Conservation and use of traditional vegetables in Zimbabwe

F. Ckigumira
Horticultural Research Centre, Marondera, Zimbabwe

Introduction

Zimbabwe is a land-locked country lying between 15° and 22°S latitude and from 26° to 34°E longitude. It is bounded by the Zambezi river in the north and the Limpopo river in the south. Three major regions are generally recognized on the basis of altitude. These are the Lowveld (below 900 m asl), the Middleveld (900-1200 m asl) and the Highveld (1200-2000 m asl). Only the Eastern Highlands, consisting of a narrow belt of mountains and a high plateau, are above 2000 m asl. One-fifth of the land is over 1200 m asl and three-fifths between 600 and 1200 m asl. Thus, though Zimbabwe lies in the tropics, only the low-lying Zambezi and Limpopo valleys experience tropical conditions. Most of the country has a subtropical climate. The soils are predominantly sandy with heavier loamy and clay soils occurring in relatively localized areas.

Zimbabwe has an erratic seasonal rainfall occurring mainly in the summer months of November to March. A pronounced dry season occurs from May to October. Only 37% of the country receives more than the 700 mm annual average considered necessary for semi-intensive farming (Nyamapfene 1991). The natural growing season is confined to the rainy months and both the total rainfall and its distribution over the season are the limiting factors in agriculture, both being very unreliable. In general, rainfall decreases from east to west and from north to south. The country has been divided into five agro-ecological zones in terms of agricultural potential (Nyamapfene 1991).

Land was divided on racial grounds in the early colonial days into communal lands, small-scale commercial and commercial (see Table 1). The commercial farms were owned by white settler farmers and had the best of the land in terms of soils, rainfall and vegetation. The communal areas, where more than 75% of the population lives, are overcrowded in terms of both human and cattle populations, have very poor soils and suffer erratic and unreliable rainfall. This scenario has not changed much despite the political changes that have taken place since 1980.

Table 1. Land allocation in Zimbabwe.

Sector	Area (ha)
Commercial farming areas	16 600 000
Communal farming areas	16 300 000
National land (parks, etc.)	5 900 000
Urban areas	200 000

The role of traditional vegetables in the lives of people in communal areas

During the rainy season (November to March) the main constraint on horticultural production is the high incidence of insects and diseases. From April to August, covering the winter season (May-July), vegetables are produced in plenty by those who have irrigation facilities or access to dambo gardens (wetlands). From August to the end of December the availability of vegetables becomes very limited to people in communal areas. During September and October temperatures are highest and evapotranspiration is at maximum. Most gardens are dry and field vegetables will still be unavailable. People buy cabbages and use the reserves of dried vegetables they prepared in times of plenty. These dried vegetables include both exotic and traditional species. Thus, people in communal areas rely on traditional vegetables during the 5 months of the rainy season and during the 4 summer months, or three-quarters of the year.

Below are listed the main cultivated species used as leafy vegetables, of which pumpkins and cowpeas are perhaps the most important:

· pumpkin leaves (Cucurbita maxima)
· cowpea leaves (Vigna unguiculata)
· okra (Abelmoshus esculentus)
· tsunga (Brassica juncea)
· chembere dzagumana (Brassica carinata).

Wild and weedy vegetables

· Nyevhe (ulede) (Cleome gynandra)
· Musemwasemwa (Cleome monophylla)
· Musungusungu (umsobo) (Solanum nigrum)
· Derere (idelele) (Corchorus asplenifolius).

· Bidens pilosa
· Amaranthus spp.
· Commelina africana
· Galinsoga sp.

Status of research on traditional indigenous vegetable crops

Research on traditional vegetables has recently started at the Horticultural Research Centre (HRC) and the University of Zimbabwe. At HRC Brassica juncea, one of the most popular cultivated vegetables, was initially selected as a priority. When seed of the vegetable was procured from seed companies for trials, the plants flowered too soon before harvesting. A landrace was therefore obtained from local people, one known to flower late and with bigger leaves. This variety has been selected since 1990. This year the seed will be passed on to a seed company for multiplication and distribution to farmers.

Fertilizer and spacing trials have been carried out on Cleome gynandra. Because this is one of the most popular of the wild/weedy traditional vegetables, and is often sold in urban areas during the rainy season, it has been targeted for improvement from the first trials that were carried out. Variation was observed in plant morphology and in the colouration of stems and leaf stalks (green or purple). Germination and growth rate also varied, and there was a response to inorganic fertilizer application of both yield and growth rate. An improved variety from Tanzania also showed lack of uniformity in germination and growth rate. Genetic improvement by selection will be necessary before agronomic trials. The objective is to bring Cleome into domestication to be able to produce and sell it in the off-season.

Other species that have been collected and are being multiplied for improvement are: Solanum nigrum, Brassica carinata, Corchorus spp., Cleome monophylla and pumpkin. Collecting germplasm of traditional indigenous vegetable species will be one of the first priorities of the National Plant Genetic Resources Centre once staff and the storage facilities are in place in 1996. As a first step, a countrywide survey will be conducted through the Department of Technical and Extension Services to gather baseline information on use and production of traditional vegetables (Mapfumo, pers. comm.).

Reference

Nyamapfene, K. 1991. Soils of Zimbabwe. Nehanda Publishers, Harare.