Sweet potato (\(Ipomoea\ batatas\)) is a vigorous, heat-loving vining crop cultivated for its edible tuberous roots and sprawling foliage. Grown as an annual in most climates, it requires ample space and a long, warm growing season for a successful harvest. Companion planting is the practice of growing different crops in close proximity to promote a healthier garden ecosystem. This technique can enhance productivity by naturally controlling pests and improving the health of the soil.
Plants That Offer Protection Against Pests
Aromatic plants can be strategically placed near sweet potatoes to confuse or repel common insect pests that target the foliage and roots. Alliums, such as chives and garlic, emit potent sulfur compounds that create an offensive odor barrier against major threats like the sweet potato weevil. This strong scent masks the chemical signals pests use to locate the plants, disrupting their feeding and reproduction cycles.
Flowering plants like Marigolds, particularly the French variety, deter pests within the soil. They release chemicals from their roots that suppress nematode populations, which damage the root system and reduce tuber formation. Nasturtiums serve a different function, acting as a “trap crop” by drawing aphids and flea beetles to their own foliage, keeping these leaf-chewing insects away from the sweet potato vines.
Herbs, including dill and summer savory, contribute to pest management by attracting beneficial insects. Dill flowers attract parasitic wasps and hoverflies, which are natural predators of aphids and other soft-bodied pests. Sweet alyssum can be planted as a low-growing border to attract these same beneficial insects, creating a protective perimeter. This biological control method reduces the reliance on chemical interventions.
Improving Soil Quality and Managing Weeds
Sweet potatoes are heavy feeders that draw substantial nutrients from the soil, especially nitrogen to fuel extensive vine growth. Low-growing legumes, such as bush beans or peas, work in partnership by fixing atmospheric nitrogen into the soil through a symbiotic relationship with rhizobia bacteria in their root nodules. This process replenishes the soil’s nitrogen supply, ensuring the main crop has a steady source of this nutrient.
The sprawling sweet potato vines function as an effective living mulch, shading the soil surface and suppressing weed growth. This dense cover conserves soil moisture by reducing evaporation and keeps the soil temperature cooler in hot climates. Shallow-rooted crops like radishes can be sown directly into the patch before the vines fully spread. Their quick taproots break up compacted soil, improving aeration and making it easier for the developing tubers to expand.
Spinach and various low-growing lettuces can also serve as a temporary ground cover early in the season. These plants provide a layer of protection that prevents soil erosion and suppresses weed competition until the sweet potato vines take over. Their shallow roots do not compete significantly with the deeper-growing sweet potato tubers, allowing them to coexist productively in the same planting space.
Important Plants to Keep Separate
Not all plants are beneficial companions; some actively hinder the growth and health of sweet potatoes due to direct competition or shared vulnerabilities. Large, aggressive vining crops like squash and pumpkins should not be planted nearby. Both the sweet potato and the squash are heavy feeders, and their extensive root systems will compete for the same limited resources, leading to reduced yields for both crops.
Tomatoes and Sunflowers pose a risk due to shared disease susceptibility and allelopathic effects. Tomatoes belong to the nightshade family and are prone to the same blights and pests as the sweet potato, increasing the likelihood of disease transmission. Sunflowers can stunt the growth of nearby sweet potatoes by releasing chemical compounds into the soil that inhibit the growth of other plants.
Other root vegetables that develop large, deep roots, such as parsnips or standard potatoes, compete directly with the sweet potato for subterranean space. While small, fast-maturing root crops are acceptable, those with a similar growth habit interfere with the formation and size of the sweet potato’s tubers. Competitive plants should be situated separately to ensure the sweet potatoes have adequate resources to thrive.