Companion planting involves strategically placing different plant species near one another to create a mutually beneficial environment. When grown together, certain plants can enhance growth, repel pests, or improve soil health for their neighbors. Corn, a staple crop with high nutrient and structural needs, benefits tremendously from this ancient method. By selecting appropriate garden partners, growers can manage common challenges like soil depletion and pest infestations without excessive intervention.
The Foundation Understanding the Three Sisters
The most recognized example of corn companion planting is the “Three Sisters,” a traditional agricultural system developed by Indigenous peoples of North and Central America. This triad consists of corn, climbing beans, and squash, each playing a specific functional role. The combination creates a self-sustaining ecosystem that supports all three plants better than if they were grown separately.
Corn serves as the supportive sister, providing the necessary vertical structure for the climbing beans. The tall, sturdy stalks act as a natural trellis, allowing bean vines to reach sunlight and stabilizing the corn during strong winds. This minimizes the need for external staking while maximizing the use of vertical space.
Beans are the nourishing component, engaging in a symbiotic relationship with Rhizobia soil bacteria. These bacteria form nodules on the bean roots, converting atmospheric nitrogen into a usable form through nitrogen fixation. This natural fertilization replenishes the soil, directly benefiting the nitrogen-hungry corn and the sprawling squash.
The third sister, squash, provides ground cover with its broad, sprawling leaves. This dense foliage acts as a living mulch, shading the soil to retain moisture and suppress competing weeds. Furthermore, the large, sometimes prickly leaves of certain squash varieties deter larger pests like raccoons from approaching the corn ears.
Functional Companions Pest and Weed Management
Many other plants offer distinct benefits when grown near corn, primarily focusing on protection and microclimate management. These functional companions can be grouped by the specific ecological service they provide, such as pest deterrence or soil health improvement.
Pest deterrence often relies on aromatic plants that release volatile compounds to confuse or repel insects. Planting herbs like thyme near corn can help repel the corn earworm. Marigolds are popular companions because they emit a strong scent that repels various pests, including aphids, and some varieties are effective against root-knot nematodes in the soil.
Other plants improve the garden’s microclimate or soil health. Low-growing plants, such as lettuce or white clover, act as a living mulch between corn rows, shading the soil and suppressing weeds. White clover, as a legume, also contributes soil nitrogen. Flowers like dill and borage attract beneficial insects, such as parasitic wasps and ladybugs, which prey on common corn pests.
What to Avoid Plants That Compete with Corn
A successful companion planting strategy involves knowing which plants should be kept away from the corn patch to prevent resource competition and pest overlap. Corn is a heavy feeder, requiring large amounts of nitrogen throughout its growth cycle, making it susceptible to competition from other nutrient-demanding crops.
Aggressive nutrient competitors, especially for nitrogen, should be avoided, such as members of the Brassica family (broccoli, cabbage, and cauliflower). These heavy feeders compete directly with corn for finite soil resources, potentially stunting the growth of both crops. Since corn grows tall, it also casts significant shade, which can inhibit the growth of sun-loving Brassicas.
Another major concern is the sharing of common pests, which can lead to rapid infestation. Tomatoes and eggplants are poor companions because they are susceptible to the same damaging insects, like the corn earworm and the tomato hornworm. Planting these crops in close proximity increases the likelihood of pests spreading.