Glycine max (90 days) Open-pollinated. In Japan, black-seeded edamame varieties are deemed to have a richer and sweeter flavor than the traditional green or tan-seeded kinds. Tankuro was the winner for productivity and pleasing flavor in our 2010 trial to find the best black-seeded variety. In 2010’s exceptional heat, our May 25 planting produced robust 3' plants loaded with pods packed with an average of 2.4 beans each. They ripened beginning Aug. 17, the same day as Shirofumi. Harvesting would be 1-2 weeks later in a season with average heat units. Pick promptly when the immature seeds are bulging yet the pods are still dark green, before the plants begin to yellow. Those pods that you miss will dry down, maturing beautiful black pearls that can provide your next year’s planting stock. ②
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Average 40 seeds/half oz packet; 160seeds/2oz; 1200 seeds/lb.
Half oz packet sows 10 ft; 1 lb, 320 ft.
Days to maturity are from emergence after direct sowing.
Culture: Edamame are day-length sensitive. Sow around the same time as sweet corn and harvest when most of the pods have expanded but are still green without yellowing. Very sensitive to cold—be sure frost danger has passed, and soil temps have reached 65–80° before seeding. Plant 3–4" apart. Can tolerate dry soil prior to blooming, but needs water during the pod-filling stage. For fresh eating, harvest when most of the pods have expanded but are still green without yellowing. For best flavor harvest in the evening.
Steam or boil the pods for 4–5 minutes, chill quickly for easy shelling. Refrigerate the leftover beans immediately. Fresh-market growers often cut off plants near the base, remove the leaves and bunch into 1 lb units, rather than pick each pod individually.
Good companions: Seedsman Tom Vigue plants edamame in the same furrow as his sweet corn. He thins each to one plant per row foot and suffers little yield loss from either crop: the soybeans are a gift. He sows a living mulch of forage radish that takes off after both main crops are dead. He follows the next year with potatoes which benefit in rotation from all three of these crops.
Saving Seed: Soybean seed is easy to save! To save seed, leave some pods on the plants and wait till stems dry and most of the leaves drop. Expect about 1 lb per 10 row feet.
Pests: Young plants 2nd only to brassica seedlings as woodchucks’ preferred gourmet treat. Japanese beetles also love them but can be controlled by assiduous hand-picking.
Used in China more than 2,200 years ago, then introduced into Japan. The Japanese call them edamame (eh-dah-mah-may), meaning ‘beans on branches,’ and boil and salt them like beer nuts. Edamame are rich in vitamins A, C and E, calcium, phosphorus, protein and dietary fiber. Encouraged by its recent popularity surge, breeders are selecting for larger pods with sweeter beans.
For the latest results of our germination tests, please see the germination page.