RHS Growing Guides
How to grow soya beans
Our detailed growing guide will help you with each step in successfully growing Soya beans.
Getting Started
Soya beans grow best in warmer parts of the UK, as they need a long hot summer to crop well. The short pods of small round beans can be harvested when still green and immature, as edamame beans, or allowed to mature for drying and using over winter.
Given lots of sun, warmth and water, soya plants will produce clusters of furry pods by late summer
Soya plants produce short hairy pods containing two or three small rounded beans. These can be harvested at two different stages, from late summer into autumn:
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when the beans are the size of garden peas, still green and immature, for cooking and adding to salads, stir-fries and many other dishes. These are usually known as edamame beans
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when the pods are fully ripe and dry – the mature soya beans inside can be stored for use in stews and other hearty winter dishes
Soya beans can be grown from seed sown indoors or outside. They form bushy plants about 60cm (2ft) tall, depending on the variety, and don’t usually need supports. The beans are a good source of protein and fibre, but they must always be cooked before eating, to get rid of any natural toxins.
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Choosing
You can pick young, plump, green pods for edamame beans, or leave them to mature into soya beans
What and where to buy
Soya and edamame bean seeds are available in some larger garden centres and from several online seed suppliers, but the choice of varieties is currently quite limited. Young plug plants may also be available in late spring and early summer, from similar sources.
Recommended Varieties
Said to be the best variety for the UK climate. Harvest from August to November.
Heavy-cropping plants up to 60cm (24in) tall. Harvest as green edamame beans or as mature soya beans.
Preparing the Ground
Choose a warm, open, sunny growing site, ideally with light, free-draining soil. Weed thoroughly, then fork in lots of home-made garden compost or well-rotted manure – at least two bucketfuls per square metre/yard. Ideally do this a few weeks before sowing or planting out, to allow the ground to settle. Alternatively, if you're practising no-dig, mulch the soil ahead of sowing or planting directly into the mulch.
Sowing
Soya beans can be sown indoors in April and May, or outdoors in May and June. Sowing indoors is generally a more reliable option – the warmth ensures good germination rates and you can sow earlier, to give a longer growing season. It also ensures mice don’t eat the seeds, and keeps the seedlings out of reach of slugs and snails until larger and more robust.
Sowing indoors
In mid- to late spring, sow soya beans in small pots or modular trays filled with moist peat-free seed compost, inserting them 5cm (2in) deep. Place in a propagator, or cover with a clear polythene bag, and keep at 18–20°C (64–68°F). For more sowing tips, see our guides below.
Once seedlings appear, remove from the propagator or uncover, then keep in a warm, bright location, watering regularly. Move the seedlings into larger pots when roots appear through the drainage holes. They should be ready to plant out in late May or early June – see Planting, below.
Sowing outdoors
You can sow soya beans outdoors once the soil has warmed to at least 15°C (60°F) in late spring or early summer. Sow seeds 5cm (2in) deep, 15cm (6in) apart, in rows 45cm (18in) apart, then cover with cloches or plastic-free fleece. Protect the seedlings from slugs and snails, especially in damp weather.
Planting
Wait until early summer, when temperatures are around 15°C (60°F), before planting indoor-raised soya plants or young bought plants outside. Harden them off, to avoid a check in growth, and make sure your planting site is prepared in advance (See Preparing the ground above).
Water the young soya plants well, both before and after planting, and space them 15cm (6in) apart, with 45cm (18in) between rows. After watering in, cover the plants with cloches or plastic-free fleece to keep them warm while they get established.
Plant Care
Keep soya plants well watered in dry spells while the pods are forming
Mulching
Spread a deep mulch of garden compost around the plants after planting to help hold moisture in the soil and deter weeds.
Supporting plants
Most soya bean varieties sold in the UK grow to about 60cm (2ft) tall and are self-supporting. But in a windy site, or if you choose a taller variety, insert sturdy bamboo canes at the ends of the rows and loop string around them to hold the plants upright.
Harvesting
Harvest the dried pods through autumn, for cooking straight away or for storing to use later
Edamame beans are immature soya beans, harvested in summer when the pods are still green, with plump green beans inside. They can either be shelled or cooked in the pods (then shelled), and must be boiled for at least ten minutes to destroy their natural toxins.
Mature soya beans are ready for harvesting from late September, when the leaves start to fall from the plants, often leaving just brown stems with lots of hanging pods. The pods remain weatherproof during autumn, so you can pick as needed. After harvesting, remove the beans from their dry pods, then either cook straight away or spread them out on a tray indoors to dry fully. Store the dry beans in an airtight container for use over winter. As with the immature beans, cook mature soya beans thoroughly to remove any natural toxins.
Once harvesting has finished, cut plants down to the base and compost them. However, as legumes (peas, beans and related plants) fix nitrogen from the air at their roots, leave these in the ground to boost soil nitrogen levels.
Problems
Soya beans are easy to grow and generally trouble-free, as long as they’re kept warm and well watered throughout the growing season. In cool summers or colder regions, cropping may be reduced. Take care not to plant them out too early, and protect them with cloches or plastic-free fleece to keep them warm while they get established. Seedlings and young plants are vulnerable to slugs and snails – see Common problems, below.
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