Lecture 9. Salad and leaf vegetables

Summary

The leaves of many herbs, shrubs, trees and vines are eaten either raw in salads or as cooked greens. These leafy vegetables provide important sources of vitamins, minerals and fibre, just as other vegetables. While species of many diverse families provide salads and edible greens, three play a particularly important role: Brassicaceae, Asteraceae, and Chenopodiaceae. Some leafy vegetables are from families (Amarathaceae and Chenopodiaceae) that are the source of important pseudo-cereals, grain crops that, after decreasing in importance for a time, are now experiencing a resurgence of popularity.

Examples:

• Brassicaeae, also called Cruciferae, is a large family of 390 genera and 3000 species that are annual to perennial herbs (rarely shrubby) with mustard oil glucosides. The dry-dehiscent fruits show a great diversity in shape and size, which helps distinguish between genera. The family has a cosmopolitan distribution, but is especially common in open, dry habitats of temperate zones, and is particularly diverse from the Mediterranean to Central Asia, and western North America. Crucifers are not common in the Southern Hemisphere, and there are very few tropical species. The family’s economic importance comes primarily from species that provide salad greens, other vegetables, oilseeds and ornamentals. The salad greens come from diverse genera, including rocket (Eruca sativa) from the Mediterranean, watercress (Nasturtium officinale and others) from central and southern Europe to western Asia, white mustard (Sinapsis alba) and others. The genus Brassica provides most of the leafy and other vegetables. Brassica oleracea, a native of the Mediterranean region and south-western Europe, has been bred to produce many different leafy vegetables, including cabbage, kale, collards (and also broccoli, cauliflower kohlrabi and many other vegetables). Some Oriental leafy vegetables in the Brassica genus have become popular in western countries: Pak-choi (B. chinensis) and pe-tsai (B. pekinensis) – also called Chinese cabbage – and Chinese kale (Brassica alboglabra).

• Asteraceae, also called Compositae is a very large family of over 1300 genera and 21000 species. Evergreen shrubs and perennial rhizomatous herbs are most typical of the family, but tap-rooted and tuberous-rooted perennial, biennial and annual herbs are also common. Vines and large trees are infrequent. Leaves are alternate (or rarely opposite), simple (rarely compound), and usually lobed or toothed. The characteristic inflorescence is headlike (known as a capitulum), composed of numerous small individual flowers (called florets), protected by protective bracts (the involucre). The entire inflorescence looks like to a ‘flower’ to laymen. Cosmopolitan (with the exception of Antartica), composites are particularly well represented in the semiarid regions of the tropics and subtropics, and are poorly represented in tropical rainforests. The economic uses are as diverse as the family: food plants (lettuce, artichokes, sunflowers), ornamentals, insecticides and medicines. The most important food of commercial importance is lettuce (Lactuca sativa), probably the most popular salad plant in the world. Domesticated in Asia Minor or the Middle East from the wild species L. serriola, it is now cultivated in temperate, subtropical and tropical lands. Endives (Cichorium endivia), probably domesticated in the eastern Mediterranean, and are now grown throughout the world. Both endives and lettuce were known to the Egyptians, and were cultivated by the Greeks and Romans. There are several important non-leafy vegetable in the Asteraceae, including globe artichokes (Cynara scolymus) and Jerusalem artichokes (Helianthus tuberosus).

• Chenopodiaceae is a medium-sized family with about 100 genera and 1500 species, widely distributed in temperate and subtropical saline habitats. They are herbs with deep penetrating roots, adapted to obtaining water in arid and saline areas. The leaves are alternate and without stipules, often small, mealy textured or hairy, lobed or spiny. The flowers are inconspicuous, regular, bisexual and arranged in spikelike or cymose inflorescences. The fruit is a small round nut or achene. The chenopods are of commercial importance particularly because of beets, a source of sugar, and because of several vegetables. Beet greens and Swiss chard are different varieties of leafy vegetables derived from Beta vulgaris, a species better known as the source of sugar beets and deep-red beetroot. Spinach refers to the leaves of Spinacia oleracea, which was domesticated in Iran and neighboring areas and spread to China about 600 AD, and from there to Korea and Japan in the 14th to17th centuries. The Arabs introduced it into Spain in the 11^th century, but it did not become widely cultivated until the 18th century. Orache (Atriplex hortensis) is a native of western Asia and southeastern Europe; widely grown until the 18th century, it has decreased in popularity since. Chenopodium quinoa is grown for its edible leaves and seeds in the Peruvian Andes, its seeds are an increasingly popular pseudo-grain. It was domesticated in the Andes 3000 to 5000 years ago.

• Other families that give leafy vegetables:

• • Aizoaceae (Tetragonia)
  • Amaranthaceae (Amaranthus)

References:

Chweya, J.A. and P.B. Eyzaguirre, editors. 1999. The biodiversity of traditional leafy green vegetables. Rome, International Plant Genetic Resources Institute.

Fleuret, A. 1979. Methods for evaluation of the role of fruits and wild greens in the Shamba diet: a case study. Medical Anthropology 3:249-269.

Getahun, A. 1974. The role of wild plants in the native diet in Ethiopia. Agro-ecosystems 1:45-56.

Mapes, C., F. Basutto and R. Bye. 1997. Ethnobotany of quintonil: knowledge, use and management of edible greens Amaranthus spp. (Amaranthaceae) in the Sierra Norte de Puebla. Economic Botany 51:293-306.

Questions for discussion:

• Is the custom of eating raw leafy greens restricted to certain regions of the world?
• Are leafy greens – raw and cooked – considered vegetables of low prestige or high prestige where you grew up?
• What role do leafy greens play in human nutrition?

Perspective for discussion:

"Nutritional and local development programmes can produce public awareness materials including recipes, cultural histories of the species, lists of local names for these foods, simple agronomic guides on production including intercropping arrangements and how to maximize production from small patches. In general, there are many misconceptions about traditional leafy vegetables that have arisen with the cultural and economic changes of modernization and globalization. As a result they still have a low status in many parts of Africa. Armed with a better understanding of the diversity and potential of leafy vegetables … local African institutions and research programmes will be empowered to preserve and deploy African leafy vegetable genetic resources for the development of the continent’s farmers and consumers."

From: Chweya, J.A. and P.B. Eyzaguirre, editors. 1999. The biodiversity of traditional leafy green vegetables.

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