How to Grow Soybeans

Soybeans are bushy, free-branching, warm-weather annuals. There are more than 10,000 soybean cultivars. Seeds can be smaller than a pea or as large as a kidney bean.

Soybeans grow 12 to 36 inches (30-91cm) tall. Stems and leaves are hairy. The 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. Seeds range from black to gray, brown, green, yellow, white, and striped.

Soybean Quick Growing Tips

• 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).
• Soybean yield: grow 4 to 8 soybean plants per household member.

Where to Plant Soybeans

• 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.

Soybean 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 Soybeans

• 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.

Soybean Companion Plants

• Grow soybeans with potatoes, cucumbers, corn, strawberries, celery, summer savory.
• Do not plant soybeans with onion or garlic.

Watering and Feeding Soybeans

• 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.

Soybean 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

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

Soybean 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.

Soybean 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 Soybeans

• 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 Soybeans

• Green shelled or unshelled soybeans will keep in the refrigerator for up to 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.

Soybean 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.

About Soybeans

• Common name. Soybean
• Botanical name. Glycine max
• Origin. East Asia