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Garden Edition: Soy Beans (a.k.a. Edamame)

by Linda Coyner

Online and mail-order seeds catalogs are tempting this time of year, but so will be the plants at garden centers and nurseries come spring. My advice is enjoy the pictures and information but resist purchasing something you’ll see in local garden centers in a couple months. Save your orders for the unusual, whether seed or plants.

In the category of unusual, I gambled on Physalis pruinosa or ground cherry from Underwood Nurseries. It’s a native plant that produces small cherry-size fruits in husks that I remember sampling at a farmer’s market in New York. A plant I also considered ordering stevia, the plant whose leaves can as easily sweeten a cup of tea as a batch of cookies, but I was dissuaded when my research indicated that it’s difficult to germinate (but more on stevia in a future column).

The oddity I splurged on this year is green soy beans or edamame [eh-dah-mah-may]. In the year 2000 when edamame was the subject of a question on ABC's Who Wants to Be a Millionaire?, Regis Philbin wasn’t even sure how to pronounce it. At that time only one or two varieties were available and limited in supply. Information about them was also scarce. There were no growing instructions to be found and I had to plant them to find out they were bush beans.

Today, edamame is more mainstream. You’ll find it in grocery stores, specialty markets and health food stores as frozen whole pods, frozen shelled, or and fresh-cooked in their pods. If you’re lucky, you might come across them in an Asian or farmer’s market sold in a bundles of whole plants with leaves, pods, and stems. You can also give them a taste test in some Japanese restaurants as an hors d’oeuvre.

If the name edamame isn’t familiar, you might have heard it called vegetable soybean, beer bean (the Japanese serve them at bars instead of peanuts), edible soybean, fresh green soybean, garden soybean, green soybean, green-mature soybean, green vegetable soybean, immature soybean, large-seeded soybean, or vegetable-type soybean.

Soy products in general are in the news for their desirable nutritional benefits, particularly for women, and edamame is no different. It packs the same nutritional punch but has a natural sweet, buttery flavor and nutty texture. Unlike many soy products, it doesn’t have to be processed or flavored to taste good. After steaming or boiling whole pods in salted water for 5 minutes they’re ready to eat.

Now the fun begins. The idea is to get the beans out of the pods and into your mouth. Some folks put the pod in their mouth and drag it between the teeth., a method that has the advantage of requiring only one hand. Another way is to squeeze the pod between my thumb and forefinger and aim the beans into my mouth (the Japanese preferred method, I’ve read). Or, try holding both ends of the pod and press the pod’s seam against your lips. Then a slight twist propels the beans into your mouth.

According to the American Institute of Cancer Research, the Chinese have eaten these green soybeans since the 3rd century A.D. They call them mao dao, or 'hair bean,' because of their fuzzy pods. By the 10th century, the Japanese were also eating the beans, which they named edamame, meaning branch beans in Japanese, a reference to how they grow and are harvested.

Basically, edamame or vegetable soybeans are any soybeans harvested in the green-bean stage. The plant comes from the common soybean (Glycine max), and was bred to have the beans eaten fresh. It was also bred for other qualities: large seeds and pods, high percentage of two- and three-seeded pods, dark green pod color, absence of hairiness or dark hairs on the pods and desirable flavor and aroma of cooked pods.

Edamame pods, like all soybeans, are covered with fine pubescence or hairs. Apparently, the color of the hairs is critical to Asian buyers. White or light brown is good; dark brown hairs are bad. Pod blemishes are also not acceptable on the Asian market. Finally, pod color at harvest the best indicator of quality: Pods must be bright green in color with no yellowing.

Growing edamame
There’s more good news: Edamame is very easy to grow—as easy as growing any bush bean. It’s planted the same way as bush beans: After the soil has warmed to 65°F, sow seeds 1 inch deep and 2 or so inches apart, in rows 15-30" feet apart. Don’t rush planting. If the soil isn’t warm enough you won’t get germination. It’s a good idea to stagger planting, so you can have continuous harvests (all pods ripen on a bush at the same time, see below under "Harvesting").

The full-sized plant is similar to bush beans, 2-feet tall or so. I did come across a dwarf one, Early Hakucho, which is only 1 ft. tall, and a tall one, Beer Friend, that grows 2 1/2 to 3 ft.

Northern gardeners will find the growing instructions posted at a Washington State website (http://impact.wsu.edu/reports/specialrpts/edamame.htm) helpful. In an article by Vermont gardener Charlie Nardozzi, edamame took longer than bush beans, with a May planting being harvested in late August.

For poor soils, Nardozzi recommends using a legume inoculate strain for soybeans before planting. (Inoculates help the plants fix atmospheric nitrogen, making the nutrient more available.) He suggests mulching with hay or straw and fertilizing at flowering with a 10-20-20 fertilizer at a rate of 1 pound per 100-foot row.

There aren’t nearly as many commercial cultivars of vegetable soybeans as common grain soybeans, and much less specific information is available about their adaptation.

From what I can glean from published research, there are two types of cultivars, early and late maturing. All but the early-maturing cultivars are photo-period sensitive, which means if they don’t get the right amount of light, they won’t flower. Unfortunately, there is little information on which cultivars are photosensitive.

Until that information becomes available, the best approach to choosing a cultivar is to go for the less fussy early-maturing ones and to seek out seed sources in your growing region.

Here are the cultivars currently available and where to find them:

Agate, 1 1/2 ft, 70-80 days
www.seedsofchange.com

Beer Friend, 2 1/2-3 ft, 75 days
www.territorial-seed.com

Butterbean 90 days
www.johnnyseeds.com

Envy, 75 days
www.johnnyseeds.com; www.Thompson-Morgan.com

White Lion, days to maturity not given;
www.Evergreenseeds.com

Late Giant Black, days to maturity not given;
www.Evergreenseeds.com

Lucky Lion, 70 days
www.Evergreenseeds.com

Green Legend, 75 days
www.Evergreenseeds.com

Early Hakucho,dwarf 1 ft, 65-75 days
www.ParkSeeds.com; www.Evergreenseeds.com

Misono green, 85 days
www.territorial-seed.com

Shironomai, 70 days
www.ParkSeeds.com

Sayamusume, 75 days
www.territorial-seed.com

Maple Arrow, 67 days
www.vermontbean.com

Harvesting
Harvesting edamame at the right time is critical. Beans reach their maximum sweetness about a month after flowering. The quality is best when the pod is plump and bright green, similar to snow peas in color. If they turn yellow, you’re too late. One study reported that a 2-foot-tall plant could yield up to 209 pods. Wow!

All pods on the plants should be harvested at the same time, either by picking pods off individually, or cutting the plant at the base or pulling the whole plant out of the ground.

Happy planting and munching!