Companion planting involves growing specific plant varieties close to one another to create a mutually beneficial environment, leading to improved growth or yield. Corn is an ideal candidate for this technique because its tall, sturdy structure and heavy nutrient requirements create unique opportunities for synergistic pairings. The practice leverages natural plant interactions, addressing needs like physical support, nutrient availability, and pest defense. By strategically selecting garden neighbors, growers can maximize the productivity of their corn patch, which needs a consistent supply of resources to thrive. This approach allows the corn to focus its energy on producing large, healthy ears.
The Three Sisters: Corn’s Classic Partners
The most historically significant companion planting system for corn is the “Three Sisters,” a traditional polyculture. This trio consists of corn, pole beans, and squash, creating a small, self-sustaining ecosystem. The corn stalks serve as the physical foundation, acting as a natural trellis that provides vertical support for the vining beans to climb toward sunlight.
The pole beans address the heavy nutritional demands of the corn. They are legumes, and their roots host specialized bacteria that convert atmospheric nitrogen into a usable form, a process called nitrogen fixation. This fixed nitrogen is released into the soil, enriching it for the nitrogen-hungry corn.
The squash component provides ground cover. The large leaves shade the ground, suppressing weed growth and reducing water evaporation, conserving moisture for all three plants. The prickly hairs often found on squash vines can also deter larger browsing animals, like raccoons or deer, from disturbing the corn.
Companions for Pest and Disease Control
Many companion plants protect corn from common pests by repelling insects or attracting beneficial predators. Aromatic herbs and flowers often contain volatile compounds that mask the scent of the corn, making it harder for pests to locate their target. Marigolds are frequently planted near corn because they release chemicals that deter a wide range of pests, including aphids and nematodes that can damage corn roots.
Herbs like basil and mint emit strong fragrances that repel certain corn pests and help deter grazing animals like deer. Mint is best grown in a container to prevent its aggressive spreading root system from competing with the corn. Other plants function by attracting beneficial insects that prey on corn pests, such as dill, which attracts ladybugs and parasitic wasps that feed on aphids and corn earworms.
Nasturtiums offer a unique strategy by acting as a trap crop, meaning they are more attractive to pests like aphids than the corn itself. By planting nasturtiums a short distance away, gardeners can draw the pests away from the main corn crop. Borage is another flower that both attracts pollinators and helps to deter destructive worms that attack corn plants.
Enhancing Soil Health and Water Retention
Beyond the nitrogen-fixing role of beans, other companions can improve the physical structure of the soil and manage moisture levels. Plants that produce extensive root systems help to break up compacted soil, improving aeration and drainage, which benefits the corn’s shallower roots. Certain cover crops, such as buckwheat, are known as soil conditioners that improve the soil’s structure and enhance the availability of phosphorus.
Other plants are used primarily as a living mulch to manage the soil surface. Low-growing vining plants like cucumbers or melons can be used to provide ground cover, cooling the soil and conserving moisture. This moisture retention is particularly helpful for corn, which is a heavy water consumer during its peak growth period.
Attracting pollinating insects, such as bees, is another indirect way companions enhance corn yield, even though corn is primarily wind-pollinated. Flowers like sunflowers can act as a windbreak for young corn and are highly effective at attracting general pollinators. Certain clovers, when used as a ground cover, can improve soil fertility and structure.
Plants That Compete: What Not to Plant Near Corn
Corn is a heavy feeder, requiring large quantities of nutrients, particularly nitrogen, to support its rapid, tall growth. Plants that also demand high levels of the same resources should be avoided, as they will directly compete with the corn, leading to stunted growth for both. Tomatoes are a poor companion because they are also heavy feeders with extensive root systems, creating intense competition for water and nutrients.
Planting tomatoes and corn together also increases the risk of shared pest infestations, as both are susceptible to the corn earworm. Similarly, brassicas like cabbage, broccoli, and cauliflower are heavy nitrogen consumers and will compete directly with the corn for this limited resource. Furthermore, the height of corn can easily shade out sun-loving, shorter crops like broccoli, which need full sun to develop properly.
Certain plants exhibit allelopathy, a phenomenon where they release chemicals that actively inhibit the growth of nearby plants. Fennel is a well-known allelopathic plant and should be kept entirely separate from corn and most other vegetables. The presence of these competing or allelopathic plants can severely reduce the overall health and yield of the corn crop.