Cola Schott (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Cola Schott & Endl.

Protologue: Melet. bot.: 33 (1832).

Family: Sterculiaceae

Chromosome number: x= 10; 2n= 40 (C. acuminata,C. nitida)

Major species and synonyms

• Cola acuminata (P. Beauv.) Schott & Endl., Melet. bot.: 33 (1832), synonyms: Sterculia acuminata P. Beauv. (1804), Sterculia macrocarpa G. Don (1831), Cola macrocarpa (G. Don) Schott & Endl. (1832).

• Cola nitida (Vent.) Schott & Endl., Melet. bot.: 33 (1832), synonyms: Sterculia nitida Vent. (1804), Cola vera K. Schum. (1900), C. acuminata (P. Beauv.) Schott & Endl. var. latifolia K. Schum. (1900).

Vernacular names

• General: kola, kola nut tree, cola (En). Colatier, kolatier (plant), noix de cola (product) (Fr)
• Indonesia: kola
• Vietnam: cô ca.

• C. acuminata : Abata kola (En). Kolatier sauvage (Fr).

• C. nitida : Gbanja kola, bitter cola (En).

Origin and geographic distribution

Cola has its centre of diversity in West Africa. There are three areas with relatively greater concentrations of species: Sierra Leone/Liberia, Nigeria/Cameroon and Gabon. C. nitida , the common kola, originated in West Africa in the region of Sierra Leone to Benin, and has its main area of distribution in the rain forest area of Ivory Coast and Ghana. The distribution area of C. acuminata is further east: from Togo to the rain forest areas of eastern Nigeria, Cameroon, western Democratic Republic Congo and Angola.

The kola nut (botanically not a nut, but the seed, usually with 2 ( C. nitida ) or 3-6 ( C. acuminata ) cotyledons) was taken to many parts of the tropics by traders, although large-scale cultivation remained limited to West Africa. C. nitida was reported from Trinidad and Jamaica as early as 1680, and also from India, Indonesia, Peninsular Malaysia and Singapore in the early 19th Century. It occurs in Australia and is widespread in South America. C. acuminata has been reported from Brazil, Venezuela and Colombia. Both species were probably introduced into Central and South America during the times of the slave trade.

Fresh kola nuts have long been an important commodity in the northern savanna region of West Africa and trade in kola nut was common. From the 17th Century onwards nuts were shipped along the West African coast from the more westerly areas towards the harbour of Lagos in Nigeria and then inland to northerly areas. This intensive trading was later stimulated by the establishment of road and rail connections, which led to C. nitida cultivation being introduced in the hinterland of Lagos harbour, to replace the occasionally grown C. acuminata . The result was unprecedented growth in the production of C. nitida nuts, virtually all for export towards the northern savanna areas, thus replacing imports. C. acuminata remained of local interest only.

In Indonesia, C. nitida trees were used for shelter-belts early in the 20th Century, and were intercropped with cocoa on Java and Sumatra. Although growth was satisfactory and nuts were produced, no trade developed in the nuts and later most of the trees were felled to provide more space for cocoa. However, some large kola trees still remain and kola is sometimes still used as a shade tree in young cocoa and coffee plantings. The wood is used for small carpentry objects and construction.

Uses

Chewing fresh kola nuts (seeds) has a pleasant stimulating effect. Locally, dried nuts are sometimes used for the preparation of stimulating infusions. In West Africa, kola nuts play an important role in social life, ceremonies (e.g. weddings) and religious customs. In traditional medicine they are used as a stimulant, tonic and astringent. The trees yield durable wood, which is used to make canoes. Extracts from dried C. nitida nuts have been added to beverages; the cola soft drink originally included extracts from Cola nitida and coca ( Erythroxylum coca Lamk or E. novogranatense (Morris) Hieron.). Most of the kola for this purpose was obtained from South and Central America; no interest was shown in West Africa for the trade in dried nuts, as the trade in fresh ones for immediate use for chewing proved much more lucrative. Cola soft drinks are nowadays usually prepared from artificial cola flavourings, caffeine, and coca leaves from which the cocaine has been removed.

Production and international trade

West Africa is the major player in kola production and trade. In the early 20th Century, world total annual production was around 20 000 t, 75% of which was accounted for by C. nitida . In the 1960s annual production rose to 175 000 t, of which 120 000 t came from Nigeria, 50 000 t from the area between Sierra Leone and Benin and some 3000 t from South and Central America (with a Jamaican production of about 1000 t). In the 1980s total production rose to 200 000 t per year with a similar distribution. Elsewhere, kola was not registered in production statistics. West African kola is mainly produced by smallholders.

At the retail level in West Africa fresh kola nuts are priced individually. In 1995 the price was at the equivalent of US$ 0.04-0.08 depending on the size of the nut. As the average weight of fresh nuts is around 17 g, the value per t of fresh nuts was equivalent to about US$ 3500. Dried nuts intended for the preparation of beverages command a much lower price: in the 1960s and 1970s this was 10% of current prices when calculated on a fresh weight basis.

Properties

Kola nut mainly owes its stimulating effect to the rather high caffeine content, which in the fresh nut occurs partly in association with catechin and with tannins. It is not known how far the stimulating effect is influenced by other alkaloids present in much smaller quantities, such as theobromine and betain. Dry C. nitida nuts contain per 100 g: water 16 g, protein 11 g, fat 2 g, carbohydrates 52-53 g, fibre 8-9 g, caffeine 1-3 g, tannins 4 g and ash 3 g. When masticated, the tannins of the fresh nut are astringent in the mouth, though this soon disappears and turns to a sweet taste as the tannins lose their effect. At the same time the alkaloids are released by the influence of enzymes and provide their stimulating effect.

Oral tumours and gastro-intestinal malignancies occur relatively often in regions where kola nut chewing is common, especially in northern Nigeria, and it has been suggested that kola nuts may be carcinogenic because of their high tannin content or the presence of other carcinogenic compounds, such as amines.

The 1000-seed weight is 500-3500 g.

Description

Evergreen trees, mostly small or medium in size. Leaves alternate or whorled, simple or digitately compound, entire or lobed, petiolate. Inflorescence an axillary raceme, panicle, cluster or whorl, usually with male and bisexual flowers; calyx widely campanulate, deeply 4-6-lobed, white or coloured; corolla absent; male flower with androphore bearing 5-20 stamens which are joined in a column; bisexual flower with a gynandrophore, bearing a single or double ring of 5-6 anthers each at the base of the ovary, ovary with several (usually 5) coherent carpels and free styles. Fruit composed of 4-5 longitudinal dehiscing follicles. Seeds up to 14 per carpel, obtuse-angular, up to 5 cm × 3 cm, with 2 or more cotyledons and no endosperm.

• C. acuminata : slender tree, 7-10(-13) m tall, often branching near the base. Leaves alternate but sparse and confined to tips of branches; petiole about 4 cm long; blade elliptical to oblanceolate, 16(-27) cm × 5.5(-11) cm, rounded at the base, at apex acuminate and often twisted downwards, dark green, rather fleshy, often curled, lateral veins not prominent. Inflorescence several- to many-flowered, flowers not whorled, rotate; bisexual flower up to 2.5 cm in diameter, male flower smaller; calyx lobes united for nearly half their length, white with red splash inside at base. Fruit composed of up to 5 follicles; follicle sessile, at right angles to peduncle, horizontal, 20 cm × 6 cm, not knobbly, rough to touch, with up to 14 seeds, brownish. Seed up to 4 cm × 2.5 cm, with a thin, white testa, with 3-6 pink, red or sometimes white cotyledons.

• C. nitida : robust tree, 8-12(-25) m tall; bole up to 4(-12) m long, up to 50 cm in diameter, with narrow buttresses up to 1 m high; crown dome-shaped; bark fissured longitudinally, grey. Taproot reaching 120 cm in depth; lateral roots developing profusely in top layer of the soil, largely in the first 15 cm, extending to about 5 m from the trunk; sinker roots penetrating up to 1 m are formed on the lateral roots. Leaves alternate, simple, not confined to tips of branches; petiole 1-10 cm long, with a prominent pulvinus at base and top; blade broadly oblong to broadly elliptical or sometimes elliptical-oblanceolate, 9-32 cm × 3.5-13 cm, cuneate to rounded at base, shortly acuminate at apex, glabrous or nearly so. Inflorescence an axillary panicle of cymes with 5-merous flowers; calyx slightly cup-shaped, lobes united up to about one third, white or cream with a small red mark at base, puberulous outside; male flower up to 2.5 cm in diameter; androecium composed of 2 whorls of 10 pollen sacs each, reddish, on a short androphore of 1 mm; gynoecium rudimentary; bisexual flower 3-5 cm in diameter; androecium reduced, superimposed by the 5 carpels, each with 10-12 ovules, style short, stigmas radiating, linear. Fruit composed of 5(-6) follicles on a short peduncle; follicles horizontal or recurved, roughly ovoid, 8-13 cm × 4-8 cm, with a short curved beak, knobbly, dehiscing along the ventral suture, with 4-8(-10) seeds, green. Seed up to 5 cm long, with a tough, white to pink testa, with 2(-3) white, pink or red cotyledons.

Growth and development

Kola seed passes through a dormancy period of some weeks to several months. When planted after the dormancy period, it germinates within a few weeks. At this time the radicle emerges from amongst the cotyledons and at the same time the hypocotyl elongates and pushes out the plumule. Subsequently, the root elongates rapidly, 8 cm within the first week, and the plumule straightens out. Thereafter, growth slows down; the root depth is 15 cm after 9 weeks. Shoot growth shows a similar pattern: 1-2 weeks of rapid growth (6-11 mm per day) followed by slower growth (1-2 mm per day). The cotyledons remain turgid and are retained for up to 9 months after germination as a store of reserves. The seedling develops monopodially until the 3rd-4th year when it changes to the adult phase with sympodial growth and discontinuous growth in "flushes". The terminal buds remain dormant, abort or develop into a shoot with one or few leaves at the time of the next flushing period. The tree may flower from this time onwards, but usually not until the 6th-7th year. Regular flowering occurs once a year. In Nigeria, C. nitida flowers in the rainy season in July and August and its fruits become available in November, whereas C. acuminata flowers in the dry season from December to February, giving fruits in April or May. C. nitida in Java has been reported to flower throughout the year. The number of hermaphrodite flowers per inflorescence seems to diminish with their position on a flush, the more apical inflorescences having fewer hermaphrodite flowers. The hermaphrodite flowers are receptive for some 4 days; the male ones produce viable pollen mainly the first two days of anthesis. It is thought that the sticky pollen may be transferred by a midge ( Forcipomyia sp.). Artificial pollination has revealed that kola may be self- or cross-incompatible. When applied in certain combinations the success of artificial pollination proved to be as high as 33%. Fruits mature in 120-135 days, and full production is achieved when trees are 15-50 years old. C. acuminata produces flowers and fruits in the Bogor Botanical Garden in Java.

Other botanical information

The genus Cola comprises some 125 species and has been subdivided into 5 sections. The section Cola includes the species with edible seeds. The seeds of certain cultivated kola species other than C. acuminata and C. nitida are also used as a stimulant, e.g. C. anomala K. Schum. ("Bamenda kola") from Cameroon and C. verticillata (Thonn.) Stapf ex A. Chev. ("Owé kola") from the rain forest of West and Central Africa.

Ecology

Wild kola occurs in the West African rain forest. Kola needs a regular supply of water and is usually found in areas with more than 1250 mm annual rainfall in at least eight rainy months (>50 mm of rain), unless water is available from other sources. Temperatures in the range of 25-30°C and high relative humidity are favourable; low relative humidity may lead to leaf shedding. Kola is commonly planted on red ferrallitic or ferruginous soils, and does not tolerate waterlogging. Young kola plants need overhead shade.

Propagation and planting

Kola is usually propagated by seed. Nursery-raised plants lead to a more complete stand in the orchard than seeds sown at stake. Seed for propagation should be as large as possible, as this strongly influences the rate of development. C. acuminata seed has been reported to germinate faster than that of C. nitida . Seed should be sown in the nursery about 6-12 months before the start of the rainy season, depending on the length of seed dormancy, to allow for transplanting in the early part of the rainy season. Seed may be planted 5-10 cm deep in a horizontal position. To speed up germination it should be placed on top of a moist planting medium, covered with polythene and illuminated. Pre-germinated seed should be potted with the cotyledons exposed. As seedlings depend on their taproot for up to 9 months, containers should be 40-45 cm deep; otherwise, plants should be raised in a seedbed. When 12 months old, seedlings will have developed secondary roots and be capable of being transplanted with a desirable rootball. At transplanting, seedlings should be about 50 cm tall and have 12-14 expanded leaves. Seedlings that have been in the nursery for up to 12 months carry 17-20 leaves, and should be pruned back to 50-60 cm.

Propagating high-yielding trees through stem cuttings is a useful method, with up to 90% success, but the results for individual trees may vary considerably. Rooted cuttings ("ramets") from plastic-covered rooting bins need to be hardened off during their nursery period prior to transplanting. Such plants remain in their adult, sympodial growth pattern and are capable of immediate flower formation. Young trees are planted out at spacings of 7.5-9 m × 7.5-9 m, depending on soil fertility. When establishing an orchard with ramets, which are productive within two years, it is advisable to use spacings of 3.5-4.5 m × 3.5-4.5 m and to thin out trees in the sixth year to achieve optimum plant density.

Husbandry

Though kola benefits from light shading, during the first two years of its development, it needs sunlight thereafter and a guaranteed supply of adequate moisture in order to develop well. It is essential to keep an area of 80-100 cm around the stem of young kola plants free from weeds. To avoid root damage, the use of tools in this circle should be restricted. Mulching of the ring around the young plant promotes the development of lateral roots and provides the required soil protection, which is later given by the canopy of the tree itself.

The removal of nutrients through the harvested kola nuts is quite small: for a very high production level of 3 t/ha it amounts to 13 kg N, 10 kg K, 2 kg Mg and 1 kg P. The use of fertilizers is therefore not advised, unless specific soil problems arise.

Diseases and pests

On clear-felled land young kola plants may be affected by a root disease caused by Fomes lignosus and F. noxius . However, the main losses from fungal diseases may occur if nuts have been freshly harvested and are not handled properly during their dormancy period. Kola trees may be attacked by the kola stem borer ( Phosphorus spp.); coppicing and regeneration may then be required. Kola fruit fly ( Ceratitis colae ) may cause serious losses in the number of fruits. Severe problems are caused by curculionid kola weevils ( Balanogastris kolae and Sophrorhinus spp.). These ravage kola nuts before harvest but cause even more serious damage later, which is why it is essential to remove any affected nuts from stored lots.

Harvesting

Fruits of C. nitida should be cut before dehiscence, to prevent insect attack. Any fallen fruit should be picked up immediately. The follicles are opened and the seeds, in their fleshy seed-coat, are put in heaps that are frequently sprinkled with water. The seed-coat then decays rapidly and after some days the nut can be wiped off, leaving the nut clean and without any external injury that would reduce its value.

Yield

Yields of C. nitida range from 500-1000 kg of fresh kola nuts per ha, i.e. 200-400 nuts per tree (being 5-10 fruits). Observations have indicated that most of the production is obtained from only a few trees in a given population. Individual trees, observed in Nigeria for 7-10 years, have produced on average up to 1872 kola nuts per year.

Handling after harvest

The kola nuts are kept in baskets and are regularly stirred and checked for insect damage. During this period, which lasts several days, the nuts dry out and go into dormancy. They are then placed in baskets lined with fresh leaves, which are replenished at intervals of 2-3 weeks. It has been suggested that polythene sheet may replace the green leaves as lining for containers once the nut has entered dormancy. Keeping nuts in airtight containers may further reduce metabolism because of the build-up of CO₂, and, in addition, prevent development and attack by kola weevils.

In Indonesia and South America, the harvested seeds are usually treated like those of cocoa. Sometimes they are even dried artificially, as the appearance of the product is unimportant here.

Genetic resources

There are no known substantial germplasm collections of C. acuminata and C. nitida .

Breeding

Highly productive trees of C. nitida in Nigeria have been intercrossed and the resulting progenies planted in di-allele cross experiments. Early results have confirmed that the most productive cross is AA 231 and that it has potential as a parent for future selections. Combining selection with clonal propagation of the best trees is proving to be a fruitful strategy. Large-scale selection of outstanding trees in western Nigeria from about 150 000 trees on 537 farms, followed by observations on yield performance during 4 years, has led to the identification of 140 trees as potential heads of clones. These selected trees showed an average yield of 1750 nuts per tree over 4 years and about 40% of them were successfully propagated by cuttings.

Prospects

The future of kola depends very much on the improvement of its productivity per unit of land. It seems possible that productivity could be tripled or quadrupled by selecting suitable parent trees for clonal propagation. Controlled pollination may further advance productivity. If these improvements are realized, a possible consequence could be a reduction of the area under kola in the current production areas. Although growth and production are satisfactory in South-East Asia, especially Indonesia, the prospects for expansion in the region are not very good, because of the availability of other stimulants like areca nut, coffee and tea.

Literature

• Agiri, B., 1981. Kola-Handel in West Afrika [Kola trade in West Africa]. In: Völger, G. (Editor): Rausch und Realität, Drogen im Kulturvergleich (Intoxication and reality, drugs in culture comparison. Rautenstrauch-Joest Museum, Cologne, Germany. pp. 528-532.
• Atawodi, S.E., Mende, P., Pfundstein, B., Preussmann, R. & Spiegelhalder, B., 1995. Nitrosatable amines and nitrosamide formation in natural stimulants: Cola acuminata, C. nitida and Garcinia cola. Food and Chemical Toxicology 33(8): 625-630.
• Bodard, M., 1962. Contribution à l'étude systématique du genre Cola en Afrique occidentale [Contribution to the systematic study of the genus Cola in West Africa]. Annales de la Faculté des Sciences de l'Université de Dakar. Vol. 7. 182 pp.
• Germain, R., 1963. Sterculiaceae. Cola. In: Comité exécutif de la flore et par le jardin botanique de l'état (Editors): Flore du Congo, du Rwanda et du Burundi. Vol. 10. Institut National pour l'Etude Agronomique du Congo Belge, Brussels, Belgium. pp. 277-316.
• Hunger, F.W.T., 1918. Kola. In: Prinsen Geerligs, H.C. (Editor): Dr. K.W. van Gorkom's Oost-Indische cultures [Dr. K.W. van Gorkom's East-Indian cultures]. 2nd edition. Vol. 2. J.H. de Bussy, Amsterdam, the Netherlands. pp. 587-630.
• Russell, T.A., 1955. The kola of Nigeria and the Cameroons. Tropical Agriculture (Trinidad) 32: 210-240.
• van Eijnatten, C.L.M., 1969. Kolanut (Cola nitida Schott & Endl. and C. acuminata Schott & Endl.). In: Ferwerda, F.P. & Wit, F. (Editors): Outlines of perennial crop breeding in the tropics. Miscellaneous Papers No 4, Wageningen Agricultural University, Wageningen, the Netherlands. pp. 289-307.
• van Eijnatten, C.L.M., 1969. Kola: its botany and cultivation. Communication No 59 of the Department of Agricultural Research. Royal Tropical Institute, Amsterdam, the Netherlands. 100 pp.
• van Eijnatten, C.L.M., 1977. Report on a study of kola nuts in Zaire (7-17 February 1977). Department of Crop Science, Faculty of Agriculture, University of Nairobi, Kenya. 23 pp.
• van Veen, H.A.G., Awonusi, R.O., Fürste, L.J., Odusolu, E.O., van Eijnatten, C.L.M. & Olaniran, Y.A.O., 1977. Final report Kola Pilot Project, September 1970-April 1976. Ministries of Economic Development and Agriculture, Ogun State, Nigeria & International Technical Assistance Department, Ministry of Foreign Affairs, The Hague, the Netherlands.

Authors

C.L.M. van Eijnatten & Roemantyo