Companion planting is a gardening strategy where specific crops are placed near each other to create a mutually beneficial environment. This technique can help repel pests, attract helpful insects, and improve soil health and nutrient uptake. For a vigorous crop like the sweet potato, choosing the right garden neighbors is key to maximizing the harvest. Since sweet potatoes spread widely and require specific conditions for their underground storage roots to develop, selecting a compatible planting partner is important for a successful growing season.
Identifying the Worst Neighbors
Several popular garden plants should be kept at a distance from sweet potatoes to prevent resource conflicts and the spread of problems. The sprawling, heavy-feeding nature of Cucurbitaceae family members makes them poor companions. These include winter squash, summer squash, pumpkins, cantaloupe, and watermelon, which aggressively compete for space and nutrients.
Another group to avoid is tall, dominant plants that create extensive shade, such as sunflowers and corn. Sunflowers may also increase the risk of potato blight, a fungal disease that can affect sweet potatoes. Tomatoes are problematic neighbors, as they share susceptibility to common diseases and attract pests like aphids and whiteflies that can move to the sweet potato vines. Finally, avoid planting other root vegetables, such as potatoes or carrots, too close, as they compete directly for subterranean space and soil nutrients.
Understanding the Causes of Incompatibility
The conflicts between sweet potatoes and these incompatible plants stem from three primary biological and physical mechanisms. Intense resource competition is the first, as sweet potatoes are heavy feeders that require continuous nutrients and water to swell their storage roots. Plants like squash and tomatoes have similarly high appetites for nutrients such as phosphorus and nitrogen, depleting the available supply faster than the sweet potato can tolerate.
The second major issue is the sharing of pests and diseases, which increases the likelihood of a widespread crop failure. Tomatoes, for example, are susceptible to blight and share pests like flea beetles and aphids with sweet potatoes, effectively creating a pest bridge. Certain plants, including some morning glories and other Ipomoea species, act as alternate hosts for the devastating sweet potato weevil, the most serious pest of the crop.
The third mechanism is physical interference, where the growth habit of one plant physically inhibits the sweet potato’s development. Tall plants like corn and sunflowers can cast excessive shade over the sprawling sweet potato vines, which require full sun to produce energy for tuber formation. Similarly, the aggressive, broad-leafed spread of pumpkins and squash can physically dominate the ground, preventing the sweet potato vines from rooting along the nodes to maximize growth and yield.
Ideal Sweet Potato Companions
Selecting the right companions can actively support the sweet potato crop by deterring pests and enriching the soil. Legumes, specifically bush beans and pole beans, are excellent partners because they host nitrogen-fixing bacteria in their root nodules. This process releases nitrogen into the soil, an element the sweet potato uses heavily for its vigorous vine growth.
Aromatic herbs and flowers offer a form of natural pest control by confusing or repelling harmful insects. Herbs that emit scents to mask the presence of sweet potato plants include:
- Dill
- Thyme
- Oregano
- Summer savory
Summer savory is noted for its ability to deter the weevil, a significant threat to the tubers.
Flowers like marigolds and sweet alyssum also provide substantial benefits. Marigolds are known to suppress nematodes, microscopic roundworms that can damage the root system, while their strong smell repels other pests. Sweet alyssum acts as a living mulch, covering the ground to suppress weeds, and its small flowers attract beneficial insects like parasitic wasps and hoverflies, which prey on common pests such as aphids.