The soybean is an erect annual, 12-30 in (30-75 cm) tall. It looks a lot like other bush beans, with leaflets in threes and bilaterally symmetrical (although very small) pea-like purple flowers. The leaves, stems and especially the pods are red-hairy. Pods are held close to the stems and are 2-3 in (5-7.5 cm) long with 2-4 black, yellow, white, or green seeds. There are three main types of soybeans. The yellow seeded types are grown in industrial farms and typically dried and processed into flours, oils, and various fermented products. The black seeded types are usually fermented and made into sauces and fermented black beans. The green and white seeded (or edamame) beans are the most tender and flavorful, and are often used in the shelly stage. New cultivars are constantly being introduced, especially for the more northern climates, and for use in the shelly stage as edamame beans.
The soybean (Glycine max)is one of the world's most widely grown crops. Probably native to China, and domesticated some 5000 years ago, soybeans are arguably the most important food crop for the billions of people in Japan, China, and all of southeast Asia. In the West, soybeans are cultivated mainly for use in processed foods, cooking oil and animal feeds. In recent years, home gardeners have discovered edamame soybeans.
These edemame pods are ready for harvesting.
Soybeans prefer a slightly acidic soil. These are legumes, and obtain their required nitrogen (N) from the atmosphere, so do not fertilize with additional nitrogen. Phosphorus (P) and potassium (K) fertilizers, however, may be helpful. Some authorities suggest inoculating the seeds with a legume bacteria (Rhizobium japonicum), but I have found this is not necessary in my garden, at least. Besides their use as a food source, soybeans also are grown as a cover crop, a green manure crop to be plowed under, and for erosion control. Light: Grow soybeans, as any vegetable, in full sun. Older soybean varieties would flower and fruit only during the long days of early summer, but newer cultivars are less sensitive to day length. Moisture: Water when dry, but don't overwater. Soybeans need regular watering during early growth, less water during flowering and fruiting, and dry conditions during the pod ripening stage. Hardiness: USDA Zones 7-9. Soybeans require a frostfree growing season of 90-120 days, and a hot summer. Most varieties require average daytime temperatures of at least 68-75F (20-24C), or higher. The green seeded or edamame types are the hardiest soybeans, and some of the newer cultivars can be grown where summer daytime temperatures average just 64F (18C). Propagation: Sow seeds 2 in (5 cm) apart after all danger of frost has passed and the soil has warmed.
A field of soybeans awaits harvesting near Columbus, Ohio. Click to download a large version (800x600) of this image.
Soybeans are one of the world's most important staple foods, right up there with wheat and rice, only better. Soybeans have the highest concentration of protein (35% dry weight) of any plant, and soybean protein contains all ten of the "essential" amino acids (those that the human body cannot synthesize and therefore must be consumed). Soybean oil (20% in dry beans) is the most important cooking oil in the world, and was formerly used for lamp and stove fuel as well. Soybean oil is still used to make margarine, salad oils, soaps, paints, plastics, and many other products. Mature, dry soybeans are tough, even after extended cooking; they are bitter tasting; and they are indigestible, passing straight through the digestive system. With few exceptions, soybeans must be processed by fermentation and extraction processes before they can be eaten. In Japan soybeans are made into tofu and miso; fermented black beans in China; tempeh in Indonesia; and soy milk, soy sauce, soy flour, and various oils everywhere. Sprouted soybeans are popular in Asia. Americans (some, at least) have accepted meat substitute products (like veggie burgers) made from highly processed soybeans. Maybe more would if wasn't called "textured vegetable protein."
Edemame awaiting their fate in lightly salted boiling water.
Immature green seeded soybeans, picked in the "shelly" stage, are digestible and they are delicious, prepared and eaten exactly like boiled peanuts.What? Boiled peanuts? Yes! "Bald" peanuts are a popular summertime snack in South Carolina, Georgia, Alabama, northern Florida, Mississippi, Louisiana and Texas. Peanuts are dug while still immature (the shelly stage, called "green" although they are not that color) and boiled in salted water until the shells are soft. The kernels are then squeezed out into the mouth and the soggy shells discarded. Called edamame or eda mame, boiled immature soybeans are very popular in Japan where they are often served with beer. Here in northern Florida, I grow green seeded soybean cultivars specifically developed for edamame. The boiled beans have a sweet, buttery flavor and a smooth, satisfying texture. Trendy Japanese restaurants serve edamame as snack food, and you can find them in the supermarkets, but (surprise!) they can't compare with home grown!
Edamame soybeans are easy to grow and make a great football season snack. Try some on your friends who think they don't like soybeans, tofu, veggie burgers and soy milk. Pick the pods when they are still green, but filled out and plump. Boil 5-10 minutes in salted water; drain and serve. You'll quickly learn how to pinch the kernels out of the pod and pop them directly into your mouth.