Leafy vegetables are among the easiest to obtain in the tropics and are of great importance in the diet. They contain protein, vitamins A and C and B complex, and minerals, especially calcium and iron, but also magnesium and phosphorus. All contain large amounts of dietary fiber and are low in carbohydrates and fat. Dark green leaves are usually more nutritious than lighter or yellowish leaves. Loose leaves are better than leaves in heads. Young leaves are more nutritious and easier to digest than old leaves.
Leaves often contain toxic substances, of which the most common are oxalic acid, nitrates, glycosides of hydrocyanic acid, and alkaloids. Most leaves should be cooked to reduce toxicity. Leaves should be boiled about 20 minutes, and the cooking water should be discarded. A cup of cooked leaves will give the body as much fiber as it needs. It is wise when eating leaves to vary the species used as food. Only the leaves known to be edible raw should be eaten raw. These include moringa, katuk, lettuce, edible hibiscus, and false roselle.
Many tropical leaf vegetables are perennials. They yield a maximum amount of useful food with a minimum amount of labor. Leaf vegetables respond favorably to rich growing conditions, especially lots of nitrogen fertilizer, for this leads to lush, soft growth. But well fertilized vegetables may contain excess nitrates, harmful to babies and other small children.
See A Comparison of Vegetable Leaves
• Amaranth. Amaranthus tricolor. Greenleaf R108-green with white stripes (Rodale). Tigerleaf-green with red stripes (Rodale). Calliloo-Jamaican; productive, prolific; weed potential; less sensitive to day length. Tasty stems. (EDN 3-1, 4-1).
• Bush okra (Jute mallow, Egyptian spinach). Corchorus olitorius. Only leaves and growing tips eaten; must be cooked; fibers used in twine and burlap sacks; likes heat and water, but is tolerant of drought and humidity. (EDN 21-5).
• Chaya. Cnidoscolus chayamansa. Spineless variety; cuttings only; must boil leaves 5 minutes, discard water, repeat. (EDN 18-2).
• False roselle. Hibiscus acetosella. Tangy, deep maroon leaves eaten raw or cooked; flowers blended with lemonade or in teas give a bright purple color.
• Moringa. Moringa oleifera. Leaves, flowers, and young pods edible; young roots blended with vinegar as horseradish; seeds used to purify water. Moringa stenopetala: larger leaves than M. oleifera providing more shade; stockier, bushier, more vigorous tree; leaves have milder taste when eaten rare; more drought-resistant and has bigger seeds; only occasionally available. (EDN 10-1, 11-7, 21-5, 22-6, 32-5, 35-2, 37-4, 42-2, 43-2).
• Indian (tropical) lettuce. Lactuca indica. Prolific, productive; leaves bitter (serve with vinegar or cooked). (EDN 4-5, 8-4). Available fall of 1996 if harvest goes well.
• Malabar Spinach or Ceylon. Basella alba-White stems; climbing vine; tender stems and succulent leaves edible; likes heat and lots of moisture. Basella rubra-Red stems, large leaves, vigorous; suited for humid regions; easy to cultivate; requires trellis. Boil and discard water to prepare.
• Kale (Ethiopian). Brassica carinata. Unlike most kale, will produce seed in the tropics.
• Katuk. Sauropus androgynus. Cuttings in U.S. only; seed availability highly variable; young stem tips eaten.
• Lettuce. Lactuca sativa. Montello (North American), Maioba (Brazilian-high in vitamin A, resists acidic soils) seeds available fall of 1996 if harvest goes well, Anuenue (Hawaiian), and Queensland (Australian)-slower to bolt in hot weather. (EDN 14-3, 34-4, 41-5).
• Quail grass. Celosia argentia. Upright growth, three varieties available: red leaved, green leaved, and cockscomb (var. cristata). Boiled leaves of all three are tasty. Flowers dry nicely. (EDN 8-2).
• Sweet potato. Ipomea batatas. Leaves and shoot tips eaten boiled. SEE DESCRIPTION UNDER 'ROOTS AND TUBERS'.
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