The most edible species have been recorded in the woody genera Acacia (10), Albizzia (8), Bauhinia (9), Erythrina (8), Leucaena (7), and Pterocarpus (8), the herbaceous genera Lathyrus (7), Trifolium (18), Trigonella (9,) Vicia (16), and Vigna (10), and in five genera with both woody and herbaceous species: Cassia (22), Crotalaria (15), Desmodium (7), Lespedeza (7), and Sesbania (6). A list of legume species with edible leaves is summarized in Table 1.
Fennugreek (Trigonella foenum-graecum L.) is an important potherb in southern Asia where it is known in Hindi as mehti. Leaves are also eaten in the Mid East and Mediterranean, Kenya, Tanzania, and Malawi.
Leaves or tender stem tips of the common pea (Pisum sativum L.) are eaten in both tropical and temperate regions, in Malawi Burma, Indonesia, China, and Japan, but it does not appear to be a major vegetable anywhere. Edible leaves were widely promoted as one of many advantages of the winged bean [Psophocarpus tetragonolobus (L.) D.C.], recorded from four countries in southern Asia (Bittenbender et al. 1984), but in practice they are not often eaten. Peanut (Arachis hypogaea L.) is a widespread but obscure leaf vegetable, reported from Brazil, Paraguay, Argentina, Senegal, Mali, and Indonesia.
The genus Cassia includes 22 trees, shrubs, and herbs used as leaf vegetables. Sicklepod (Cassia tora L.), a weedy herb widely distributed in the tropics and subtropics, is eaten in Mali Cameroon, Tanzania, India, and Indonesia (Bittenbender et al. 1984). It is also noted as a wild edible plant in the southeastern U.S. (Peterson 1978). Young leaves of Cassia obtusifolia L. are eaten in South America and India (Bittenbender et al. 1984). In northern Senegal this herb grows abundantly during the rainy season and its leaves are consumed in great quantity as most other foods are scarce at that time. Then it provides the major source of vitamins A and C, usually being added to millet porridge (Becker 1983).
Leucaena leucocephala (Lam.) de Wit (often called L. glauca (L.) Benth.) and Sesbania grandiflora Pers. are rapid-growing nitrogen fixing trees widely naturalized in the tropics and planted for many uses, especially fuel soil conservation, fodder, and poles. Leucaena leaves are eaten in Central Africa, Thailand, the Philippines, Indonesia, and its native Mexico. Young Sesbania leaves are eaten in Attica, Pakistan India, Bangladesh, Thailand, Malaysia, Indonesia, New Guinea, the Pacific, and also in Guyana.
Witrock and Witrock (1942) in an article entitled "Food plants of the Indians" state, "Species of clover, Trifolium, were foraged by California tribes. Indians were often observed in the fields eating the plants raw, though they did have a pouch of salt from which they would occasionally take a pinch to give a bit of favorand incidentally aid digestion." This statement has been paraphrased in many edible wild plant guides for various parts of North America, which are similarly vague as to which species were eaten. Many of these "Wild" legumes are actually forage crops escaped from cultivation, such as alfalfa (Medicago sativa L.), clovers, vetches (Vicia), and sweet clovers (Melilotus).
In many tropical regions gathered wild vegetables are very important in the diets of rural people, especially seasonally (Becker 1983, Okigbo 1977, Villareal and Opena 1976). Many are marketed, providing cash income to the harvester and relatively inexpensive vegetables to the public (Bittenbender et al. 1984, Villareal and Opena 1976).
Where environmental degradation is accelerating, germplasm collections of wild food plants should be made before potentially valuable traits are lost. The little-known fruits and vegetables grown for home consumption in the tropics, including many legumes, represent another vast reservoir of potential crop species for other regions.
The cowpea has been well documented as a multi-purpose legume crop, especially in eastern and southern Africa. For a crop of leaves, cowpeas are sown thickly and the entire plants harvested at three weeks. Seeds may be broadcast alone or into a grain field, and thinned gradually with the thinnings cooked. Some indeterminate cultivars are suitable for harvesting leaves, young pods, and mature seeds, each over a long period, and for feeding the residues to livestock. If seeds are desired, leaf harvesting should cease before the pods begin to expand. In Botswana, researchers have selected triple-purpose landraces for seed, forage, and leaf vegetable production. In Zimbabwe, the leaf and seed are given equal importance, while in the more humid parts of East Africa, cowpeas are grown mainly for leaves (Barrett 1987).
The timing of the leaf removal has a great effect on a planes ability to recover from defoliation. In bean and cowpea, removing too many young leaves at once will impair seed yield, while removing the oldest leaves has increased it (Barrett 1987).
In a trial with six diverse African cowpea cultivars, removing all young leaves down to the fourth fully expanded leaf from the apex reduced seed yield, but raised the combined dry weight of seeds and leaves by 18% on the average, and up to 48% for one cultivar. Gradual harvesting of young but fully expanded leaves raised the combined dry weight by up to 109%; the average increase was 36% (Barrett 1987).
Most domesticated legumes are valued primarily for seeds, yet the leaves of many grain legumes equal or exceed the protein content of their seeds on a dry weight basis. Because leaves are produced earlier and in much greater volume than seeds, the protein productivity is higher-about 15 times better for cowpea and 3.4 times better for winged bean (Bittenbender et al. 1984).
Edible woody species are often planted in hedges around homes, and trimmed for a constant supply of greens (Morton 1968). In Nigeria, Pterocarpus species and other trees produce flushes of new edible leaves in the dry season when annual vegetables are scarce. Flushing can be stimulated by timely pruning (Okigbo 1977).
Very few legume leaves are recorded as being eaten raw or in salads, where the details of preparation are not known, the leaves should be boiled, and the cooking water thrown out. This will either deactivate the toxins or dilute them to safe levels. Martin and Ruberte (1975) give sound advice on how to prevent poisoning.
Some of the "edible" species remain hazardous even after cooking, and are only consumed when facing starvation, but most are safe when prepared properly. Future research should distinguish between famine foods and gathered vegetables, and evaluate methods of preparation.
Since chemical pesticides do not normally leave residues in the seeds, many are certified as safe for use on legume crops. However, safety on edible leaves is unknown and present pesticides are not labeled on these crops when used as leaf vegetables. The hazard to peasant farmers in the tropics should be addressed.
Almost all species are cooked in some way This improves quality by removing toxins and softening the texture. In Kenya, it is common to boil vegetables with trona, a crude hydrated sodium carbonate. Trona softens and improves the flavor of vegetables, but it reduces the vitamin C content (Bittenbender et al. 1984).
In at least 11 tropical African countries cowpea leaves are dried to store them for the dry season. Usually they are first steamed or boded, but not in all places. Sun-drying requires one to three days; storage for up to a year is possible since dried cooked leaves are not damaged as much by insects as dried seeds. Excessive losses of P-carotene, vitamin C, and the amino acid lysine often occur in sun-dried leaves, but can be reduced by minimal cooking followed by drying in the shade (Barrett 1987). Bean leaves are dried in at least five African countries, and a few other legume leaves are also stored dry (Bittenbender et al. 1984).
Arachis hypogaea L. (peanut)
Lablab purpureus (L.) Sweet (lablab bean)
Phaseolus lunatus L. (lima bean)
P. vulgaris L. (common bean)
Pisum sativum L. (pea)
Psophocarpus tetragonolobus (L.) D.C. (winged bean)
Trigonella foenum-graecum L. (fennugreek)
Vigna unguiculata (L.) Walp. (cowpea)
Cajanus cajan (L.) Millsp.(pigeon pea)
Cicer arietinum L. (chick pea)
Cyamopsis tetragonoloba (L) Taub. (guar)
Glycine max (L.) Merrill (soybean
Kerstingiella geocarpa Harms. (Hausa groundnut)
Phaseolus calcaratus Roxb. (rice bean)
P. coccineus L. (runner bean)
Sphenostylis stenocarpa (Hochst.) ex A. Rich (African yam bean)
Vicia faba L. (fava bean)
Vigna radiate (L.) Wilczek (mung bean)
Voandzeia subterranea Thouars. (bambara groundnut)
Forage crops and wild herbs
Cassia tora L. (sicklepod)
Cassia obtusifolia L. (cassia)
Crotalaria longirostrata Hook. et Am. chipilin)
Desmodium cinerium D.C. (tick trefoil)
Lathyrus sativus L. (grass pea)
Lespedeza bicolor Turcz. (lespedeza)
Medicago sativa L. (alfalfa)
Melilotus alba Medic. (white sweet clover)
Rothia trifoliata Pers. (rothia)
Trifolium pretense L. (red clover)
Trifolium repens L. (white clover)
Trigonella suavissima Lindl. (trigonella)
Vicia sativa L (vetch)
Vigna marina (Burm.) Merr. (vigna)
Acacia nilotica Del. (scented thorn)
Albizzia procera Benth. (albizzia)
Bauhinia malabarica Roxb. (bauhinia)
Cassia siamea Lam. (kassod)
Ceratonia siliqua L. (carob)
Erythrina berteroana Urb. (coral bean)
Gliricidia sepium (Jacq.) Steud. (madre de cacao)
Leucaena leucocephala (Lam.) de Wit. (leucaena)
Pithecellobium dulce (Roxb.) Benth. (Manila tamarind)
Pterocarpus indicus Willd. (narra)
Sesbania grandiflora (L.) Pers. (sesbania)
Tamarindus indica L. (tamarind)
Fig. 1. Number of species with edible leaves in the Fabaceae (Leguminosae) subfamilies.
Fig. 2. The 16 legume genera with the most species of those that contain edible leaves.
Fig. 3. Number of legume species used as leaf vegetables by continent.