Soybeans (Glycine max) are a major food crop grown by farmers, but they can also be a tasty vegetable for the home garden. The pods of this warm-season annual vegetable can be harvested when plump and green and then steamed and salted for a delicious snack of edamame.
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Like most garden beans, soybeans are easy to grow in full sun and warm weather. There are many varieties of soybeans from which to choose that mature at different rates, depending on your climate's growing season.
Soybeans mature in two to three months, depending on the variety.
Soybean Life Cycle and Days to Harvest
Soybeans are planted in the spring after all danger of frost has passed, and they die back in mid to late fall. For the home garden, many growers recommend sowing in soil that is at least 60 degrees Fahrenheit. Soybean seeds germinate after two days and will emerge from the soil about a week later. Plant successive crops if you would like multiple harvests.
Choose a bush variety of soybeans when selecting seeds for the home garden. After growing 2 to 3 feet tall, the plants will bloom in the summer with small, white or pinkish-purple flowers. The flowers then develop into hairy seed pods containing two to four beans. A healthy soybean plant typically produces 50 to 100 pods, but this can vary based on the length of the growing season and growing conditions.
Depending on the variety, soybean plants mature after two to three months. However, cool conditions can slow down the development of soybeans. After reaching maturity, the plants will begin to brown and die.
Soybean Maturity Groups
Soybean development is affected by temperature and by the amount of daylight received during the growing season. Because of this, soybean varieties are categorized into maturity groups based on the length of time between planting and harvesting the bean pods. The earliest maturing soybeans are rated a 0 for northern regions, while the very latest to mature are rated a 10. Check with your local extension office to see which maturity groups grow best in your climate.
When to Harvest Soybeans and Edamame
Green soybeans harvested as a vegetable are also known as edamame. Edamame is ready to harvest when the pods are plump and bright green, usually at 2 to 3 inches long. The pods or shelled beans can be stored in the refrigerator or blanched and frozen. Besides making a tasty snack, fresh edamame can be used in rice dishes, soups, and salads.
Soybeans can also be harvested after the plants have fully matured and turned brown in the fall. Store harvested plants until they are completely dry and the seeds rattle inside the pods. Dried soybeans can be used in many recipes that incorporate dried beans as well as for tofu and soy milk.