Bambusa balcooa

Bambusa balcooa Roxb.

Fl. Ind. (Carey ed.) 2: 196 (1832).
2n = 72
Origin and geographic distribution
B. balcooa is only known from cultivation. For map click: Map263.TIF. It is thought to originate from northern India and Bangladesh where it is widely cultivated. Occasionally it is cultivated outside this region, e.g. in Java, Australia and in many botanic gardens.

The culms are used as building material for houses, bridges, temporary fishing floats, frames of rickshaw hoods, to prepare agricultural and fishing implements and to weave mats and baskets. In India the culms also serve as raw material for paper. Young shoots are used as a vegetable. In Bangladesh, leaves are used as emergency fodder.

Production and international trade
B. balcooa is only cultivated on a small scale, in home gardens or village groves. No statistics are available. Whole culms or pieces are sold in local markets in Bangladesh and transported from rural to urban areas and from the northern to the southern part of the country. In Bangladesh the average price per culm was about US$ 2 in 1994.

Fibres in the culm of B. balcooa have the following average dimensions: length 2-21 mm, diameter 24 µm, lumen diameter 17 µm, wall thickness 3.2 µm. The moisture content of 2-5-year-old green culms ranges from 97% to 146%. Specific gravity of 2-5-year-old culms ranges from 0.46-0.69 (green culms) and 0.73-0.82 (oven-dried culms). Mature culms (3 year or older) suffer very little or no collapse on air drying. After being dried to about 12% moisture content, the average shrinkage of mature green culms ranges 7-24% for wall thickness and 2-11% for diameter. For 3-5 year-old green and air-dried culms the following mechanical properties have been reported: modulus of elasticity 5800-11,600 N/mm2 (green), 7100-13,700 N/mm2 (air dried); modulus of rupture 42.8-89.0 N/mm2 (green), 52.9-99.0 N/mm2 (air dried); compression strength parallel to grain 24.2-42.7 N/mm2 (green), 29.8-65.2 N/mm2 (air dried).

A densely tufted, sympodial bamboo. Culm erect with pendulous tip, (5-)17.5(-30) m tall, 2.5-10 cm in diameter near the base, wall more than 2 cm thick, dirty silvery-brown pubescent; internodes 20-45 cm long, 6th-8th internodes generally longest, sometimes slightly sulcate; nodes swollen, with a supranodal ridge, lower nodes bearing aerial roots, above and below the nodes with a circular band of fine whitish-brown hairs. Branches arising from all nodes, those from the lower nodes bearing no leaves, small and sometimes recurved and thornlike. Culm sheath 15-35 cm x 15-40 cm, in lower nodes much shorter and wider than in upper ones, deciduous, green when young, covered with blackish-brown hairs on the back, margin ciliate along one edge, along the other edge only at the top; blade triangular, erect, 6-8 cm x 5-7 cm, adaxial surface dark brown pubescent, margin ciliate; ligule membranous, 5-8 mm long, denticulate; auricles absent or very small, ciliate. Young shoot blackish-green, covered with blackish hairs. Leaf blade oblong-lanceolate, 15-30 cm x 2.5-5 cm, glabrous, margin ciliate. Inflorescence compound, up to 1 m long, bearing spicate branches with pseudospikelet groups; spikelet ovoid, lanceolate or flattened, 6-12 mm x 4-6 mm, with 4-6 fertile and 0-2 sterile florets. Caryopsis not known.

Growth and development
The shoots of B. balcooa emerge above the ground during the rainy season and reach full culm length within 2-3 months. The lateral branches develop simultaneously with the elongation of the culm. A culm becomes mature in 3-4 years. From an experiment on culm production and clump expansion in Bangladesh, in which planted offsets were left undisturbed during 10 years, it appeared that the average clump diameter increased from 9.5 cm one year after planting to 80 cm after 5 years and 130 cm after 10 years. The average production of full-grown culms per year increased from one in the first year to 3 after 5 years and decreased to 2 in the remaining years, probably due to increased competition. The average culm length increased almost linearly from 2.5 m in the first year to about 23 m in the 7th year and remained constant at about 22 m in the following years. The average culm diameter increased linearly from 1.5 cm in the first year to a constant maximum of about 8 cm from the 7th year onwards. It seems advisable to start harvesting mature culms about 6 years after planting; selective cutting may encourage new culms to develop.
B. balcooa flowers rarely but gregariously; the flowering cycle is estimated at 35-45 years.

Other botanical information
B. balcooa can be confused with Dendrocalamus calostachyus (Kurz) Kurz from upper Burma (Myanmar) which has similar culms and culm sheaths. In Burma (Myanmar) it is used as construction material for small buildings and for domestic purposes.

B. balcooa is grown at altitudes up to 600 m, in a tropical monsoon climate with an annual rainfall of 2500-3000 mm and a dry season of up to 6 months. It grows in any type of soil but prefers heavy textured soils with good drainage and pH of about 5.5.

Propagation and planting
B. balcooa can be propagated vegetatively by rhizome, culm and branch cuttings. Root formation in culm cuttings is effectively promoted by treatment with growth regulators like naphthalene acetic acid (NAA), but auxin and kinetin are most effective in two-nodal branch cuttings that are 1 year old. The propagules are raised in a nursery and after they have produced roots and developed rhizomes they are planted out in the field during the rainy season in pits filled with a mixture of cow dung and soil, at recommended distances of 4-5 m x 4-5 m.

Young plants need watering when rainfall is not sufficient. Before the start of the monsoon rains, clumps are generally mulched and culm bases are covered with soil. Congested clumps should be drastically cleared and annual thinnings are necessary.

Diseases and pests
In Bangladesh a serious disease of B. balcooa is bamboo blight, attacking young bamboos during or soon after the elongation growth and resulting in dieback. Sarocladium oryzae (= Acremonium strictum) is the main fungus associated with blight symptoms, but the causal agent is not yet known. Insects spread the disease within a culm but also to other culms. Improvement of cultural practices (burning of infested parts, mulching and covering clumps with soil before the rainy season, not overharvesting culms) promotes the growth of more healthy and vigorous culms in clumps, and such culms are less susceptible to blight. Drenching the soil of affected clumps with fungicide (e.g. fytolan 0.4% or dithane M45 0.4% before the rainy season also promotes survival of new culms.

Mature culms (yellowish) are generally harvested during the dry season by cutting them close to the ground level. Young shoots are usually harvested during the rainy season.

In Bangladesh a good clump produces 3-4 mature culms per year. With 400 clumps/ha (distance 5 m x 5 m), annual production can amount to 1200-1600 culms/ha.

Handling after harvest
After cutting, the culms are debranched and traditionally are immersed for 2 months in stagnant water to protect them against powder-post beetles. After drying, whole culms or culm segments are sold in local markets. The natural durability of B. balcooa is poor. Various preservative treatments are known, but no specific information is available for B. balcooa. Green culms can be treated according to the boucherie process method in which culms are immersed in a preservative solution.

Genetic resources and breeding
Small germplasm collections of B. balcooa are available in India (Arunachal Pradesh Centre bambusetum, Basar and in Van Vigyan Kendra, Chessa) and Bangladesh (Bambusetum of Bangladesh Forest Research Institute, Chittagong). Although always propagated vegetatively, variation occurs in culm diameter, culm height, number of young shoots and internode length. Larger germplasm collections have to be established before selection programmes can be carried out. Variability is best visible in clumps 4.5 years old.

In Bangladesh, B. balcooa is one of the most important village bamboos used for construction. It is worthwhile investigating if this bamboo can be cultivated equally successfully in South-East Asia. Many aspects, however, still require more research, particularly shoot production, food value of shoots, selection of disease-resistant and high-yielding cultivars, cultivation methods and mechanical properties of the culms.

M.K. Alam

For additional information about author(s) see Contributors or Editors.