Gigantochloa scortechinii

Gigantochloa scortechinii Gamble

Ann. Roy. Bot. Gard. Calcutta 7: 62 (1896).
2n = unknown
Origin and geographic distribution
G. scortechinii is found in Indonesia (Sumatra), in central and northern Peninsular Malaysia and in southern Thailand. For map click: Map436.TIF. At present it has become naturalized and is found mostly in disturbed (logged-over) forest in the area. It is occasionally cultivated in and around villages and outside the area in botanical gardens.

G. scortechinii is the commonest and most used bamboo of Peninsular Malaysia. In villages or in the home its culms have numerous uses, e.g. in constructions and scaffolding, to make baskets and other utensils and a wide variety of handicraft materials. In small-scale enterprises, culms are used to produce chopsticks, toothpicks, skewers, blinds, joss sticks, large baskets, poultry cages and paper. The young shoots are rarely used as a vegetable because they are rather bitter.

Production and international trade
In Peninsular Malaysia the total area under G. scortechinii is estimated at 328,000 ha, but it often occurs mixed with other species. Economically it is one of the major species and it is mainly collected from natural or naturalized populations. Production and trade are mainly local but some export exists (e.g. In 1993, 17.25 t was exported to Taiwan, valuing M$ 5005). The paper mill price for a culm of 8-10 m length is about M$ 1.0-1.5.

Mature, 3-year-old green culms have an average basic density of 557 kg/m3. Their average fibre dimensions are: length 4.24 mm, diameter 17 µm, lumen diameter 3 µm, wall thickness 8 µm. The vascular bundle frequency is 1.83/mm2. At a moisture content of about 90%, for 3-year-old green culms the average modulus of elasticity is 4960 N/mm2, the modulus of rupture 59.43 N/mm2, the compression strength parallel to grain 28.79 N/mm2 and the shear strength 4.52 N/mm2. The culm contains mainly holocellulose 63.3% (alpha-cellulose 39.1%), and lignin 20%.

Densely tufted, sympodial bamboo. Culm erect, up to 20 m tall, up to 12(-20) cm in diameter, wall 5-10 mm thick, when young covered with a fine white waxy powder, bright green when old; internodes up to about 60 cm long, basal ones with light green stripes. Branches arising from the midculm node upward with primary and secondary ones. Culm sheath 15-25 cm long, light orange, covered with appressed black hairs, not easily deciduous; blade spreading to reflexed, lanceolate, 9-13 cm x 1-3 cm, leaf-like, light green, much narrower than top of sheath; ligule dentate or deeply incised, ending in bristles, up to 9 mm long; auricles forming a low dark green rim along the sheath apex, sometimes terminated by a few bristles. Young shoots light orange with light green blades covered with appressed dark hairs. Leaf blade 20-30 cm x 2-3 cm, softly hairy on the lower surface; sheath hairy; ligule 2 mm long, sometimes bearing bristles; auricles small, 1 mm long with a few bristles up to 6 mm long. Inflorescences borne on leafless branches, bearing at the nodes head-like clusters of pseudospikelets about 5 cm apart, each cluster with 2-5 large fertile pseudospikelets mixed with a few small sterile ones; spikelet ovoid to oblongoid, flattened, 18-20 mm x 5-6 mm, densely yellow-brown hairy or velvety, consisting of 2-3 empty glumes, then 3-5 perfect florets, terminating with an imperfect floret. Caryopsis ellipsoidal, glabrous, hairy at truncate top.

Growth and development
Under natural conditions, shoots of G. scortechinii emerge above the ground during the rainy season (August-mid October in Peninsular Malaysia) and develop to their full height in 4 months. A strong, positive correlation exists between the amount of previous year rainfall and the number of emerging shoots. Culm sheaths start to fall when 4-5 months old and branching starts when the culm has reached its full length. A culm becomes mature in 3 years. A good, healthy clump can produce 48-60 shoots annually, but only about 40% of these reach maturity. One-year-old seedlings attain about 1.10 m in length; in the next year they develop 2-4 new culms, after which clump formation develops rapidly.
G. scortechinii is a gregarious species, easily occupying large open areas. Plants raised from culm cuttings initially produce small shoots (3 the first year) which develop into small culms. In the following year shoots develop into larger culms, and after 6-7 years the shoots develop into full-sized culms.
Flowering of G. scortechinii is sporadic, i.e. only a portion of one clump flowers at a time; gregarious flowering has never been reported.

Other botanical information
Vegetatively, G. scortechinii looks rather similar to G. wrayi Gamble, but its orange-green young shoots are quite distinctive in the field.
Two varieties have been distinguished within G. scortechinii:
- var. scortechinii: culm sheath covered with blackish-brown hairs, auricles bristly; the most common variety;
- var. albovestita Holttum: culm sheath covered with white hairs, auricles glabrous; not so common.

In Peninsular Malaysia natural forests of G. scortechinii occur up to 1000 m altitude but they are best at altitudes between 400-800 m. Annual mean maximum temperature is about 32ºC, mean minimum temperature 22ºC. Annual rainfall is about 2500 mm, quite evenly distributed over the year. G. scortechinii will grow in any soil type but does best on sandy loams with good drainage and pH 5.0-6.5. It thrives well in ravines, gulleys and logged-over areas and is quite aggressive once it is exposed to sunlight.

Propagation and planting
G. scortechinii can be propagated by seed, rhizome and culm cuttings. Germination rate of seed is 70-75%. Rhizome cuttings (rhizome part, with roots and 60-100 cm basal part of a one-year-old culm) are planted out directly and are successful, but this method is not suitable for large-scale propagation. Culm cuttings are raised in a nursery for 4-6 months and transplanted when they have produced roots, preferably at the onset of the rainy season. It is recommended to prepare holes of 60 cm x 60 cm x 60 cm, to apply organic and inorganic fertilizers and to plant at distances of 3-6 m x 3-6 m. Due to the abundance and ubiquity of the species in the forest, in Peninsular Malaysia plantations of G. scortechinii do not exist.
Husbandry Weeding and watering in young plantations are necessary until the plants are well established. Annual fertilizer application of 20-30 kg N, 10-15 kg P, 10-15 kg K and 20-30 kg Si is recommended in Malaysia.

Diseases and pests
Leaves of G. scortechinii sometimes suffer from a leaf spot disease caused by Colletotrichum sp. and Pestalotia sp. Spraying with fungicides like thiram, benlate or captan controls the disease. Major pests are stem borer beetles (Estigmena chinensis, Conarthus jansoni) which attack young culms, and leaf rollers (Pyrausta coclesalis). Pest control is effective by removal of affected culms and thinning of congested clumps (sun kills the beetles).

Only mature culms of 3 years or older should be harvested, taking care not to harvest from the periphery of a clump and to leave the culms evenly spaced in the clump. In Peninsular Malaysia culms are harvested all the year round. Felling intensities up to 70% (70% of total number of culms of a clump) are possible without visible negative effect on regrowth.

A properly managed plantation may produce 3600-4000 culms/ha or 40-50 t (green weight) per year.

Handling after harvest
Culms of G. scortechinii are quite durable, but for preservation they are traditionally soaked in running water for 18-24 hours. For the poultry cages industry at Guar Chempedak (Peninsular Malaysia) culms are collected from natural forests and transported in 7-8 m lengths by lorry to the factory. There they are sawn into suitable lengths and split. The crosswalls at the nodes of the culms are then knocked away to allow greater flexibility. The strips are cut tangentially into two thinner parts which are used to weave the cages and their covers. Broader unsliced strips are used to reinforce the bottoms. For the joss stick production in Ulu Langat (Selangor) the culms are cut and smoothed into fine sticks. These are sun-dried for a few days before being coated with a mixture of fine sawdust, adhesive and perfume which make up the incense.

Genetic resources and breeding
For G. scortechinii no germplasm collections and no breeding programmes are known to exist.

Prospects The prospects for G. scortechinii are promising. Its culms are fully utilized and are in great demand. Investigations are in progress on natural stand management, fertilizer requirements and optimum felling intensity. It is recommended to start a representative germplasm collection.

Azmy Hj. Mohamed

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