Thyrsostachys siamensis

Thyrsostachys siamensis Gamble

Ann. Roy. Bot. Gard. Calcutta 7: 59 (1896).
2n = unknown

Origin and geographic distribution
T. siamensis is native in Burma (Myanmar) and Thailand, where it occurs widely and often abundantly in pure stands. In many other tropical regions, especially in South-East Asia, it has been introduced and is cultivated widely as an ornamental and as wind-break. For map click: Map85.TIF.

In its native area, T. siamensis is one of the most useful bamboos. The culms serve for house construction and general household uses, as well as raw material for cottage industries. In Thailand the culms are also widely used to make baskets, chopsticks, umbrella and broom handles, handicrafts, fishing rods and they serve as raw material for paperpulp and as fuel. Young shoots are consumed as a vegetable and considered as among the best bamboo shoots. Because of its elegant habit (compact clumps of outcurving slender culms bearing many small leaves on slender branches) T. siamensis is a popular ornamental plant. It is also planted in rows as wind-break.

Production and international trade
In Thailand, T. siamensis is commercially one of the most important bamboos and is extensively exploited from natural stands. Annual production fluctuates between 30-40 million culms. In central Thailand the occurrence of T. siamensis as pure stands is estimated at 450,000 ha. In northern Thailand 100,000 ha occurs in mixed forest. In Lampang (Thailand), about 500,000 culms of T. siamensis are sold annually. Here, 6 chopstick and cocktail stick factories use 5000 t bamboo as raw material and 16 ceramic factories use 100,000 m3 dry bamboo culm per year as fuel. In Kanchanaburi (Thailand) a paper mill uses culms of T. siamensis exclusively, producing about 10 t paper per day or 3500 t/year, consuming 5 million culms or about 9000 t (air dry). In 1985, 1986 and 1987 about 8350 t, 4250 t and 4500 t culms of T. siamensis, worth about US$ 55,000, 50,000 and 66,000 respectively, were exported to Europe, especially to Germany, United Kingdom and Italy.
Harvesting of T. siamensis shoots from natural stands and selling to processing factories provides subsistence income to local people. In Phu Khieo district (Chaiyaphum Province, north-eastern Thailand) it is estimated that over 500 t of shoots are harvested annually. Steamed shoots are available in most local markets all year round. Shoots are also exported (e.g. to Japan).

The fibres in the culms of T. siamensis are on average 3.14 mm long and 17.1 µm wide. The chemical composition of the culms is approximately: holocellulose 68%, lignin 24%, pentosans 17%, ash 2%; the solubility in hot water is about 5.7%, in alcohol-benzene 6.1%. Per 100 g edible portion, young shoots of T. siamensis contain approximately: water 89.5 g, protein 3.8 g, fat 0.3 g, carbohydrates 4.5 g, fibre 0,7 g, ash 1.0 g, Ca 12.8 mg, Fe 40.2 mg, P 0.2 mg, vitamin B1 0.01 mg, vitamin B2 0.09 mg and traces of vitamins A and C. The energy value is about 140 kJ/100 g. The 1000-seed weight is about 500 g.

Densely tufted, sympodial bamboo. Culm erect or with arching tips, 8-14 m tall, 2-7.5 cm in diameter, wall very thick, solid in lower part, smooth, greyish-green, usually covered with persistent old culm sheaths; internodes 15-30 cm long, bearing a white ring below the nodes; nodes not swollen. Branches arising from midculm nodes upwards, with many branches at each node of which the primary one dominant. Culm sheath 20-25 cm long, 10-20 cm wide near the base, narrowing up to 2.5 cm wide at the apex, persistent, pale to purplish-green turning stramineous and thin with age, covered with scattered, pale appressed hairs; blade narrowly lanceolate, 6-15 cm x 5-12 mm, erect, pubescent adaxially; ligule very short, shortly laciniate; auricles absent or very small. Young shoots pale to purplish-green. Leaf blade narrow, linear, 7-14 cm x 5-8 mm, pale green, usually glabrous; sheath striate, white hairy along the margins; ligule very short, entire, ciliate; auricles absent or very short. Inflorescences borne terminally on leafy or leafless branches, consisting of a main branch and many thin branchlets bearing bracteate clusters of few pseudospikelets; spikelet about 17 mm long, comprising 1 empty glume, usually 2 perfect florets and a rachilla extension bearing a rudimentary floret. Caryopsis cylindrical, about 5 mm x 2.5 mm, surmounted by a yellowish, glabrous, soft, long beak.

Growth and development
Seeds of T. siamensis germinate immediately after ripening and germination percentage is 90-95%. Stored at 25-30ºC, at moisture content of 10% or 6%, seed remained viable for 3 months; after 6 months, germination percentage had dropped to 60% and 86%, after 9 months to 33% and 82%, after 15 months to 1.5% and 71% and after 21 months to 0% and 1% respectively. With storage at 2-4ºC and at -5ºC, with moisture content between 6-10%, seed remains viable for at least 27 months.
In natural populations T. siamensis produces young shoots during the rainy season (in Thailand mainly between May and July). In Thailand 'on' years with many new shoots, alternate with 'off' years with many fewer new shoots. Generally, more shoots are produced if rain is abundant. A clump is considered as good if it has 30 culms on average, but clumps may have up to 100 culms. In Thailand, a 3-year-old plantation of T. siamensis raised from seeds, produced on average 38 culms per clump with average diameter 1.4-2.3 cm, of which 28 culms per clump were harvestable on average.
Flowering of T. siamensis is sporadic and gregarious. In Thailand sporadic flowering is common, and usually occurs between November and February. Mature seed can be collected from February to April. After flowering, culms usually die. Gregarious flowering is rare and the flowering cycle is not known. In season climates, T. siamensis is deciduous in the dry season.

Other botanical information
Some doubts exist regarding the correct botanical naming of T. siamensis. It may be that the first validly published name for the species was Bambusa regia Thomson ex Munro (1868), but here the views of Gamble and Holttum are followed who consider B. regia as a dubious name.

The natural habitat of T. siamensis is a dry or semi-evergreen forest on poor soils. However it will grow on a wide range of soils, provided they are not waterlogged. Its growth is not much hampered by partial shading. In Thailand it grows in mixed deciduous and teak forest in the north and north-east and pure stands often occur in hill forest in the central part, at altitudes 300-400 m, with annual rainfall of 800-1000 mm.

Propagation and planting
T. siamensis can be propagated by seed, rhizome cuttings and by tissue culture. Due to its common sporadic flowering, seed is always available. Propagation by rhizome cuttings (offsets) is most generally practised. The cuttings are taken from 1-year-old culms with rhizome part, roots and up to 1 m long culm part, planted in a nursery for 2-3 months and transplanted to the field in the rainy season. In general, 10 rhizome cuttings can be taken from a 5-6-year-old clump, retaining 4-5 one-year-old culms in the clump. Optimum planting distance for T. siamensis is 4 m x 4 m. Propagation by tissue culture is still experimental. Promising results were obtained by induction of multiple shoots from single seedlings.

Husbandry Weed control is necessary during early establishment of plantations. Regular earthing up of clumps, annual application of 100 kg/ha NPK (15-15-15) fertilizer, or 600-900 kg/ha animal manure are recommended. It is very important to protect natural stands and plantations against fire and grazing.

Diseases and pests
No serious diseases or pests have been reported for T. siamensis. Powder-post beetles and fungi can cause damage to harvested culms, although 3-year-old culms are considered relatively resistant.

Preferably, 3-4-year-old culms are cut in a 3-year-felling cycle. One-year-old culms are left to produce new shoots and 2-year-old culms serve to support the clump. In Thailand, in the dry season one person can harvest about 1700 culms per month from natural stands, giving an income of 4500 Baht (225 US$) per month. In the rainy season about 1500 kg young shoots per month can be harvested, giving an income of 1500-6000 Baht.

From natural stands, the average annual production in Thailand is estimated at 1500 culms/ha. In 'on' years, however, annual production may rise to 2500-3000 culms/ha (9-15 t/ha). No data are available on shoot production.
A plantation of T. siamensis starts to produce harvestable culms and shoots 3 years after planting. Profits can be made from the 4th-5th year onward by selling culms and young shoots. In the third year 1.5-2.5 t/ha of air-dried culms are produced.

Handling after harvest
Culms are traditionally submerged for 10-20 days in running water to reduce starch and sugar contents, and subsequently cleaned, polished and dried. For furniture making, culms are fire cured, which requires much skill to avoid damage. Chemical preservation methods include boiling for 15-20 minutes at 95ºC in a 0.2% sodium carbonate or 0.1% calcium hydroxide solution, or at 50-70ºC in a 0.3% copper sulphate solution. For home consumption, young shoots are boiled or parched. For commercial purposes, young shoots are steamed and peeled within 24 hours after harvesting and stored in vacuum containers or canned, either sliced or whole.

Genetic resources and breeding
No germplasm collections or breeding programmes are known to exist for T. siamensis.

The future of T. siamensis is bright: the demand for culms and young shoots is increasing. Promotion of T. siamensis cultivation is urgently needed, because of overexploitation of natural stands. Research should focus on proper cultivation methods and management of natural stands. Germplasm collection is urgently needed to conserve natural variability.

S. Duriyaprapan and P.C.M. Jansen

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