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How to grow soybeans

Find out how to grow soybeans or edamame, in our Grow Guide.

Published: Wednesday, 2 June, 2021 at 11:52 am

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Plant size

Spacing

45cm between rows

Edamame or soybean is a versatile cropping plant, producing pods that can be steamed and then shelled for the tender fresh beans, or mature beans that can be dried to store for a long period before cooking. Edamame is the name given to the young beans while soybean refers to the mature bean.

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

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.

Soybeans are tender warm-weather legumes. Sow soybeans in spring 2 to 3 weeks after the average last frost date when the soil has warmed to at least 60°F (16°C). Soybeans can be planted earlier in warm-winter regions. Soybeans grow best where the daytime temperature averages in the 70°sF (21°C).

Description. The soybean is a bushy, free-branching annual legume. It grows 12 to 36 inches (30-91cm) tall. Stems and leaves are hairy. Flowers are white with lavender shading. Pods grow 1 to 4 inches (2.5-10cm) long in clusters of three to five. Each fuzzy pod contains 2 to 4 seeds. There are more than 10,000 soybean cultivars. Colors range from black to gray, brown, green, yellow, white, and striped. Seeds can be smaller than a pea or as large as a kidney bean.

Yield. Grow 4 to 8 soybean plants per each household member.

Planting Soybeans

Site. Plant soybeans in full sun; soybeans will tolerate partial shade but the yield will be reduced. Soybeans grow best in loose, well-drained soil rich in organic matter. Soybeans prefer a soil pH of 6.0 to 6.8. Soybeans are tolerant of poor soil.

Planting time. Sow soybeans in spring 2 to 3 weeks after the average last frost date when the soil has warmed to at least 60°F (16°C). Soybeans grow best where the daytime temperature averages between 60°F and 70°F (16-21°C). Plant soybeans in late winter in warm-winter regions. Soybeans are not frost-tolerant.

Planting and spacing. Sow soybean seeds 1 to 2 inches (2.5-5cm) deep, 2 to 4 inches (5-1ocm) apart in rows 24 to 30 inches )61-76cm) apart. Thin successful seedlings from 4 to 6 inches (1015cm) apart; cutaway thinned seedlings with scissors at ground level being careful not to disturb the roots of remaining plants. Do not soak seed before planting and do not overwater immediately after planting; too moist seeds may crack and germinate poorly.

Companion plants. Potatoes, cucumbers, corn, strawberries, celery, summer savory. Do not plant soybeans with onion or garlic.

Caring for Soybeans

Water and feeding. Keep planting beds evenly moist until soybeans have pushed through the soil. Water regularly during flowering and pod formation. Avoid overhead watering which can cause flowers and pods to fall off. Mulch when the soil warms to greater than 60°F (16°C) to conserve soil moisture. Add aged compost to planting beds in advance of planting. Side dress soybeans with aged compost at midseason. Avoid adding nitrogen-rich fertilizers to planting beds. Soybeans, like other legumes, set up a mutual exchange with soil microorganisms called nitrogen-fixing bacteria to produce nitrogen compounds used by the plant.

Care. Avoid handling soybeans when they are wet or covered with heavy dew; this may spread fungus spores. Keep planting beds weed-free; cultivate around soybeans carefully so as not to disturb the plant’s shallow root system. Mulch to conserve soil moisture once the soil has warmed. Rotate soybeans and other legumes to add nitrogen to the soil.

Container growing. Soybeans can be grown in containers 8 inches deep, the space required for a useable crop makes soybeans a poor choice for container growing.

Pests. Soybeans are rarely bothered by pests. Keep the garden clean and free of debris so that pests can not harbor or over-winter in the garden.

Diseases. Soybeans are rarely attacked by a disease. Rotate beans so that they do not grow in the same location more than every three years.

Harvesting and Storing Soybeans

Harvest. For green shell beans, harvest soybeans when pods are green, full, and plump, usually 2 to 3 inches (5-7cm) long, about half mature. Soybeans for shelling and fresh use are ready for harvest 45 to 65 days after sowing. Dry soybeans require 100 or more days to reach harvest. Soybeans reach maturity at the same time; pull the whole plant and hang it upside down to dry. Shell dry beans once the pods are fully dry.

Note: Soybeans should not be eaten raw; they contain trypsin inhibitor which prevents the digestion of proteins. Blanch green soybeans in boiling water for a couple of minutes and then plunge them into an ice-water bath. Boil sprouted beans for at least 5 minutes before eating.

Storing. Green shelled or unshelled soybeans will keep in the refrigerator for up one week. Shelled soybeans can be frozen, canned or dried. To make shelling easier, drop pods into boiling water for a minute. Dried, shelled soybeans can be stored in a cool, dry place for 10 to 12 months.

Varieties. There are more than 10,000 soybean cultivars. Green-seed cultivars are considered the most tender and best flavored. Black-seeded beans are used for drying. Yellow-seed beans are used to make soy milk and flour. Select a cultivar suited to your growing region; check with the nearby agricultural extension for recommendations.

An ancient crop of the Orient, soybeans (Glycine max ‘Edamame’) are just beginning to become an established staple of the Western world. While it’s not the most commonly planted crop in home gardens, many people are taking to growing soybeans in fields and reaping in the health benefits these crops provide.

Information on Soybeans

Soybean plants have been harvested for more than 5,000 years, but only in the last 250 years or so have Westerners become aware of their enormous nutritional benefits. Wild soybean plants can still be found in China and are beginning to find a place in gardens throughout Asia, Europe, and the Americas.

Soja max, the Latin nomenclature comes from the Chinese word ‘sou,’ which is derived from the word ‘soi‘ or soy. However, soybean plants are so revered in the Orient that there are over 50 names for this extremely important crop!

Soy bean plants have been written about as early as the old Chinese ‘Materia Medica’ circa 2900-2800 B.C. However, it doesn’t appear in any European records until A.D. 1712, after its discovery by a German explorer in Japan during the years 1691 and 1692. Soybean plant history in the United States is disputable, but certainly by 1804 the plant had been introduced in eastern areas of the U.S. and more fully after an 1854 Japanese expedition by a Commodore Perry. Still, the popularity of soybeans in the Americas was limited to its use as a field crop even as recently as the 1900’s.

How to Grow Soybeans

Soybean plants are fairly easy to grow– about as easy as bush beans and planted much the same way. Growing soybeans can occur when soil temperatures are 50 degrees F. (10 C.) or so, but more ideally at 77 degrees F. (25 C.). When growing soybeans, don’t rush planting as cold soil temperatures will keep the seed from germinating and stagger planting times for a continuous harvest.

Soybean plants at maturation are quite large, 2 feet (61 cm.) tall, so when planting soybeans, be aware that they are not a crop to attempt in a small garden space.

Make rows 2 to 2 ½ feet (61-76 cm.) apart in the garden with 2 to 3 inches (5-8 cm.) between plants when planting soybeans. Sow seeds 1 inch (2.5 cm.) deep and 2 inches (5 cm.) apart. Be patient; germination and maturation periods for soybeans are longer than most other crops.

Growing Soybean Problems

  • Don’t sow soybean seeds when the field or garden is overly wet, as cyst nematode and sudden death syndrome may affect the growth potential.
  • Low soil temperatures will prevent germination of the soybean plant or cause root rotting pathogens to flourish.
  • In addition, planting soybeans too early may also contribute to high populations of bean leaf beetle infestations.

Harvesting Soybeans

Soybean plants are harvested when the pods (edamame) are still an immature green, prior to any yellowing of the pod. Once the pod turns yellow, the quality and flavor of the soybean is compromised.

Pick by hand from the soybean plant, or pull the entire plant from the soil and then remove pods.

All plants require certain nutrients to grow. While most plants attain their nutrients from the soil, soybeans are a unique type of plant called a legume that are able to obtain nitrogen from the atmosphere. Soybeans do this by forming a mutually beneficial relationship with a certain bacterium in their root nodules. The bacterium convert the nitrogen to a plant-soluble form and in return are supplied with carbohydrates. Many farmers choose to plant soybeans because soybeans require less nitrogen fertilizer and help restore the important nutrient to the field. After harvest, farmers may choose to plant a crop like winter wheat, which requires high quantities of nitrogen.

Selecting Seed

Like many field crops, soybeans are grown from seed in the field from a previous harvest. The soybean seeds are mature soybeans that are cleaned and bagged specifically for use as seed. Farmers select seed based on desirable plant characteristics, like high yield, ability to withstand drought, color, or ability to withstand wind and weather.

Planting

In North Carolina, farmers plant soybeans beginning in May and as late as July. Seed may be planted in cultivated or tilled land by a tractor and a planter which deposits the soybean seed about 1 1⁄2 inches deep in rows that are up to 30 inches apart. There is no rule about how wide rows must be, but 30 inches is typical.

Alternatively, soybeans may be “drilled” into the ground in seven-inch rows by a special “no-till” planter. When a farmer uses the no-till method, the land is not cultivated and the seeds are planted directly into the stubble left over from the previous crop, such as wheat harvested in May or June. The no-till method saves time, conserves soil moisture and greatly decreases the possibility of soil erosion. No-till is highly desirable, but if farmers are dealing with fields infested by weeds or other pests, till may be necessary to eradicate the pest.

Growth

Soybeans sprout about four to seven days after planting. At his point, the farmer has already invested heavily in seed, pest controls, and operation costs, so there are many things a farmer must consider to protect his crop. Bugs and worms really like small tender plants, so when the farmer notices there is a heavy insect infestation, he or she must calculate the degree of risk to the crop. If the infestation is bad enough to harm the crop, the farmer sprays a pesticide to control the pest. If the farmer is using organic methods, there are still products that can be sprayed but the choice is much more limited, and the risk is somewhat greater.

Weed that will inhibit soybean growth

Another threat to the young crop comes from weeds that grow faster than soybean plants. They can crowd out the soybean plants and prevent necessary sunlight and nutrients from enabling the soybean plants to grow. This will reduce the soybean yield. If allowed to grow, some weeds will produce seeds that will be harvested with the soybeans and will reduce the value. The farmer will get less money when they sell the crop post-harvest.

Soybean plant flowering

In July, August and September, the plants bloom. The flowers are small and vary from a white to a beautiful violet or purple. From these blossoms, the soybean plant grows small pods that contain the young seeds. The soybean is a self-pollinating plant, which means that each flower has male and female parts. A single plant can produce seed and essentially clone itself. Soybean plants produce many more flowers than they need, so many flowers never produce pods. Soybeans are a deep green with a slightly paler shade of silver-green on the underside of the leaf.

About 75% of North Carolina soybeans are grown in the eastern part of the state, and if you are driving in this part of the state in the summer and early fall, you are sure to see some soybeans. To learn more about where and how many soybeans are produced in N.C., check the NC Department of Agriculture & Consumer Services annual Agricultural Statistics book.

Harvest

In late September, the soybeans begin to mature. As the days get shorter and the temperatures get cooler, the leaves on soybean plants begin to turn yellow. By mid-October and November, the leaves will turn brown and fall off, exposing the matured pods of soybeans. The soybeans are now ready to be harvested.

Combines are large machines for harvesting soybeans and other grains including corn and wheat. The header on the front of the combine cuts and collects the soybean plants. The combine separates the soybeans from their pods and stems and collects the soybeans into a holding tank in the back of the combine. When the tank is full, the combine operator will empty the soybeans into a grain truck or grain wagon.

Soybeans are either taken directly to a grain dealer in the grain trucks or they are taken to storage facilities and stored until the farmer decides to sell them. Ultimately the soybeans are transported to a processing plant where the soybean meal (the protein component of the bean) is separated from the soy oil components.

Originating from South-East Asia, these beans usually need a long, hot summer of 20–30°C (68–86°F), although some newer varieties can cope in cooler conditions. They are an excellent source of protein and can either be picked and cooked when still green, or left to mature, then dried and stored.

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Jump to

Soya beans can be sown indoors or outdoors, in May or June.

The easiest option is to sow outdoors once the soil has warmed up in late spring, ideally under fleece or cloches.

They like a warm, sunny, sheltered spot, and fertile, free-draining soil. Sow the seeds 5cm (2in) deep, 15cm (6in) apart, in rows 45cm (18in) apart.

You can also sow indoors, in 7.5cm (3in) pots or seedtrays filled with seed compost, setting the seeds 5cm (2in) deep. Water gently, then place the pot or tray in a propagator, or cover with a clear polythene bag, and keep at a temperature of 18–20°C (64–68°F).

Once the seedlings appear, remove from the propagator or uncover, then place in warm, bright location. Move the seedlings into larger pots when roots appear through the drainage holes.

Gradually acclimatise indoor-sown plants to outdoor conditions (harden off), before planting out after all risk of frost has passed.

Choose a warm, sunny site with well-drained but moist soil. Space the plants 15cm (6in) apart, in rows 45cm (18in) apart. Cover the surrounding soil with a thick layer of mulch, such as garden compost, to help retain moisture.

Plants can grow up to 1.2m (4ft) tall, but are usually self-supporting.

Hoe around plants regularly and keep them well watered.

Harvesting

You can harvest the beans either unripe (known as edamame beans) or fully ripe as dried soya beans.

Edamame beans are immature soya beans, harvested in summer while the pods are still green, with plump beans inside. They can either be shelled or cooked in the pods, and must be boiled for at least 10 minutes to destroy any toxins.

Ripe 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 required.

The beans are easy to store on the plants or in airtight containers.

Soya beans must not be eaten raw – boil them for at least 10 minutes to get rid of toxins.