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Edamame: The New Garden-Type Soybean

Quick Link to edamame seed sources

Due to high nutritional value and health benefits, soy foods are gaining considerable interest in the market place. Much of this interest has focused on soybean products such as tofu, soy milk, soy-protein fortified flour, or meat analogs constructed from extracted soy protein. Interestingly, soybeans are also an excellent vegetable and may be eaten directly from the pods similar to other beans or peas. When presented in this fashion, the soybean is called vegetable soybean or edamame.

Growing Edamame

Edamame is very easy to grow—as easy as growing any bush bean. It’s planted the same way as bush beans, and a mature soybean plant (edamame plant) is about 2-feet tall. After the soil has warmed to 65°F, sow seeds 1 inch deep and 2 or so inches apart, in rows 15-30" apart. Don’t rush planting. If the soil isn’t warm enough, the seed will not germinate. Stagger the planting times to provide a continuous harvest that will not overburden your gardening time with picking and storing beans.

Harvesting Edamame

The best way to harvest edamame is to manually pick the immature, green pods. This can be accomplished by hand picking each pod, or you can cut the plant at the base or pull the whole plant out of the ground and pick pods by hand. The vegetable (botanically, it is a fruit that is classified by type as a legume) is ready to harvest after the seeds have reached full size but before any pod yellowing begins. Harvesting edamame at the right time is critical for maximum texture and flavor. If pods are allowed to turn yellow much of the quality is lost. The quality is best when the pod is plump and bright green, similar to snow peas in color.

Cooking and Storing Edamame

Boil or steam the pods for 4 to 5 minutes (in lightly salted water if your taste prefers), cool under running water, and squeeze the seeds from the pods. Beans are difficult to remove from pods unless blanched or steamed. The soybeans can be eaten by themselves as a “finger food” or added to soups, salads, fried rice, or other dishes. Do not eat the shells, as they are too fibrous to be edible.

After cooking, the beans can be frozen in or out of the pods and enjoyed later as an out-of season treat. Store in freezer (-20 degrees Fahrenheit). The advantage of eating the immature, green soybeans instead of the ripened, dried seeds is the better taste, crunchy texture, and appealing green appearance. They taste good cold or hot, and the attractive bright green color enhances the appearance of many dishes. Additionally, the young, green soybeans are more easily digested since the complex carbohydrates (oligosaccharides) of the mature seeds are not yet formed.

Edamame Varieties Available

Although all soybeans are edible, certain soybean varieties with larger seeds and milder taste have been developed for human food usage and are commonly sold in Japan and Korea. These Asian food varieties have desirable characteristics but are not well adapted to the climate, insects, and diseases of the United States. Soybean breeders in the United States have crossed some of these large-seeded Asian varieties with adapted US grain varieties and developed varieties that are better adapted vegetable types for growing in the United States.

The garden type or vegetable soybeans have an optimum harvest period for green pods of just a few days since all the pods on a soybean plant tend to develop together. The advantage of growing several varieties with different maturity dates is longer harvest periods that are spread out to allow several harvest sessions. This may also be accomplished by having several planting dates (estimate 3 days delay in planting for one day delay in harvest but this will vary widely). Like all soybeans these varieties are self-pollinating and true-breeding, and therefore you may let a few plants ripen without picking and use these seeds for next year’s planting.

Commercial edamame suppliers:

Johnny's Selected Seeds
ParkSeed Company
Vermont Bean Seed Company

University of Illinois: GardenSoy variety samples available
At the University of Illinois, selections have been made from specially bred hybrid populations of large-seeded soybeans and now there are a number of promising vegetable-type soybean lines adapted to Illinois growing conditions.Thirteen varieties, named with the prefix Gardensoy, have been released ranging from early maturing (maturity group 0) to late (group IV). The varieties produce soybeans that range from about 50% more to twice as large as the common grain types of soybean grown in Illinois. The tradeoff is lower yield. These vegetable types yield only about 60 to 80% as well as grain types of soybean and therefore are not competitive for large-scale production or processing. Because of their bigger seed size and better taste they are being offered to home gardeners for small scale production and hand harvest. As harvest machinery and techniques are developed for proper harvest of the vegetable types of soybean, larger scale commercial production may become practical.

The University of Illinois has ongoing research plots of edamame each year. For additional information on research trials and/or sample seed packets that may be available for a small fee, contact Research Specialist Theresa Herman.

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