Companion planting involves strategically placing different plant species near one another to create a mutually beneficial environment. For potato cultivation, this technique enhances crop health and productivity by leveraging a plant’s ability to repel pests, attract helpful insects, or improve soil conditions. The goal is to maximize the harvest by protecting developing tubers from common threats. Understanding which plants support potato growth and which ones hinder it is key to a successful and abundant yield.
Beneficial Companions for Pest Control and Growth
Plants that offer a positive benefit to the potato crop operate through three primary mechanisms: pest deterrence, nutrient cycling, and creating ground cover. Aromatic herbs and flowers are effective at pest control because they emit volatile organic compounds that confuse or repel harmful insects. Marigolds, for example, suppress soil-borne nematodes through the chemical release of alpha-terthienyl from their roots, protecting the underground tubers from damage.
Catnip and cilantro provide protection against the Colorado potato beetle, a major threat to potato foliage, as their scents act as natural insect repellents. Cilantro, when allowed to flower, attracts beneficial predatory insects like ladybugs and hoverflies, which prey on soft-bodied pests such as aphids. Alliums like chives and onions emit pungent sulfur compounds that deter common garden pests, including beetles and aphids. Chive flowers also attract hoverflies, whose larvae consume aphids.
Legumes, such as bush beans and peas, enhance soil fertility through a symbiotic relationship with Rhizobium bacteria, which perform nitrogen fixation. This process converts atmospheric nitrogen into a usable form, providing nutrients to the heavy-feeding potato plants. Horseradish, a root crop, is often planted at the end of potato rows because its aroma is thought to repel the Colorado potato beetle and may improve the potato plant’s disease resistance.
Nasturtiums function as a trap crop, luring pests like aphids and beetles away from the main potato crop. They draw pests to their foliage, allowing for easy removal or containment of the infestation. Low-growing leafy greens, such as spinach and lettuce, can be interplanted between potato rows to maximize space and provide ground cover. These shallow-rooted plants do not compete with potatoes for nutrients and help keep the soil cool and moist, benefiting tuber development.
Plants to Avoid: The Worst Neighbors for Potatoes
Avoiding certain plants is as important as choosing beneficial companions, because some species compete heavily for resources or act as disease reservoirs. This involves members of the nightshade family (Solanaceae), including tomatoes, peppers, and eggplants. These plants share a genetic susceptibility to the same diseases and pests as potatoes, creating a high-risk environment.
Planting these relatives together creates a “blight hotspot,” making the entire crop vulnerable to fungal diseases like Late Blight (Phytophthora infestans). They also attract the same insects, such as the Colorado potato beetle, allowing the pest population to build up and move easily between crops. Other root vegetables, including carrots, turnips, and parsnips, should be avoided because they compete directly with the developing potato tubers, resulting in smaller harvests for both crops.
Fennel and sunflowers actively inhibit potato growth through allelopathy. Fennel releases chemical compounds that can stunt the growth of nearby plants, making it a poor neighbor for almost any vegetable. Sunflowers are heavy nutrient feeders and cast significant shade as they mature, which interferes with the sunlight required for the potato plant’s foliage to produce energy. Raspberries are also detrimental, as they are prone to fungal diseases that can easily spread to potato plants.
Maximizing Companion Planting Success (Placement and Timing)
Successful companion planting requires considering both placement and timing to avoid disrupting the growth cycle of the underground tubers. The potato plant requires “hilling,” where soil is mounded around the stems as they grow. This protects developing tubers from sunlight, preventing them from turning green and toxic. Companions must be positioned so they do not interfere with this process.
Fast-growing, shallow-rooted companions like lettuce or basil are suited for intercropping, planted close to the potato seed pieces. They will be harvested before the potato plant reaches its full size and heavy hilling begins. Taller deterrent plants, such as horseradish or large clusters of marigolds, are utilized as border planting at the ends of rows to create a protective barrier. For nitrogen-fixing legumes, planting them simultaneously with the potatoes ensures nitrogen is cycled into the soil during the potato’s early, nutrient-hungry growth phase.
Spacing between plants is important to prevent competition for water and nutrients, even with non-competing species. Maintain the standard 12 to 15-inch spacing between potato plants while placing beneficial companions in the row or on the border, about 6 to 12 inches away. Utilizing bush varieties of beans and avoiding vining types is also important, as vining plants can sprawl over the potato foliage, blocking sunlight and making the hilling process difficult.