Wait for warm soil to plant beans

Last Updated: 
May 7, 2010

CORVALLIS, Ore. – Want to know the key to success in starting bean plants? "Use a thermometer," said bean expert Jim Myers.

Most beans will germinate at about 50 degrees, but at temperatures that cool, bean seeds tend to crack, allowing access to microbes, explained Myers, an Oregon State University vegetable breeder.

Beans grown at home are fresh and flavorful, but don't be in a hurry to plant. The soil needs to be at least 60 degrees for beans to produce a healthy and vigorous seedling. The best way to make sure the soil has warmed enough – usually from late April into July – is to insert a thermometer into the soil.

White-colored bean seeds are particularly sensitive to cracking, and he recommends planting darker-colored bean seeds if you plant them before the soil warms to 60 degrees.

"It is better to plant on the late side of May, rather than risk cold snaps, and you can plant through June," Myers said. "Plant another batch in July and you may get a fall crop, depending on how soon frost arrives in your area.

"It also is better to plant into a moist seed bed rather than planting dry and watering up," Myers added. "The combination of cold and wet soil is particularly deadly to white-seeded beans."

Home gardeners can grow several types: bush beans, pole beans, runner beans, dry beans, lima beans, wax beans, snap beans, French filet, Haricot vert and edamame. Many of the varieties grown commercially in the Pacific Northwest and by home gardeners today were developed at OSU. Recommended vegetable varieties for 2010 can be found online.

"Runner and lima beans are a different species than the common bean," Myers said. “Scarlet runner beans often are used as an ornamental although they can be eaten. Lima beans are usually shelled. The large-seeded 'Fordhook' limas require a long season, and growers in our region do better with the small-seeded baby limas."

Bush beans were bred to save the cost of trellises needed for pole beans and to allow mechanical harvest. They include French filet beans, coveted by gourmets for their texture and flavor and harvested at a young age, when the pods are no more than a quarter inch in diameter.

Plant bush bean seeds two to three inches apart and one inch deep in rows 18 to 36 inches apart in a sunny, well-drained area. They are ready to harvest about three weeks after flowering. Keep plants picked for more production.

Pole beans should be planted like bush beans, except they have to be trellised or grown up a pole. If planting at the bottom of poles, plant about six seeds at the base of each.

Edamame are a specialty soybean. Pods are picked when green and boiled in salted water with the beans inside for a healthy snack. Grow them like bush beans.

Beans are subject to several viruses, root disorders and white and gray mold, Myers said. Avoid watering the foliage, remove dead plants at the end of the season and rotate crops from year to year.

Author: Judy Scott
Source: Jim Myers