How can I garden in the hot humid tropics?
Letters from EDN readers often contain questions similar to this. Even experienced gardeners can get discouraged when they move to the humid tropics from a temperate country and plant the vegetables they know from home. Others of you have not had gardening experience in any climate, but now face the need to learn quickly. The approach of the two books described below is so different that they complement each other very well.
The best way to begin gardening in hot humid regions is to try those plants that God has clearly made for such climates. However, temperate crops are often in demand because of the increased variety that they add to the diet and their value as a cash crop to replace imported vegetables. Techniques and Plants for the Tropical Subsistence Farm is oriented toward plants that are adapted to the tropics. Growing Vegetables in Fiji is more oriented toward growing temperate vegetables, with some discussion of other vegetables.
Dr. Frank Martin and Ruth Ruberté with the USDA's Tropical Agriculture Research Station in Puerto Rico wrote a 56-page book called Techniques and Plants for the Tropical Subsistence Farm. (It is now out of print, but ECHO sells a photocopied version in a binder for $5 plus postage.) It is an excellent introduction to a wide variety of foods that are adapted to hot, humid regions. Its scope is a bit broader than only gardening, as the title implies. The table of contents lists: overall planning; vegetables and cereals (leaves, legumes, roots and tubers, fruit vegetables, cereals); trees (fruit trees, vegetable trees, leguminous trees, trees for wood); forage crops (site selection & preparation, planting, management, grazing, storage, selecting forages, grasses, legumes, misc. forages). Their approach to insect control is less specific with an emphasis on organic methods. (It is quite likely that insect control is less of a problem with the native tropical plants.) Here are some excerpts.
"Phosphorous is an essential, limiting element in tropical soils as often as nitrogen. It is important in stimulating root development and is necessary for fruit and seed development. Although it is common enough in the soil, most of it is insoluble, unavailable for plant use. Manure, compost and cover crops do not add enough phosphorous to the soil" and tend to become insoluble when they are added. He then discusses deficiency symptoms. Commercial fertilizers are one source. "Bonemeal is a useful additive though much of its phosphorous is insoluble. Marine organic materials (seaweeds, fish) are other good sources. There does not seem to be an easy solution to the problem, but a soil with adequate humus and good aeration slowly releases soluble phosphates from the insoluble forms."
"Indian or tropical lettuce (Lactuca indica) from Southeast Asia is considered by some to be the best lettuce for the hot humid tropics. Like all lettuces, it requires a fertile soil. Seeds are small and seedlings require careful attention. [Ed: So many plants come up wild we no longer need to replant, however.] The plants grow rapidly and produce large succulent leaves. These may be harvested individually, or the tops may be snapped off... [to be] replaced rapidly by new growth. Once flowering begins, it cannot be suppressed, but leaves may be harvested until exhausted. Year-round production is easily achieved by planting every 3-4 months. Yields are excellent and the plants can be grown in pots. The lettuce is somewhat bitter in taste, but its flavor and texture are perfect for mixed salads." [Ed: It is also excellent as a cooked green. ECHO has seed.]
Kirk Dahlgren worked as the Rural Development Director for the Peace Corps in Fiji. He wrote a 123-page book for the Peace Corps called Growing Vegetables in Fiji. This book is an excellent general introduction to gardening in the tropics (or elsewhere for that matter). We think so much of the book that we have reprinted it (US$5 plus postage). As mentioned earlier, a special emphasis is placed on growing temperate vegetables. The climate is hot and humid in much of the country, similar to conditions faced by many of you. His writing is clear and choice of subjects excellent. He has an unusual ability to get right to the most important points and to explain them clearly in as few words as possible. The table of contents lists: the Fiji vegetable crop environment; building and maintaining soils; cultural methods of vegetables; the garden crops of Fiji; growing vegetables under plastic; composting and mulching. Some examples follow.
"The culture of many of these new crops required the learning of a totally foreign propagation method-the use of seeds." Traditional Fijian crops are propagated vegetatively, i.e. a piece of the plant other than a seed is used to produce new plants. "The vegetable crops the missionaries brought evolved in temperate zones where plants needed to produce resistant bodies, i.e. seeds, to survive the harsh winters." Crops the Indians brought had a similar need to survive dry months. Because in Fiji the weather is always just right for the plants to grow, it is often advantageous for plants to reproduce through means other than seeds.
Here is an excerpt from the discussion of carrots. "Fiji relies largely on carrot imports to satisfy local demand. Carrots do well in Fiji, however. ...Carrots are small-seeded, slow-germinating, and slow to establish so require a steady supply of moisture and a high measure of weed control. Quick growth produces better carrots. Carrots are high in vitamin A and have good keeping qualities." He then gives recommended varieties and detailed cultural procedures. "Show extra attention to weed control. Weeds in carrots can be controlled by spraying with kerosene at the three-true-leaf stage. The rate is 450 liters/ha (45 ml/square meter). Spray on a sunny day for best control." Diseases, pests and their control [usually chemical rather than organic] are discussed for each vegetable. He lists three common problems: cavities caused by calcium deficiency, galls caused by nematodes, and split root tips caused by excess soil nitrogen.
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