Annual pinto beans (Phaseolus vulgaris) were first cultivated in Central and South America thousands of years ago. They can be eaten fresh when the pods are still immature, but are traditionally dried and stored for later use. Following a few basic guidelines will create the best possible conditions for growing pinto beans.
Pinto beans need warm weather to grow and can be grown in the summer in nearly all parts of the continental U.S. The only two areas where production may be difficult are the foggy coastal regions on the California coast and the cool, rainy areas of the Pacific Northwest. Wait to plant pintos until after all danger of frost has passed in spring and the ground has warmed to at least 70 degrees Fahrenheit -- otherwise the seeds may rot before they germinate.
Pintos grow best in a light, sandy loam, but can adapt to most soil types, as long as drainage is good. For best production, soil pH needs to be between 6.5 and 7. Pinto beans are a light feeding crop and will grow in soils of low fertility, but you'll get the best yields and pest resistance in fertile soil that is rich in organic matter. Like most legumes, pintos produce their own nitrogen with bacteria that live on their roots. For this reason, nitrogen fertilizer is rarely needed or beneficial for growing pinto beans.
Care and Management
Pintos need regular water throughout the growing season, but are prone to fungal diseases in excessively wet conditions. It is best to let the soil dry slightly between waterings. Regular cultivation to prevent weeds is one of the most important practices for growing pinto beans. To avoid the buildup of pests and pathogens, it is better to rotate pinto beans with other non-legume crops, than to grow them year after year in the same plot.
For best growth, pinto bean seed can be inoculated with the bacteria (Rhizobium phaeoli) that is responsible making nitrogen for leguminous plants. The bacteria occurs naturally in most soils, but more nitrogen will be produced if the seeds are coated with the bacterial inoculant just before planting. If there is cool, rainy weather when the seeds are ripening, cut the plants to the ground and hang them upside down in a warm, dry room until the seeds have dried completely. This prevents mildew from forming on the seeds and ruining the crop.