Edamame (pronounced “eh-dah-MAH-may”) is a specialty vegetable soybean that originated in China more than 2000 years ago. Today it is known as a traditional Japanese vegetable (Jian 1984). Edamame is a Japanese word which translates to English as “branched bean”. In Chinese, this vegetable is called mao dou and its English translation is “hairy bean”. In the U.S., this crop is most commonly referred to as edamame but is sometimes called vegetable soybean or sweet bean.
In the U.S., edamame is sold as either whole pods or shelled beans. Only edamame beans are eaten and the pods are discarded. Shelled edamame can substitute for green peas or lima beans in any recipe. In China, shelled edamame beans are stir-fried with other ingredients. In Japan, pods are boiled in salted water, beans are squeezed directly from the pod into the mouth, and the pods are discarded (Konovsky et al. 1994).
In addition to having a sweet, nutty flavor, smooth texture, and good digestibility, edamame are also nutritious (Rackis 1978). Edamame contains about 38% protein. One-half cup serving contributes 11 grams of protein towards the average daily adult requirement of 46–56 grams (USDA 2005; Alleman et al. 1999). Edamame is also rich in calcium, vitamin A, and phytoestrogens (plant-produced estrogens).
Botanically, edamame is the same species as grain or field soybean (Glycine max (L.) Merrill). However, edamame has traditionally been selected for its large seed size, sweet flavor, and high levels of digestibility over field soybean.
Like other legumes, edamame can fix nitrogen (N) to meet its N fertility needs. In addition, there can be residual nitrogen left in residues after harvest. Thus, edamame can offset nitrogen fertility needs of the following crop, thereby improving the economy of cropping systems. The purpose of this publication is to describe how to grow, market, and use edamame.
Edamame plants grow to a similar size as bush green bean plants (Figure 1) and are easy to grow in the Pacific Northwest. Choosing the right cultivar and paying particular attention to planting needs are the keys to success with this crop.
One of the most critical steps to success in growing edamame is choosing a cultivar that will mature in your area. Another consideration is the cost of edamame seed. Seed costs range from $10–$40 per half pound, depending on the cultivar and source.
All edamame, except the earliest maturing cultivars, are considered “short-day” plants (Shanmugasundaram 1981). The terms “short-day” and “long-day” refer to photoperiod, or the daily amount of light and darkness. Short-day plants switch from plant growth to flower production when nights are long. Cultivars that do not flower by mid-July may not produce pods before the end of the growing season. Since the Pacific Northwest has long summer days and short nights, combined with relatively cool summer temperatures, growers here must choose a cultivar that is less sensitive to photoperiod and matures early.
Like all soybeans, edamame is ranked in maturity groups, from 000 to X. The 000 group has the earliest maturation, and cultivars in the X group mature the latest (Williams et al. 2012; Weibold 2014). Growers in the Pacific Northwest should choose cultivars in the 000–3 maturity groups. While cultivars in these early maturity groups will be listed as maturing in 70–90 days, in the Pacific Northwest, they will take 100–120 days to mature. Refer to Table 1 for a list of varieties that have been tested in Washington state. Compare days to maturity in this table to the number of days provided by seed catalog as a guide to determine the number of days to maturity for other varieties.