Overstory #12 - Perennial Leaf Vegetables
Summary: There are numerous tropical perennial trees and shrubs with highly nutritious edible leaves. Such plants can form the foundation of a highly productive, low maintenance garden.
Most modern gardens have tended to focus on just a very few leafy edible species, the majority of which are short-lived annuals like lettuce, cabbage, and common spinach. Many of these are temperate species, which are poorly adapted to hot, humid conditions and require special tending and frequent replanting. Adding lesser-known tropical perennials to the garden contributes to diversity in the ecosystem and in the diet, while cutting down on the work to produce abundant quantities of nutritious leafy greens.
Apart from being ornamental and edible, many perennial vegetables can be grown on the edge of tree plantings, such as along paths. They can serve other functions around the house such as view screens (Pacific spinach, moringa), ground covers (sweet potato, bitter melon), and edge plants as a barrier to weeds (sissoo spinach, garlic chives). Many of these plants have medicinal as well as culinary utility.
Harvesting Perennial Vegetables
For most perennial vegetables, the best part to eat is the tender growing shoot or tip which includes the young leaves which have not yet matured and the soft growing stem. Shoots are favored for eating because they are sweeter and more tender than older growth. The mature leaves can often also be eaten, but require longer cooking times and can still be tough eating. The way to harvest shoots is to simply snap off the tender stem where it naturally breaks, leaving behind the more mature and fibrous stem and leaves. The plant then regrows more stems, and production of shoots is multiplied! If the plants receive sufficient water, growth of new shoots continues throughout the year in subtropical and tropical climates, and throughout the growing season in temperate climates.
Adding Perennial Vegetables to the Diet
Most plants have nutritive as well as non-nutritive effects on the body. In other words, eating too much of one thing can have toxic effects or upset digestion. The toxic effects can be moderated by including small amounts of a wide variety of leafy vegetables in the diet. For most plants, about 10 shoots, a handful (1/2 cup cooked), is a good amount per person for one meal.
Some Cooking Usually Required
Plants from the tropics have evolved even more toxins as a defense against predators than those from temperate climates. For example, the leaves of Tahitian taro (and other taro species) contain calcium oxylate crystals that are highly irritating to mouth and throat. Cassava leaves often contain substances which can release highly toxic hydrocyanic acid. That is why many plants of sub-tropical or tropical origin require cooking in order to eat them. Cooking dispels or denatures the harmful toxins, and makes the remaining portion safe to eat. Because much of the nutrients and enzymes are destroyed in the cooking process, it is best to cook for the shortest time possible while still removing toxic effects. References such as Bailey (1992, see reference below) give recommendations for cooking times and methods for many popular subtropical/tropical perennial vegetables.
Knowledge of edibility of plants has been developed slowly over a long period of time. Experts in the edible plants recommend strongly against testing an unknown plant yourself for edibility. Such trials can be toxic to the system and/or fatal. There are some excellent reference books available (see list below).
There are a surprising number of perennial vegetables available which have been selected for their vigorous growth, favorable taste, lower content of bad tasting or toxic substances, and beauty. Once established, plantings of perennial vegetables can provide an abundance of leafy vegetables for years.
Some Examples of Promising Tropical Vegetable Species
- katuk (Sauropis androgynus) leaf tips
- sweet potato (Ipomoea batatas) leaf tips, tuber
- cassava (Manihot esculenta) leaves, root
- Pacific spinach (Abelmoschus esculentus) leaf tips
- Tahitian taro (Xanthosoma braziliense) leaves
- chaya (Cnidoscolus chayamansa) leaf tips
- Okinawan spinach (Gynura crepioides) leaf tips
- Ceylon spinach (Basella rubra) leaf tips
- Sissoo spinach (Alternanthera sissoo) leaf tips, leaves
- moringa (Moringa oleifera or Moringa stenopetala) leaf tips, leaves
For an expanded list of Perennial Leaf Vegetables and further information, download (pdf format), Leaves to Live By...Perennial Leaf Vegetables.
Martin, Franklin W. and , Ruth M. Ruberté. 1979. Edible Leaves of the Tropics. Antillian College Press, Mayagüez, Puerto Rico. Perhaps to be reprinted by ECHO, 17430 Durrance Road, N. Ft. Meyers, FL 33917-2239, Fax: (941) 543-5317
Facciola, Stephen. 1990. Cornucopia: A Source Book of Edible Plants, Kampong Publications, Vista, California.
International Institute of Rural Reconstruction. 1993. The Bio-Intensive Approach to Small-Scale Household Food Production, IIRR, Room 1270, 475 Riverside Dr., New York, NY 10115
Martin, Franklin W.. 1994. Plants for Use in Permaculture in the Tropics, Yankee Permaculture, P.O. Box 672, Dahlonega, GA 30533-0672
ADAP Project, Pacific Islands Farm Manual. 1994. ADAP Project, Tropical Energy House, University of Hawaii, Honolulu, HI 96822
Bailey, John M. 1992. The Leaves We Eat, South Pacific Commission, B.P. D5, Noumea Cedex, New Caledonia
About the Authors
Craig R. Elevitch is an agroforestry specialist with more than ten years of public and private sector experience in tropical agroforest and forest management.
Kim M. Wilkinson is the Education Director for Permanent Agriculture Resources and editor of The Overstory. She has B.A. degrees in Anthropology and Ecology from Emory University.
Related Editions to The Overstory
- The Overstory #64--Homegardens
- The Overstory #54--The Agroforester's Library Part Two-Species References
- The Overstory #26--Fast Food (Part 2 of 2)
- The Overstory #16--Multipurpose Trees
- The Overstory #3--Weeds as a Resource