How to grow soybeans (edamame)

These beans have been grown and used for cooking for thousands of years in South-east Asia and are becoming increasingly popular in UK kitchens, too. High in protein, they can be steamed or boiled in their pods and added to dips, salads, side dishes, stews or casseroles.

Soybean plants are frost-tender and need a long hot summer to crop well, so they are only suited to being grown outdoors in milder regions of the UK. Note this bean contains toxins and must be cooked before eating and shouldn’t be eaten raw.

How to grow soybeans

Grow soybeans from seed sown from mid spring to early summer, either starting seed indoors in pots or sowing directly where plants are to grow from late spring. Grow in a sunny sheltered site on good soil and keep watered so the soil doesn’t dry out. Harvest from late summer into autumn. Compost the plants at the end of the season.

Growing soybeans: jump links

• Sowing soybeans
• Caring for soybeans
• Harvesting soybeans
• Growing soybean: problem-solving
• Buying soybeans

Where to grow soybeans

This type of bean needs to be grown in warm areas and in full sun, on soil that is fertile and moisture retentive. Plants grow up to 1.2m high and are best grown in a site sheltered from wind.

Sowing soybeans indoors

From mid to late spring, sow seeds 5cm deep into individual 8cm pots or deep root trainer pots filled with moist potting compost. Place in a propagator, or cover with polythene and stand in a warm place, at a temperature of around 20°C. Once seedlings appear, move to a well-lit windowsill or a heated greenhouse and ensure the compost stays evenly moist. Harden off the seedlings to gradually acclimatise to the outdoors before planting out when all danger of frost is past. If cool weather delays planting out and seedlings have filled their pots with roots, transplant into larger (13cm) pots.

Sowing soybeans outdoors

Ideally, warm the soil before sowing seed direct, by placing cloches, fleece, or clear polythene over the ground for at least a couple of weeks. Sow from late spring to mid-summer, placing 2-3 seeds together, 5cm deep and 15cm apart, in rows 45cm apart. Once the seedlings have emerged, thin if necessary to leave one seedling, selecting the strongest and healthiest one to remain. If space permits, make several sowings over a couple of months so you can harvest over a long period.

Caring for soybeans

A regular supply of water is essential for pod and fruit-producing crops like edamame/soybean. During dry conditions, water thoroughly 2-3 times a week. Mulching the soil around the roots with well-rotted compost helps the soil retain moisture. Weed regularly as weeds would compete with the beans for water and nutrients.

Harvesting soybeans

Soybeans are ready to harvest around 12 weeks after sowing, in late summer or autumn. For edamame beans, pick when the pods are green with the shape of the beans is visible inside. Either shell the beans from the pods before cooking or cook the pods whole and pop the beans out afterwards. For soybeans, allow the pods to develop to produce large beans, then dry thoroughly in an airy spot under cover and shell beans from the pods before storing.

Growing soybeans: problem solving

Poor growth is commonly caused by low temperatures, so avoid sowing too early and protect young plants with fleece or cloches.

Small pods and beans are likely to be caused by lack of water. Ensure the crop is watered regularly during dry spells, and spread an organic mulch such as garden compost or chipped bark, to hold moisture in the soil.

Slugs and snails can damage the seedlings, which are particularly susceptible when emerging from the soil. Surround the seedlings with a physical barrier, such as collars made from plastic bottles, protects them at this most vulnerable stage. Apply a wildlife-friendly slug and snail killer or a proprietary barrier.