As neighbors go, pole beans make great additions to the garden community. They add nitrogen to the soil, don't take up much room, attract bees and butterflies with their ornamental flowers, and even provide support to the wobbly plants they grow upon. The trick, of course, is choosing companion plants which help the pole beans--green, wax, kidney and dozens of other varieties--as much as they aid their fellow plants.
Beans as Good Neighbors
In the Native American tradition, pole beans, corn and winter squash form the "three sisters" companion planting method. While each plant plays a part in this plant guild, beans, like all legumes, add nitrogen to the soil, helping the corn and squash yield healthier plants and bigger harvests. In addition, the beans, when planted in a circle around an ear of corn, help anchor the corn plants during stormy weather.
Extending the Benefit
Beans and other legumes provide their nitrogen-building service everywhere they are planted. "Gaia's Garden" author Toby Hemenway suggests that gardeners, rather than pulling up the entire pole bean plant at the end of the season, remove only the above-ground portion. This practice allows the root systems to slowly release more nitrogen as they decompose, making the beans just as valuable for the following year's crops.
The Other Two Sisters
Not all ideal companion planting methods provide mutual benefits, but corn and squash help pole beans as much as they benefit from them. The corn, of course, provides a trellis for the vines to climb, preventing the beans from spoiling through ground contact.
Vining squash, especially winter and pumpkin varieties, benefits pole beans by providing a prickly field over which raccoons and other pests hesitate to cross. In addition, the broad leaves of squash plants act as living mulch, preventing weeds and conserving moisture as they sprawl around the pole beans.
An Ancient Bean Pollinator
In some cultures, a fourth sibling often accompanied the "three sisters" method, according to Hemenway. The tall flowering plant known as Rocky Mountain bee plant, Cleome serrulata, appears in the folk songs and garden traditions of the Tewa tribe of New Mexico.
The cleome, which contains edible seedpods, flowers and leaves, attracts pollinating insects to pole beans. It also mines iron from deep in the soil, making the soil around the beans richer even as the beans, in return, provide nitrogen.
Cleomes aren't sturdy enough to actually hold up bean plants; use another plant or a man-made trellis for that purpose. Instead, plant cleomes alongside bean plants to help attract the pollinating insects and mineral-rich soil, which may aid in healthier and more plentiful bean production.
Organic gardeners prize summer savory--"the bean herb"--because of its beetle-deterring properties. Perhaps the greatest threat to pole beans, the larvae of the Mexican bean beetle attack bean seedlings before the vines reach their otherwise hardy stage of growth.
Plant summer savory at the base of the bean plants, where they won't be shaded by the bean trellis but will be close enough to provide protection. The North Dakota system of extension services reports that the annual herb not only deters bean beetles, but may increase bean yield and flavor. As a bonus, summer savory pairs well with green beans in cooked dishes, making the two plants' growing proximity an added blessing when harvesting them for recipes.
Additional Plants to Consider
The annual flowers marigold and nasturtiums also deter the Mexican bean beetle, as will the perennial herb rosemary. Radishes often make good all-purpose insectaries, and their early growth habit is well timed for protecting vulnerable bean seedlings. Vegetables and fruits that seem to be mutually helpful to pole beans include potatoes, carrots, celery, strawberries, eggplants and radishes.