Traditional vegetables in Zambia: genetic resources, cultivation and uses

D.S. Mingochi and S.W.S. Luchen
Department of Agriculture, National Irrigation Research Station, Mazabuka, Zambia

Introduction

Traditional or local vegetables include many species which are wild, semi-cultivated or are protected in some way. They may also include species mainly cultivated for their pods, fruits, roots or tubers, but whose leaves are sometimes consumed as a vegetable. The majority of rural people in Zambia rely on traditional vegetables for their relish. In a rural survey, it was found that traditional vegetables were used by 52-95% of the respondents (Ogle et al. 1990). The diversity in traditional vegetables offers variety in family diet and helps ensure household food security. More than 175 different species have been documented as local vegetables in Zambia (Johansson 1989; Ogle et al. 1990). Among the more prominent species are Amaranthus spp., Cleome spp., Corchorus spp., Disa satiria, Solanum aethiopicum/macrocarpon, Ipomoea spp., cassava, Zanthoxylum chalybeum, various cucurbits and Ceratotheca sesamoides. Apart from the major species, there are a large number of 'minor' vegetables known by fewer households and used less frequently. Many traditional vegetables are specific to particular areas and ethnic groups. Notes on the genetic resources, cultivation and use of some local vegetables are given below.

Genetic resources of traditional vegetables

Vegetables have received comparatively low priority since the inception of Zambia's National Plant Genetic Resources Centre in the early 1980s. Emphasis has been directed toward the major traditional staple food crops, such as Sorghum bicolor, Eleusine coracana, Pennisetum americanum, Zea mays, Vigna unguiculata, Arachis hypogea, Phaseolus vulgaris and Vigna subterranea. These represent 50% of the total collection. Only a few accessions of some vegetable species (Amaranthus spp., Corchorus spp., Solanum spp., Cleome gynandra, Abelmoschus esculentus and Brassica spp.) are conserved in the national genebank. Not enough has been done in terms of inventory, collecting, characterization and documentation.

However, some preliminary work has been done and priority species identified. Diversification being a priority in the national food strategy, it is important to complete the inventory and collect representative material that can be made available for improvement and domestication.

Traditional farming systems have played an important role in preserving genetic diversity (MAFF 1995). Most traditional cultivation practices include passive conservation of semi-cultivated or wild relish species. The future plans of the national plant genetic resources programme include the establishment of community-based conservation activities, which may require technical and financial assistance from the national, regional and global levels.

A vegetable crops working group is in place in Zambia to advise the national programme on technical issues. A meeting was also held recently to form a regional working group on vegetables. The mandate of the regional working group includes the planning and monitoring of conservation work on vegetable species.

The manner in which certain traditional vegetable species are exploited makes them vulnerable to extinction. This is especially true of the root vegetable and shrub species whose harvesting involves destroying the entire plant. There are threats of extinction due to land clearing for agriculture, urbanization and overgrazing. Unfavourable weather conditions such as droughts and extreme temperatures have been experienced in recent years and these have affected populations of some semi-wild and wild species. Traditional vegetables are often associated in people's minds with backwardness and feeding habits have therefore been changing of late in favour of exotic vegetables. There is generally inadequate knowledge on the importance (e.g. nutritional) of vegetables, leading to neglect. Most traditional vegetables are specific to areas and ethnic groups and are highly seasonal. All these attributes render them less attractive to development efforts, including conservation activities.

There is a need to mobilize staff and financial resources at the national level to strengthen the activities of inventory, collecting, characterization, evaluation and documentation of traditional vegetables. For this, capacity-building will be needed in the areas of botany, taxonomy and biotechnology. Promotion of community participation and public awareness of genetic resources and other biological diversity issues needs to be stepped up at the same time. International and regional collaboration will be required to develop effective strategies for conservation.

Cultivation and use of traditional vegetables

Amaranthus spp.
Bondwe, Lengalenga (B); Libowa (Lo); Bonongwe (N); Bonko (T)¹

¹ The letters stand for local languages as follows: (B) Bemba, (L) Luvale, (Lo) Lozi, (N) Nyanja, (T) Tonga.

Use. Terminal shoots and tender leaves are eaten in much the same way as spinach. Leaves may be dried and stored for use in deficit periods. Two local selections of A. cruentus - UNZA A₁ (dark-seeded) and UNZA A₂ (white-seeded) - are being sold commercially by the Zambia Seed Company.

Importance. Leaves are a source of protein and vitamins A and C. They are also rich in the minerals calcium, potassium and iron. Amaranth is an easy crop to propagate as it has the capacity to produce abundant seed. It is a readily available vegetable in the rainy season, when exotic vegetables become scarce. It is widely sold in urban markets, and thus generates income with minimal inputs. It is consumed throughout eastern Africa (FAO 1988).

Cleome gynandra
Lubanga (B); Sishungwa (Lo); Suntha (N); Shungwa (T)

Cultivation. Cleome occurs wild, as a weed of arable lands or as a semi-cultivated species. Plants growing among field crops are usually left undisturbed at weeding. Mature seeds are at times collected from these plants at the end of the rainy season. When the next rainy season commences, the seeds are broadcast on rubbish dumps near homesteads. It is grown in association with other traditional vegetable species or in pure stands. At times, seeds are broadcast in localized spots of high soil fertility in cereal crop fields. In pure stands, thinning is done at 4 weeks after sowing where density is too high. Weeding may be carried out in the early growth stages to encourage vigorous growth, which is desirable in reducing the bitterness of leaves, making them more palatable. Picking of leaves and shoots commences in the sixth week after sowing. A number of pests, including beetles and Harlequin bugs (Bagroda hilaris), attack the crop. Control measures include spraying with insecticides and dusting with ash.

Use. Fresh leaves and tender shoots are boiled whole or chopped and mixed with groundnut flour and other ingredients to produce a tasty relish. Preservation of leaves is done by blanching followed by sun-drying. Two different types of this annual herb, distinguished by stem colour (green and purple), occur in Zambia. Both types are used. A local selection is being marketed commercially.

Importance. Leaves are rich in vitamins A and C, and contain moderate levels of calcium and iron. Cleome is a widely consumed and popular vegetable in rural areas. It is commonly sold in urban markets during periods of abundance.

Corchorus spp.
Lusakasaka (B); Tindingoma (N); Delele, Cikombo bbuyu (T)

Cultivation. This vegetable has a wide distribution in Zambia, but is mostly found in areas receiving less than 1000 mm of rainfall per annum (Vernon 1983). Two species occur, both of which are used as vegetables - C. olitorius and C. tridens. They grow wild or as weeds of cultivated lands, and have wide adaptability to soil types. The plant grows and is gathered in the rainy season, though it is also common during summer months in irrigated fields. Villagers tend to protect Corchorus plants growing as weeds among cultivated crops. Harvesting starts when plants are 20-30 cm high. Leaf yield is increased by removal of the terminal shoot. Picking can continue for up to 3 months. Fertilizer trials indicate that the plant does not show an appreciable response to nitrogen, evidence of its adaptation to low-nitrogen conditions (Vegetable Research Team 1985). No major pests or diseases have yet been reported in Zambia.

Use. Tender fresh shoots mixed with soda and with added salt are cooked to produce a relish of slimy and slippery consistency. Fresh leaves are sun-dried either whole or pounded to preserve them for future use. As a common practice, whole plants are dried in the shade and the leaves removed later.

Importance. Fresh leaves are a source of vitamins A and C. The small amounts of protein present are rich in methionine. This is a popular local vegetable in rural areas. The mucilaginous property of the preparation makes it easy to take with starchy staple foods, usually nshima (thick maize porridge).

Solanum macrocarpon, S. aethiopicum
Impwa (B); Zhilo (L)

Cultivation. These sturdy herbaceous annual or perennial crops are most commonly found in the northern, high-rainfall areas of the country, although they are now spreading to other areas. Production is mainly in the rainy season (November-March) for the rural areas, but a few peri-urban gardeners do grow the crop under irrigation during the dry season (April-October). Growers in the villages collect seed from the preceding crop. Seed extraction involves fermenting longitudinally cut mature fruits (4 weeks from set) to facilitate separation from the pulp. Fermentation is by soaking the fruit in water for 1-2 days. Seeds are then squeezed out by hand. The seeds are then dried in the shade and stored in calabashes for the following season's planting. Seeds may show dormancy a few weeks after extraction. Under this system of cultivation, the seed is broadcast near homesteads in pure stands or in mixture with other traditional vegetable species. Where the crop is commercialized in the peri-urban areas of the Copperbelt, seedlings are raised in nursery beds and later transplanted. The crop is planted in pure stands in gardens at a spacing of 100 x 30 cm. Commercial fertilizers and manure are used in much the same way as for the European eggplant (Solanum melongena).

Use. Only the unripe fruits are eaten. These are chopped up and cooked with cooking oil or soda and used as a relish. They may be prepared together with other vegetables. The immature fruits are at times eaten raw. Fruits are preserved for future use by sun-drying.

Importance. The fruits are a source of small amounts of starch and protein and appreciable amounts of vitamin A and iron. It is a remunerative crop, as it is a popular vegetable sold on streets and markets in urban areas. A few growers have been exporting the crop.

Zanthoxylum chalybeum
Pupwe, Pupwe chulu (B)

Use. This is a wild perennial shrub/tree limited to the high-rainfall areas of northern Zambia. It is usually found growing on ant hills. Because of the prickly protuberances covering the trunk, villagers tend to cut down the whole plant to pick the fresh leaves and tender shoots. This practice appears to be threatening the very existence of this species in some areas. Most of the big trees close to human settlements have been cut down. In such localities, people have to travel long distances in search of the plant. Fresh leaves are first dried and then pounded in a mortar to a fine powder. Water and soda are added, then the mixture is warmed to produce a relish of very strong flavour and mucilaginous consistency. Preserving leaves for future use involves smoking or sun-drying after pounding to powder form.

Importance. This is a popular vegetable but has become rather a delicacy in some localities owing to difficulties in procuring it. It is reported to have been an important relief food in years of famine.

Manihot esculenta
Kalundwe (B); Mwanja (Lo) (T)

Cultivation. Cassava has wide adaptability to varied soil conditions. Commercial fertilizers are not usually used. Propagation is by stem cuttings at the start of the rainy season. Plantings are either in pure stands or in mixtures with other crops like finger millet, sorghum, maize and cucurbits (the last being most common). Leaf harvesting commences once the plant is established and continues for a couple of years.

Use. Primarily grown for its tubers, leaves are also an important vegetable. It is in fact regarded as one of the most convenient vegetable species. Leaves and tender shoots are chopped or ground and boiled with groundnut flour, fats or fish to make a relish. Leaves are at times preserved for future use by drying either in the shade or in direct sunlight.

Importance. Cassava provides a full meal of starch from the tubers ground as flour and a protein-rich relish from the leaves. The leaves are rich in vitamin A. It gives insurance in food security because of its suitability in marginal conditions, partly owing to its ability to shade its leaves in stress periods and quickly rejuvenate when conditions improve.

Ipomoea batatas
Kalembula (B); Ngulu (Lo); Chimbwali (T)

Cultivation. The sweet potato is widely cultivated in the rainy season, primarily for its tubers. Propagation is by stem cuttings planted on mounds about 30 cm high. Commercial fertilizers are not usually used, but surrounding vegetation is generally buried in the mounds. In urban gardens under irrigation, the crop is now grown throughout the year to provide leaves for relish. Leaves are picked over several months. Leaves of wild Ipomoea spp. are also utilized as vegetables. Sweet potato has a few serious pests, such as sweet potato weevil.

Use. The leaves may be mixed with groundnut flour, fats or dried fish or meat. They are preserved for use by blanching followed by sun-drying or may be dried directly in the sun.

Importance. Fresh leaves are a good source of proteins, calcium and iron and are moderately rich in vitamin C. They are sold in urban markets and provide a reliable source of green leafy material in the rainy season.

Cucurbita maxima and other species
Fipushi (B); Lupusi (T); Namundalangwe (Lo)

Cultivation. Pumpkins and other cucurbit species, such as local cucumber and melons, are grown mainly for their fruits during the rainy season, usually intercropped with other field crops such as cereals and cassava, although they are also commonly planted with other traditional vegetables on old cattle kraal sites, waste dumps or on ash sites where trees have been burned during land clearing. Farmers usually extract their own seeds from mature fruits after harvesting and store them for later use. Seeds are directly sown a few centimeters below the soil surface. Picking of pumpkin leaves only commences after the plant has started to fruit. Defoliation for relish may continue for several months where interference from pests and diseases is low because plants continue producing new leaves sometimes long after the rainy season is over.

Use. Leaves and young fruits are boiled and mixed with various ingredients and used as a relish. Leaves are commonly chopped or pounded and mixed with groundnut flour or cooking oil. Smoked or sun-dried leaves can be stored for a long time for future use.

Importance. Fresh pumpkin leaves are rich in calcium, protein and vitamin C. Dried leaves are high in protein and iron and moderately high in vitamin C. This is a very popular vegetable in both rural and urban areas, and is sold in urban markets during periods of abundance. When exotic vegetables are scarce in the rainy season, pumpkin leaves provide a reliable alternative source. It fits well in mixed cropping systems found in many parts of Zambia.

References

FAO. 1988. Traditional food plants. Food and Agriculture Organization of the United Nations, Rome, Italy.

Johansson, E. 1989. Cultivated, semi-cultivated and wild leaf-vegetables used in Zambia. A pilot investigation for the regional SADCC genebank programme. A minor field study. Working Paper No. 119. International Rural Development Centre, Swedish University of Agricultural Sciences, Uppsala.

MAFF. 1995. Present Status of Plant Genetic Resources in Zambia. Country report for the International Conference and Programme on Plant Genetic Resources. Compiled by W.M. Mwale, G.P. Mwila, E.D. Zulu, D.S. Mingochi and W. Chita.

Ogle, B., L. Malambo, D.S. Mingochi, I. Malasha and A. Nkomesha. 1990. Traditional Vegetables in Zambia. A study of procurement, marketing and consumption of traditional vegetables in selected urban and rural areas in Zambia. International Rural Development Centre, Swedish University of Agricultural Sciences, Uppsala, Sweden.

Vegetable Research Team. 1985. 7th Annual Report of the Vegetable Crops Research Team. Ministry of Agriculture and Water Development. Lusaka, Zambia.

Vernon, R. 1983. Field Guide to Important Arable Weeds of Zambia. Balding and Mansell Ltd., London and Wiesbech, England.