Soya Beans

Soya beans, Glycine max, are warm-season legumes originally from South-East Asia. They need full sun, plentiful moisture and a long, hot summer, so they crop most reliably in warmer parts of the UK. Newer, more resilient varieties make them increasingly practical in less favourable districts, but an open cold site will still give disappointing results.

Plants are generally bushy and about 60cm tall, depending on variety. They produce clusters of short, hairy pods, each usually holding two or three small rounded beans. The crop can be harvested at two distinct stages. Plump green immature beans are known as edamame, while fully ripe seeds can be dried for winter dishes.

Soya beans are a useful source of protein and fibre, but they must never be eaten raw. Natural toxins are made safe by thorough cooking. Boil green edamame beans for at least ten minutes before eating, and cook mature beans properly after soaking or preparing them for the chosen recipe.

Choose a variety suited to the UK climate rather than buying seed only for novelty. Soya beans perform best at about 20–30°C, although the tougher recommended cultivars can cope with cooler or less dependable summers. Seed may be labelled either soya bean or edamame bean; the same plants can provide green immature beans or mature dry beans according to harvest timing.

Recommended varieties

Soya bean ‘Elena’

Said to be the best choice for the UK climate, with a long harvest window from August to November.

Cultivar sourceAllotment Pro variety guide

Soya bean ‘Envy’

A heavy-cropping variety growing up to about 60cm tall. Its pods can be harvested green for edamame or left to mature as dry soya beans.

Cultivar sourceAllotment Pro variety guide

Soya bean ‘Black Jet’

A tough cultivar noted for cropping well even in poor summers, making it useful where summer warmth is less dependable. ## 3 - Preparing The Ground And Containers Select the warmest, sunniest and most sheltered available site. Soya beans need sustained warmth to ripen, so a south-facing plot, a position near a heat-retaining wall or a protected urban garden may give better results than an exposed allotment. Avoid shade and frost pockets. The soil should be fertile, moisture-retentive and freely drained. Before sowing or planting, incorporate at least two bucketfuls of well-rotted manure or garden compost per square metre. This supplies organic matter and helps the ground retain the regular moisture required during flowering and pod formation without becoming waterlogged. Remove perennial weeds and rake the surface to a fine, level texture for direct sowing. On heavy or cold ground, warming the soil under a cloche before sowing can improve establishment. A raised bed warms quickly and drains freely, while a large container can be positioned in a sheltered sun trap. Containers must have good drainage and enough volume to prevent rapid drying. ## 4 - Sowing And Planting Indoor sowing gives the most dependable start, particularly outside the warmest areas. Sow in April or May, placing one seed about 5cm deep in each small pot or deep module of peat-free multipurpose compost. Keep at 18–20°C for germination and provide strong light as soon as seedlings emerge. Do not let plants become chilled, waterlogged or drawn and leggy. Grow seedlings on until outdoor conditions are reliably warm. Harden them off gradually over about two weeks, initially placing them outside during mild days and bringing them under cover at night. Plant in early summer when the soil is warm and the ambient temperature is around 15°C or above. Handle the root ball gently because legumes dislike root disturbance. Set plants 15cm apart in rows 45cm apart, at the same depth as in their pots, then firm and water thoroughly. Protect young transplants from late cold nights if necessary. Direct sowing is possible from May to June when the soil has warmed to at least 15°C. Sow seeds 5cm deep and 15cm apart in rows 45cm apart. Cold, wet soil can cause seed to rot, so wait rather than sowing merely by the calendar. Covering the row with fleece can raise temperature and protect emerging seedlings, but remove or loosen it before growth becomes cramped. ## 5 - Plant Care Keep the soil consistently moist through active growth. Water especially well when flowers open and pods start to form, because drought at these stages reduces pod set and bean size. Direct water at soil level rather than repeatedly wetting the leaves, and give a thorough soak rather than frequent shallow sprinkling. Apply a generous organic mulch after the soil has warmed and plants are established. This reduces evaporation, suppresses weeds and protects shallow roots from disturbance. Weed by hand or hoe very lightly while weeds are small. Avoid deep cultivation near the plants. Most varieties form compact, self-supporting bushes and need no framework. In windy sites, or if a cultivar grows taller than expected, insert short canes and run string around the row before plants lean over. Avoid tying individual brittle stems tightly. The organic matter incorporated before planting should sustain crops in open ground. Container plants exhaust nutrients more quickly and may benefit from a balanced liquid feed once growth is vigorous, followed by a potassium-rich feed as flowering and pod formation begin. Never compensate for cool weather with excessive nitrogen, which encourages leaves rather than ripe beans. ## 6 - Harvesting For edamame, start checking pods in late summer. Pick when the pods are bright green and well filled, with the beans inside about the size of garden peas, but before pods yellow and dry. Harvest regularly as clusters reach the right stage. Cook the whole pods in boiling water for at least ten minutes, then squeeze out the beans; the tough hairy pods are not normally eaten. For mature beans, leave healthy pods on the plants until they turn dry and papery. Ripening generally begins from late September and continues into autumn. Mature pods are relatively weatherproof, so they can remain outside while drying, but collect them before prolonged wet conditions cause mould or before pods split and shed seed. Shell fully dry pods and spread the beans in a single layer in a warm, airy place until no residual moisture remains. Discard damaged, mouldy or discoloured beans. As with green beans, mature soya beans require proper cooking before consumption. ## 7 - Storing And Clearing The Crop Fresh green edamame beans are best cooked soon after picking. Short-term refrigeration is possible, and blanched beans may be frozen for later use. Do not store damp pods in a sealed warm container, as they deteriorate quickly. Store thoroughly dried mature beans in labelled airtight containers in a cool, dry and dark cupboard. Check them after storage begins for condensation or mould; if beans were not completely dry, remove them and dry further before resealing. Retain only healthy, fully mature seed if saving it for sowing, and keep each variety separately labelled. After the final harvest, cut stems at ground level rather than pulling whole plants out. Soya beans are legumes, and leaving their root systems to decompose returns organic matter and some fixed nitrogen to the soil. Compost healthy tops. Remove diseased material rather than allowing infection to persist in the bed. ## 8 - Problem Solving Poor crops most often result from insufficient warmth. Use UK-suited varieties, start plants indoors, choose a sheltered sun trap and wait for warm soil before direct sowing. Cold wet compost or soil can rot seed, while drought during flowering and pod swelling produces empty or undersized pods. Downy mildew causes pale or discoloured patches with greyish growth in humid conditions. Powdery mildew produces a dusty white coating, often when roots are dry but air is humid. Give plants good spacing and airflow, water the soil rather than foliage and remove badly affected material. Plant viruses can cause mottling, distortion and stunting; remove suspect plants and control sap-feeding pests rather than composting infected growth. Slugs and snails are most damaging to seedlings and newly planted crops. Check around shelters and containers, encourage natural predators and use barriers or other wildlife-conscious controls where necessary. Protect direct-sown rows and young plants until vigorous growth is established. - [Downy mildews](https://www.rhs.org.uk/disease/downy-mildews) - [Plant viruses](https://www.rhs.org.uk/disease/plant-viruses) - [Powdery mildews](https://www.rhs.org.uk/disease/powdery-mildews) - [Slugs and snails](https://www.rhs.org.uk/biodiversity/slugs-and-snails) --- Source: [Royal Horticultural Society](https://www.rhs.org.uk/vegetables/soya-beans/grow-your-own). Reviewed against the live RHS soya bean guide for its 20–30°C preferred temperature, 18–20°C germination, 15°C outdoor threshold, April-to-June sowing, 5cm depth, 15cm plant and 45cm row spacing, soil preparation, watering, support, two harvest stages, minimum ten-minute edamame cooking, dry-bean storage, three exact recommended profiles and four linked common problems.

Cultivar sourceAllotment Pro variety guide

Select the warmest, sunniest and most sheltered available site. Soya beans need sustained warmth to ripen, so a south-facing plot, a position near a heat-retaining wall or a protected urban garden may give better results than an exposed allotment. Avoid shade and frost pockets.

The soil should be fertile, moisture-retentive and freely drained. Before sowing or planting, incorporate at least two bucketfuls of well-rotted manure or garden compost per square metre. This supplies organic matter and helps the ground retain the regular moisture required during flowering and pod formation without becoming waterlogged.

Remove perennial weeds and rake the surface to a fine, level texture for direct sowing. On heavy or cold ground, warming the soil under a cloche before sowing can improve establishment. A raised bed warms quickly and drains freely, while a large container can be positioned in a sheltered sun trap. Containers must have good drainage and enough volume to prevent rapid drying.

Indoor sowing gives the most dependable start, particularly outside the warmest areas. Sow in April or May, placing one seed about 5cm deep in each small pot or deep module of peat-free multipurpose compost. Keep at 18–20°C for germination and provide strong light as soon as seedlings emerge. Do not let plants become chilled, waterlogged or drawn and leggy.

Grow seedlings on until outdoor conditions are reliably warm. Harden them off gradually over about two weeks, initially placing them outside during mild days and bringing them under cover at night. Plant in early summer when the soil is warm and the ambient temperature is around 15°C or above. Handle the root ball gently because legumes dislike root disturbance.

Set plants 15cm apart in rows 45cm apart, at the same depth as in their pots, then firm and water thoroughly. Protect young transplants from late cold nights if necessary.

Direct sowing is possible from May to June when the soil has warmed to at least 15°C. Sow seeds 5cm deep and 15cm apart in rows 45cm apart. Cold, wet soil can cause seed to rot, so wait rather than sowing merely by the calendar. Covering the row with fleece can raise temperature and protect emerging seedlings, but remove or loosen it before growth becomes cramped.

Keep the soil consistently moist through active growth. Water especially well when flowers open and pods start to form, because drought at these stages reduces pod set and bean size. Direct water at soil level rather than repeatedly wetting the leaves, and give a thorough soak rather than frequent shallow sprinkling.

Apply a generous organic mulch after the soil has warmed and plants are established. This reduces evaporation, suppresses weeds and protects shallow roots from disturbance. Weed by hand or hoe very lightly while weeds are small. Avoid deep cultivation near the plants.

Most varieties form compact, self-supporting bushes and need no framework. In windy sites, or if a cultivar grows taller than expected, insert short canes and run string around the row before plants lean over. Avoid tying individual brittle stems tightly.

The organic matter incorporated before planting should sustain crops in open ground. Container plants exhaust nutrients more quickly and may benefit from a balanced liquid feed once growth is vigorous, followed by a potassium-rich feed as flowering and pod formation begin. Never compensate for cool weather with excessive nitrogen, which encourages leaves rather than ripe beans.

For edamame, start checking pods in late summer. Pick when the pods are bright green and well filled, with the beans inside about the size of garden peas, but before pods yellow and dry. Harvest regularly as clusters reach the right stage. Cook the whole pods in boiling water for at least ten minutes, then squeeze out the beans; the tough hairy pods are not normally eaten.

For mature beans, leave healthy pods on the plants until they turn dry and papery. Ripening generally begins from late September and continues into autumn. Mature pods are relatively weatherproof, so they can remain outside while drying, but collect them before prolonged wet conditions cause mould or before pods split and shed seed.

Shell fully dry pods and spread the beans in a single layer in a warm, airy place until no residual moisture remains. Discard damaged, mouldy or discoloured beans. As with green beans, mature soya beans require proper cooking before consumption.

Fresh green edamame beans are best cooked soon after picking. Short-term refrigeration is possible, and blanched beans may be frozen for later use. Do not store damp pods in a sealed warm container, as they deteriorate quickly.

Store thoroughly dried mature beans in labelled airtight containers in a cool, dry and dark cupboard. Check them after storage begins for condensation or mould; if beans were not completely dry, remove them and dry further before resealing. Retain only healthy, fully mature seed if saving it for sowing, and keep each variety separately labelled.

After the final harvest, cut stems at ground level rather than pulling whole plants out. Soya beans are legumes, and leaving their root systems to decompose returns organic matter and some fixed nitrogen to the soil. Compost healthy tops. Remove diseased material rather than allowing infection to persist in the bed.

Poor crops most often result from insufficient warmth. Use UK-suited varieties, start plants indoors, choose a sheltered sun trap and wait for warm soil before direct sowing. Cold wet compost or soil can rot seed, while drought during flowering and pod swelling produces empty or undersized pods.

Downy mildew causes pale or discoloured patches with greyish growth in humid conditions. Powdery mildew produces a dusty white coating, often when roots are dry but air is humid. Give plants good spacing and airflow, water the soil rather than foliage and remove badly affected material. Plant viruses can cause mottling, distortion and stunting; remove suspect plants and control sap-feeding pests rather than composting infected growth.

Slugs and snails are most damaging to seedlings and newly planted crops. Check around shelters and containers, encourage natural predators and use barriers or other wildlife-conscious controls where necessary. Protect direct-sown rows and young plants until vigorous growth is established.

Source: Royal Horticultural Society. Reviewed against the live RHS soya bean guide for its 20–30°C preferred temperature, 18–20°C germination, 15°C outdoor threshold, April-to-June sowing, 5cm depth, 15cm plant and 45cm row spacing, soil preparation, watering, support, two harvest stages, minimum ten-minute edamame cooking, dry-bean storage, three exact recommended profiles and four linked common problems.