Companion planting involves placing different plant species near each other to create a mutually beneficial environment. This technique helps maximize garden health and yield by leveraging natural plant relationships, such as pest repulsion and nutrient sharing. Potatoes are a heavy-feeding crop that takes up significant underground space, and they benefit greatly from careful placement to ensure a strong harvest.
Plants That Enhance Potato Growth
Legumes, such as peas and bush beans, are highly beneficial because they partner with bacteria in the soil to convert atmospheric nitrogen into a form usable by plants. This process, known as nitrogen fixation, helps replenish the soil with a nutrient that the heavy-feeding potato plants rapidly deplete during their early growth stages.
Herbs and aromatic flowers are effective for pest management, using strong scents to deter harmful insects. Alliums, including garlic and chives, release volatile organic compounds that confuse and repel pests like the Colorado potato beetle. Planting herbs such as basil or cilantro nearby can also help mask the potato plants’ scent, making it harder for pests to locate them.
Certain flowers, notably French marigolds and nasturtiums, serve as a protective barrier against various insects. Marigolds are thought to emit chemicals from their roots that can deter specific nematodes, which are microscopic soil worms that can damage potato tubers. Nasturtiums serve a dual purpose by repelling beetles and aphids, and their sprawling habit acts as a natural ground cover to suppress weeds and retain soil moisture.
Shallow-rooted vegetables, like the cabbage family (brassicas) and spinach, make excellent companions because they do not compete with the deep-growing potatoes for underground space. These plants utilize the upper layers of the soil and can fill the space between potato rows. This complementary growth habit maximizes the use of garden space without creating competition for water or nutrients, allowing both crops to thrive.
Plants to Avoid
The plants to avoid are other members of the Solanaceae or nightshade family, which includes tomatoes, peppers, and eggplant. These relatives are all susceptible to the same fungal diseases, such as early and late blight, and attract the same pests, including the Colorado potato beetle. Planting them together creates a high-risk environment where pathogens and insects can quickly spread between crops.
Heavy feeders like corn, squash, and sunflowers require large amounts of water and nutrients, directly competing with potatoes for the resources they need to form tubers. When grown too closely, the competition for moisture and soil fertility can result in significantly reduced potato yields.
Certain root vegetables should also be kept separate to prevent underground competition for physical space. Carrots, parsnips, and turnips develop their edible parts in the same soil depth zone as the potato tubers. This shared territory leads to stunted growth in both crops as their underground structures physically interfere with one another. Furthermore, allelopathic plants, such as fennel, release chemicals into the soil that can inhibit the growth of nearby plants, making them detrimental companions for virtually all vegetables, including potatoes.
Strategic Planting and Spacing
Placing pest-repelling herbs and flowers, such as thyme or marigolds, along the edges or at the ends of potato rows is often more effective than interplanting them directly within the rows. This border strategy creates a fragrant perimeter that deters insects without crowding the main crop.
For space-maximizing companions, like shallow-rooted brassicas or spinach, interplanting them between the potato hills is an ideal use of the garden bed. This approach utilizes the vertical space above the tuber zone and provides a living mulch that shades the soil, suppressing weeds and conserving moisture. The difference in root depth ensures that competition for resources is minimal.
Another effective strategy is using companion plants as a “trap crop” to divert pests away from the potatoes. Nasturtiums and some varieties of onions, for example, are highly attractive to certain insects, drawing them away from the main potato plants. Gardeners can then manage the pests concentrated on the trap crop, protecting the potato harvest.
The process of hilling potatoes, which involves mounding soil around the growing stems to encourage tuber formation, must be considered when planting companions. Shallow-rooted companions should be planted far enough away from the main stem to allow for three to four inches of additional soil to be added during the hilling process. This ensures the necessary soil manipulation does not damage the companion plants or their root systems.