Bush beans are a popular and efficient garden crop, characterized by a compact, non-vining growth habit that reaches about two feet in height. Unlike pole beans, these quick-growing plants are self-supporting and typically produce their harvest within a short, concentrated window, often 50 to 60 days after planting. Companion planting involves placing different plant species near each other to create a mutually beneficial environment. This strategy helps foster a balanced garden ecosystem where certain plants offer protection, enrich the soil, or improve the health of neighboring bush bean plants.
Companions for Pest Deterrence
Protecting bush beans from pests is a primary goal of companion planting, and several herbs and flowers can serve this purpose. Aromatic herbs like rosemary and summer savory are effective companions against the Mexican bean beetle. Their strong scents mask the chemical signals beetles use to locate the plants, deterring them from laying eggs.
Flowers like French or African marigolds offer protection both above and below the soil line. They release thiophene compounds from their roots, which helps to suppress or repel root-knot nematodes that damage bean roots. Nasturtiums function as a classic trap crop, acting as a decoy for pests like aphids and Mexican bean beetles, which prefer the nasturtium leaves.
Planting nasturtiums a short distance away can lure aphids away, attracting beneficial insects like lacewings and ladybugs. Dill and oregano also contribute to pest control by attracting hoverflies and predatory wasps, which feed on common bean pests such as aphids and spider mites.
Companions for Soil Enrichment and Growth
Beyond pest control, other plants offer physical and chemical benefits that create an optimal growing environment for bush beans. Beans, as legumes, form a symbiotic relationship with Rhizobium bacteria in nodules on their roots, a process called biological nitrogen fixation. This process converts unusable atmospheric nitrogen gas into ammonia, which the bean plant uses, and which also enriches the surrounding soil.
While the bean plant uses most of the fixed nitrogen during its growing season, the remaining nitrogen becomes available to neighboring plants after the bean plant dies or is harvested. This makes the bean plant an excellent partner for heavy feeders like corn. Corn can be planted with bush beans to provide light, filtered shade during the hottest parts of the day, reducing heat stress.
Root crops like radishes and carrots are beneficial because their root structures occupy different soil depths than the shallow roots of bush beans, minimizing competition for nutrients and water. Radishes germinate quickly and loosen compacted topsoil as they grow. This natural soil-breaking action improves aeration and allows water to penetrate the surface more easily.
Plants That Inhibit Bush Bean Growth
Not all plants are beneficial neighbors, and certain species should be avoided as they inhibit the growth or health of bush beans. The most well-known antagonists are members of the Allium family, including onions, garlic, chives, and leeks. These plants are thought to exude compounds that negatively affect the Rhizobium bacteria necessary for nitrogen fixation.
Interfering with this beneficial bacteria stunts the bean plant’s growth by preventing it from accessing necessary nitrogen. Members of the Brassica family, such as cabbage, broccoli, and kale, are also problematic. These heavy feeders require large amounts of nutrients, leading to intense competition that depletes resources the beans need for a full harvest.
Another plant to be mindful of is the sunflower, which exhibits allelopathy. This is a process where a plant releases biochemicals that inhibit the growth of nearby plants. The chemicals released by sunflowers can suppress the bean plant’s development, reducing the overall productivity of the bean crop.
Arranging Your Companion Garden
Successfully integrating companion plants requires a thoughtful approach to layout and timing. Bush beans are typically planted in rows spaced 18 to 24 inches apart, with seeds placed every three to six inches within the row. This dense planting is possible because the compact plants do not require vertical supports.
To interplant, fast-growing root vegetables like radishes should be sown directly in the bean row or in a dedicated row between the bush bean rows. Radishes are harvested quickly, often within three to four weeks, before the beans mature. This creates space and loosens the soil for the developing bean roots.
Herbs and flowers intended for pest deterrence, such as marigolds, rosemary, or summer savory, should be scattered throughout the bean patch. Interspersing these aromatic companions helps to confuse and repel pests across the entire area. This creates a protective barrier for the bean plants.