6529

17: Fibre plants

Ceiba pentandra (L.) Gaertn.

Fruct. sem. pl. 2: 244 (1791).

BOMBACACEAE

2n = 72—88

Bombax pentandrum L. (1753), Eriodendron anfractuosum DC. (1824).

Kapok, (white) silk-cotton tree (En). Arbre kapok, kapokier, fromager (Fr). Indonesia: kapuk (general), kau-kau (Bugis). Malaysia: kabukabu, kekabu, kapok. Philippines: kapok (Bisaya, Sulu, Tagalog), buboi, balios (Tagalog). Cambodia: koo, kor. Laos: ngiuz baanz, kok niou, ngiou. Thailand: nun (general), ngiu noi, ngiu sai (northern). Vietnam: (c[aa]y) g[of]n.

Kapok originated in the American tropics. From there it spread to Africa, where it occurs in the wild along the west coast from Senegal to Angola. It was taken from Africa to Asia to be cultivated; here the cultivated form was developed. Kapok is depicted in reliefs in Java dating from before 1000 AD. It is now cultivated all over the tropics, but mainly in South-East Asia, especially in Indonesia and Thailand.

The fruits of Ceiba pentandra are the source of the kapok fibre used for stuffing (e.g. mattresses, pillows, upholstery, protective clothing), and for thermal and acoustic insulation. Lifebelts and life-jackets used to be made from kapok fibre, but were only effective in the days of sail and steam, when there was no danger of oil in the water. During the Second World War many people drowned because their kapok life-jackets had lost buoyancy; nowadays synthetic material is used. In Java the placenta is crushed to produce a secondary quality kapok fibre for cheaper mattresses and for use as an absorbent for oil-contaminated sea water. Placental material is also used for culturing fungi. The shells of the fruits serve as a substitute for pulp material for paper making in Java.
The shells are rich in potash and the ash can be used as fertilizer. They are also used to make baking soda and soap. Dry shells are used as fuel. The seeds contain an oil which is used for soap manufacture, as a lubricant and as lamp oil. The oil has also been used for culinary purposes, but this is not advisable for health reasons. The residual presscake is used as animal feed. In Indonesia and Malaysia the seeds are eaten, but only in small quantities as they upset the digestion.
Young leaves are eaten as a leaf vegetable in the Philippines, young flowers and fruits are eaten in Thailand, and very young pods are eaten in Java. The leaves are used as fodder for cattle and as a soil improver. The wood is used for paper making and for making canoes, carvings, doors, furniture, boxes and toys. The flowers are a good source of nectar for honeybees. In various locations kapok is planted for reforestation, watershed conservation and for supplying fuelwood and fence posts.
In traditional medicine throughout South-East Asia preparations of the leaves are taken against fever, cough, hoarseness and venereal diseases. The bark is considered diuretic and astringent and also serves to treat fever, asthma, gonorrhoea and diarrhoea. The root is considered a diuretic and febrifuge as well. In India root decoctions are used against chronic dysentery and ascites. The Mayan and Aztec people in Central and South America regarded the kapok tree as sacred: its size and stature led them to regard it as a link between the earth and the universe. The kapok tree still has sacred significance for local peoples in many parts of the world.

The kapok tree was an important commercial fibre crop before the Second World War. Indonesia was the most important producer, exporting about 20 000 t per year of very good quality kapok. After the Second World War Indonesian production decreased and Thailand became the main supplier of the world market. Thailand also surpassed Indonesia in the quality of the kapok produced. However, Indonesian kapok production increased again from less than 30 000 t per year in the 1960s to about 80 000 t in 1996—2000, whereas the annual kapok production in Thailand remained stable at about 40 000—45 000 t. Most of the kapok produced was for home consumption. Indonesia, for instance, exported only about 800 t per year, mainly to India, Singapore and the United States.
In 1996—2000 Indonesia produced 206 000 t kapok seed in shell, 20 000 t kapok oil and 109 000 t kapok seed cake per year. The annual production in Thailand was 112 000 t kapok seed in shell, 13 000 t kapok oil and 59 000 t kapok seed cake. There is little international trade in these by-products. In 1996—2000 Indonesia exported on average 250 t kapok oil per year, with the importing countries including Japan and Singapore.

Kapok is the floss derived from the inner fruit wall in which the seeds lie loose when ripe. The total dry matter of ripe fruits, by weight, is composed of 21% fibre, 48% shell, 25% seed and 6% placenta. The fibre cells are (8—)19—22(—35) mm long and (10—)19—20(—30) µm wide, smooth, transparent, cylindrical, with a wide lumen and thin walls. They appear as structureless bent tubes. At one end they taper to a point, whereas the other end has a slightly bulbous base with annulate or reticulate markings. Kapok fibre contains about 43% 'ALFA'-cellulose, 32% hemicelluloses, 13—15% lignin and 1% ash. It is resilient, elastic, light (8 times lighter than cotton), water-repellent and buoyant (5 times more than cork). In an uncompressed state, it can support 20—30 times its own weight in water. This is because when the fibre is immersed in water, the lumen only partly fills with water and contains many air bubbles. Kapok fibre has a low thermal conductivity and very good sound-absorbing properties. A disadvantage of kapok fibre is its high inflammability, but techniques have been developed to make it non-flammable. In its natural form, kapok cannot be spun, because of the smoothness of the outer surface. However, specific techniques have been developed to make spinning of kapok possible. The fibre is long-lasting and is not attacked by fungi and pests.
The seeds yield 11—28% oil. The oil, which greatly resembles cotton-seed oil, contains cyclopropenoid fatty acids such as malvalic acid (7—8%) and sterculic acid (3—4%), which cause abnormal physiological reactions in animals. For this reason the consumption of kapok seeds or seed oil should be discouraged, unless the cyclopropenoid acids have been chemically removed. Per 100 g the press cake contains approximately: moisture 14 g, protein 26 g, fat 8 g, carbohydrates 23 g, fibre 23 g and ash 6 g. The K content of the shell is about 3%, and that of the ash 20—23%.
Bark extracts of Ceiba pentandra have shown anti-inflammatory activity in vivo and in vitro. Workers exposed to kapok dust for long periods may develop chronic bronchitis, and people involved in processing of kapok fibres are advised to wear protective masks.

Floss obtained from the red silk-cotton tree (Bombax ceiba L., synonyms: Bombax malabaricum DC., Salmalia malabarica (DC.) Schott & Endl.) has many of the qualities of Ceiba pentandra, but is less resilient, has a more brown or yellow colour, and can support only 10—15 times its own weight in water. Bombax anceps Pierre is also used for stuffing, for instance in Thailand. Other fibres used as a lower quality substitute for kapok include those of Asclepias curassavica L., Asclepias incarnata L., Asclepias syriaca L., Calotropis gigantea (L.) Aiton f., Calotropis procera (Aiton) Aiton f., Ceiba aesculifolia (Kunth) Britten & E.G. Baker, Ceiba trischistandra (A. Gray) Bakh., Chorisia insignis Kunth, Chorisia speciosa St. Hil., Cochlospermum religiosum (L.) Alston and Typha spp. Kapok has been adulterated with low-grade cotton (Gossypium spp.) and cotton waste. For industrial purposes kapok has largely been replaced by synthetic products, for instance for the production of life-jackets.

A deciduous tree, 18—70 m tall, in cultivation usually 18—30 m tall. Roots spreading quite horizontally, 10 m or longer, in the upper 40—80 cm of the soil. Trunk with or without buttresses, forked or unforked, spiny or spineless. Branches whorled, dimorphic, whorls usually of 3 branches, horizontally or ascending. Leaves alternate, digitately compound; petiole 7—25 cm long; leaflets 5—11, oblong-lanceolate, 5—16 cm x 2—4 cm, glabrous. Flowers 2—15 together in axillary fascicles, 5-merous, hanging, actinomorphic, bisexual; pedicel 2.5—5 cm long; calyx campanulate, 1—1.5 cm long, 5-lobed, glabrous outside; petals oblong-obovate, 2.5—4 cm long, united at base, usually dirty white with foetid milky smell, glabrous inside and densely silky outside; stamens united at base in a staminal column, dividing into 5(—6) branches of 3—5 cm length, anthers coiled or reniform; style 2.5—3.5 cm long, constricted at base, obscurely 5-lobed at top. Fruit an ellipsoidal, leathery, pendulous capsule, 7.5—30 cm x 3—7.5 cm, turning brown when ripe, dehiscing with 5 valves ('shells') or indehiscent, many-seeded. Seed obovoid, 4 -6 mm in diameter, dark brown, embedded in copious, white, pale yellow or grey silky wool (floss). Seedling with epigeal germination.

Seeds germinate within 3 days after sowing. In 6 months the young plants reach a height of 1 m. Two forms are recognized among the cultivated types: the 'pagoda' form with whorls of 3 horizontal branches spaced evenly along the main stem, and the 'lanang' form with irregularly spaced branches.
In Java flowers are initiated before leaf-fall, and flowering occurs on leafless branches at the beginning of the dry season, which starts between March and May. The flowers do not all appear at once, but over a period of 4—6 weeks. Flower buds open 15—20 minutes after sunset. The next morning and during the following day, the petals show the first signs of wilting. The same holds for the filaments and style. At the end of the day, wilting is complete and the flower, with stamens and style, drops off. Self-pollination is predominant in kapok plantations. During the night, the wind moving the flowers causes pollen to be shed on the stigmata of the same flower or neighbouring flowers. Where present, nectarivorous bats are pollinators. Insect pollination occurs in the morning. In Java beehives are placed in plantations to encourage pollination. Natural pollination results in about 8% of fruits ripening. The undeveloped fruits are shed after flowering, during the first and late fruit falls at 4 and 16 days after flowering, respectively. The fruits reach their full size 30 days after flowering. The kapok is formed between the 30th and 70th days and the fruit is ripe on about the 80th day. The size of the fruit and the amount of kapok fibre is proportional to the number of seeds set.
The trees start to bear after 3—4 years, but do not reach full bearing until 7—10 years old. Trees may continue bearing for 60 years or more.

Ceiba Miller contains about 10 species, mostly occurring in tropical America. Ceiba pentandra is distributed pantropically and is highly variable. Sometimes three varieties are distinguished:
— var. caribaea (DC.) Bakh. Occurring wild in the forests of the American tropics and in West Africa; a gigantic tree, up to 70 m tall, with unforked, buttressed and spiny trunk, and horizontal branches; leaf-shedding irregular, leaves narrow; flowering starting in the 11th year and irregular, flowers rose or cream-coloured; fruits rather short and broad, dehiscent; fibre grey to white; 2n = 80, 88.
— var. guineensis (Schum. & Thonn.) H.G. Baker. Occurring wild in savanna woodlands of West Africa; up to 18 m tall; trunk spineless without buttresses, often forked; branches strongly ascending; leaves broad; flowering annually; fruits elongated and narrow at both ends, dehiscent; fibre grey; 2n = 72.
— var. pentandra (syn. var. indica (DC.) Bakh.). The cultivated kapok of West Africa and Asia; up to 30 m tall; trunk unbranched, usually spineless, buttresses small or absent; branches horizontal or ascending; leaves intermediate in width; flowering annually, starting in the 4th year after sowing, after leaf-shedding; fruits short or long, narrowed at both ends or banana-shaped, usually indehiscent; fibre usually white; 2n = 72—84. Because this variety is the cultivated kapok it is more appropriate to classify it as cultivar group Kapok.
Alternatively, var. caribaea and var. guineensis are grouped into one variety (var. caribaea) as 'forest type' and 'savanna type', respectively.

Kapok thrives best at elevations below 500 m. Night temperatures below 17°C retard germination of the pollen grains. This limits the area in which good crops can be grown to latitudes within about 20°N and 20°S. Kapok requires abundant rainfall during the vegetative period and a drier period for flowering and fruiting. Rainfall should be about 1500 mm per year. The dry period should not contain more than 4 months with less than 100 mm rain per month, and in this period a well-distributed total rainfall of 150—300 mm is required. In drier areas, some of the water demand may be met by groundwater. In the Mekong Delta (Vietnam), where rainfall is inadequate, kapok is grown successfully on river banks. For best results it should be planted on good, deep, permeable soils (in Indonesia volcanic loams) without waterlogging. The tree is easily damaged by strong winds. In Indonesia, flat areas alongside roads and rivers are selected for planting the tree, as these locations have sufficient sunlight and proper drainage. In Java and Sulawesi kapok is also planted on mountain slopes.

Kapok is propagated by seed or cuttings. Seeds are sown in nursery rows 25—30 cm apart. If the soil is poor, manure should be applied 10 days before sowing. When the young plants are 12—15 cm tall, they can be exposed to full sunlight. Plants not receiving much sunshine grow tall and thin. Young plants are transplanted to the field when 8—10 months old, after the crown has been removed to leave about 1 m of stem. Another method is to sow directly on land which has been properly cleared for planting. Three seeds are sown per hole, and about 2—3 months later, the seedlings are thinned to one per hole. Kapok is easily propagated from cuttings, 5—8 cm in diameter and 1.2—1.8 m long, of 2—3-year-old wood. Cuttings should be taken from orthotropic branches. Trees raised from seeds root deeper than those raised from cuttings, but develop slower, yield less and do not breed true. Therefore in Indonesia it is now recommended that seedlings be grafted with material from high-yielding clones and trees. Grafting is done at the beginning of the rainy season and the grafted seedlings are planted out in the field when the buds have grown into shoots 1 m long. In commercial plantations in Java kapok is planted 8—12 m apart.
In South-East Asia kapok trees are planted around villages, on farmers' plots or on commercial plantations. It is also often planted along roads and on field boundaries. In Java kapok is very seldom planted as a sole crop. It is intercropped with various crops, including cassava (Manihot esculenta Crantz), groundnut (Arachis hypogaea L.) and turmeric (Curcuma longa L.). In Cambodia intercropping with annual crops such as maize, cotton and beans is practised during the first 2—3 years after planting the trees. On some plantations in East Java labourers are allowed to grow maize and beans under the trees in the rainy season.

Kapok requires little attention, but the soil must be kept weed-free by occasional hoeing and loosening. Fertilizers are not usually applied and no fertilizer experiments are known of. Pruning is not required.

Kapok is relatively free of diseases and pests. Stem-boring beetles (Plocordenes obesus) are a principal pest of the crop. The kapok pod-borer (Mudaria variabilis) can cause severe losses. Natural enemies reducing the damage are Anastasia sp. and Dorylus laevigatus. The young bud is sometimes bored by the larvae of Alcides leeuwenii.
Kapok can be severely damaged by parasites from the Loranthaceae. The only cure is to keep the soil bare around the tree.

In Java kapok is harvested from August to October. This period falls within the dry season, which is good for the quality of the kapok and also advantageous because very little labour is required for other crops at this time. The fruits are harvested when fully ripe and, in dehiscent types, before they open. Ripeness is indicated by the fruit colour changing from green to brown and the surface possibly becoming wrinkled. In plantations in Java the fruits are sometimes harvested before they are fully ripe to prevent theft. They are usually harvested by climbing the tree and using a knife or a bamboo pole with small hooks attached at the upper end to cut off the fruit. It is not economic to harvest the whole crop at once, as this will result in a mixture of ripe and unripe fruits. In Indonesia harvesting is usually done by the trader and seldom by the farmer.

Under optimum conditions a full-grown kapok plantation tree may yield 330—400 fruits per year, giving 15—18 kg fibre and about 30 kg seed. A satisfactory average annual fibre yield is about 450 kg/ha, whereas about 700 kg/ha is considered very good.

Inevitably, some immature kapok fruits will be harvested, but these are segregated and spread out on a drying floor and exposed to the sun, eventually turning brown and wrinkled. The fruits are hulled as soon as possible after harvesting. Drying is carried out in the wind or with fans in airy cage-like structures open to sunlight and covered with wire netting to keep the kapok from being blown away. The air movement caused by wind or fans also helps to separate the fibres from the seeds. Sometimes the kapok is spread on the ground in layers of 15—20 cm and prodded with long bamboo forks to loosen the clumps of fibre and expose the fibre to sunlight ('Jepara method').
The seeds lie loose in the floss, and therefore de-seeding is easier than it is for cotton. If de-seeding is done by hand, the floss is beaten with a stick and then screened, the operation being repeated several times. There are various types of de-seeding machines.
The quality of kapok is judged by fibre length, freedom from seeds and foreign matter, moisture content, colour, smell and lustre. In Indonesia the product is classified into 7 grades. 'Prima estate', 'Prima jepara', 'Average Java I', 'Average Java II' and 'C. min' are white-coloured and contain 1%, 1.5%, 2%, 3% and 5% dirt, respectively. 'C off I' is yellowish-white with 6% dirt and 'C off II' is yellowish.
When baling the kapok fibre for export, it should be borne in mind that excessive pressure will destroy the elasticity and diminish the quality of the fibre. The size of the bales exported from Indonesia depends on their destination: Singapore requires bales of 80 cm x 80 cm x 80 cm with a weight of 30—32 kg, Japan and Europe bales of 60 cm x 80 cm x 100 cm with a maximum weight of 100 kg, and the United States and Africa bales up to 130 kg.

In view of its pantropical distribution, kapok does not seem to be threatened with extinction. The small genetic variation of kapok in Asia indicates that the population was derived from only a few trees.
The largest kapok germplasm collection is kept at the Indonesian Tobacco and Fibre Crops Research Institute in Malang (Indonesia) and contains 180 accessions. Of these, 59 are the result of crosses in the colonial period, 88 are local clones and 33 are from explorations in several kapok areas in the 1990s. Some accessions are held at CNSF (Centre National de Semences Forestières) in Ouagadougou (Burkina Faso).

There is little breeding of kapok. The breeding carried out aims at high production of high quality kapok fibre. Since the fibre has to compete with synthetic substitutes, it could be argued that a type should be produced which is either cheaper or better than its synthetic counterparts. The substitutes are produced in countries which used to import kapok, thus freeing these countries from reliance on kapok. It would be better to gear breeding programmes to the home demands of kapok-growing regions or countries. Selection or crossing could result in higher-yielding types and types producing a better kapok, for instance with longer fibre cells. To this end, indigenous and foreign material should be screened to obtain the desired characteristics. Artificial pollination can be done by hand. Emasculation should be done in the afternoon and pollination at night or early in the morning. Kapok pollen can be stored at room temperature for several days only. The success rate for crosses is usually 15%. Some selection work has recently been carried out in Thailand. Superior trees obtained by selection or crossing can be multiplied by means of vegetative clonal propagation.

Kapok's importance in international trade will remain very limited. The kapok tree will continue to have some importance in South-East Asia as a multipurpose tree for local use, grown for its fibre and seed, as a reforestation tree, for fuel and for shade. If breeding activities are resumed, they should be directed towards local requirements.

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M. Sahid & A.C. Zeven

M. Sahid & A.C. Zeven, 2003. Ceiba pentandra (L.) Gaertn.. In: Brink, M and Escobin, R.P. (Editors): Plant Resources of South-East Asia No 17: Fibre plants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea