white mealiness is 50% less than in the first year; more than half of the upper culm is covered with branches. In the third and fourth years, branching is even stronger and the mealiness is inconspicuously greyish-white and difficult to remove.

D. giganteus grows naturally in humid tropical highlands, up to 1200 m altitude. It can, however, be grown successfully in tropical lowlands on rich alluvial soils. In northern Thailand it is found in natural forests with teak.

Propagation and planting
D. giganteus is normally propagated by clump division. If available it can be propagated by seed. Propagation by culm and branch cuttings is possible, although difficult. Artificial induction of roots before taking the cuttings is possible and reasonably successful. In an 8 ha plantation in Burma (Myanmar), 40-50 clumps were grown per ha.

Competition between culms in a clump may cause 'abortive shoots', affecting about 50% of all new shoots. Young abortion-prone shoots usually grow within 20 cm from a culm, attaining about 13 cm height before dying. Such young shoots are suitable for vegetable use.

Diseases and pests
No serious diseases or pests are known to attack D. giganteus. The fungus Pycnoporus sanguinus and powder-post beetles may attack dry harvested culms. Submerging in mud for 1-4 weeks after cutting may give some protection against diseases and pests. Sometimes young bamboo shoots suffer from sap-sucking aphids (Oregma bambusae) which may cover young shoots completely and cause them to die. Spraying kerosene oil in soap emulsion can control the pest. Witches' broom may also occur in D. giganteus but without causing much damage.

The harvesting of culms from young clumps may start 7 years after planting. All 3-year-old culms from mature clumps (15-16 years old) can be cut annually.

A mature clump may yield 3-4 culms per year. With 50 clumps per ha, annual yield can attain up to 200 culms and 200 young shoots. The edible portion of young shoots is about 33%, or 550 g on average.

Handling after harvest
Traditionally, culms are submerged in running water or in mud to obtain some protection against powder-post beetles, and are air dried afterwards.

Genetic resources and breeding
Germplasm collections of D. giganteus are available in Bangladesh (Forest Research Institute, Chittagong), India (Arunachal Pradesh Centre bamboorium, Basar) and in Indonesia (Lampung, Sumatra). Representative collections from all provenances are needed. In India some work is being done on the selection of superior forms, but no breeding programmes are known.

Although the prospects for D. giganteus as a source of raw material for bamboo board, as an ornamental and as a vegetable (young shoots) are promising, it is necessary to investigate its requirements and appropriate cultivation techniques first and then to develop the required technology.

E.A. Widjaja

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