Soybeans

People started growing and eating soybeans three thousand years before the invention of written language. Originally from East Asia, this high protein legume is now found practically everywhere. Soy milk, tofu, and soy sauce are just a few products made from soybeans, but what about the plants themselves? Is there a place for soybeans in your summer garden?

Soybean fruit (H. Zell) CC BY-SA 3.0

The soybean plant

Mature soybean plants can reach 2 to 4 feet tall, and they have trifoliate leaves. This means that each leaf is made up of three leaflets. Like other legumes, soybean roots have a symbiotic relationship with certain soil bacteria (Rhizobium) that help them use atmospheric nitrogen. They are deep rooted plants, going down 3 to 5 feet. Soybeans are photoperiodic plants. This means shortening days is what triggers them to start producing flowers. Soybean plants have small, self-fertile flowers that can be purple, pink, or white. Once flower production begins, many soybean plants drop their leaves.

Small, purple soybean flowers (Huwmanbeing) Public Domain

Soybean fruits are 3 inch long, hairy pods that contain 2-4 seeds, called pulses. Soybean pulses can be brown, black, green, yellow, or multicolored. By 2010, 93% of soybeans grown commercially in the U.S. were genetically modified. In that same year, scientists mapped the soybean genome, the first bean to be sequenced.

Types of soybeans

There are two basic categories of soybeans: vegetable and field. Field soybeans are grown for oil production. Vegetable varieties are higher in protein, easier to cook, and taste better than field soybeans. Soybeans contain 38-45% protein and up to 19% oil.

How to grow soybeans

Soybeans (Glycine max) are an annual bean plant that loves hot, summer weather. Pulses should be planted 1 inch deep and spaced with mature sizes in mind. To provide an ongoing harvest, you may want to use succession planting, adding new plants every week or two during the growing season. Soybeans are ready to harvest within 80-120 days after planting. Pick pods while they are still green. Once they brown, the pulses lose flavor. Of course, you can always use mature pulses to plant the next season's crop! Because of their nitrogen-fixing ability, soybeans make an excellent player in crop rotation plans.

Mature soybeans (USDA) Public Domain

Soybean pests and diseases

Spider mites are the most destructive pest of soybeans, followed by corn earworm moths, Mexican bean beetles, bean leaf beetles, and cyst nematodes. Fungal diseases, such as stem blight, rust, and white mold can infect soybean plants, along with bean yellow mosaic and other viral diseases. But don't let that stop you!

If you have the space, give soybeans a try in your yard!