Sweet potatoes (Ipomoea batatas), the official state vegetable, are a warm-season crop. North Carolina produces the majority of the nation’s supply, making them ideal for home gardens across the region. Unlike standard potatoes, sweet potatoes are tropical root vegetables that require specific conditions to thrive, primarily heat and a long growing season. This guide details how to cultivate this rewarding crop in North Carolina’s unique climate and soil.
Site Selection and Soil Preparation in NC
Sweet potatoes require a location that receives full sun, as the heat is necessary for the plant to develop its edible storage roots. The ideal soil is well-drained, sandy loam, which is common in many parts of the state, especially the Coastal Plain where commercial production is concentrated. Heavy clay soils or those with poor drainage can lead to misshapen roots, so soil structure is more important than fertility.
The soil should be slightly acidic, with an optimal pH range of 5.8 to 6.2. Gardeners should conduct a soil test before planting and adjust the pH with lime if necessary. Sweet potatoes perform poorly in overly rich, nitrogen-heavy soil. Excessive nitrogen encourages lush, sprawling vines at the expense of root development. Prepare the bed by tilling the soil deeply to loosen it. Planting on raised mounds or ridges greatly improves drainage and helps the soil warm up quickly in the spring.
Sourcing and Planting Sweet Potato Slips
Sweet potatoes are propagated from slips, which are vine cuttings or sprouts grown from a mature sweet potato, not from seeds. Purchasing certified, weevil-free slips is the best way to ensure a healthy start and prevent the introduction of pests. Planting timing is crucial in North Carolina due to the crop’s sensitivity to cold.
Planting should occur after all danger of frost has passed, typically from late May to early June, when the soil temperature consistently reaches at least 60°F. Planting when the ground is still cool will stunt growth and result in a poor harvest. Slips should be planted deep enough so the stem is buried up to the top leaves, ensuring several nodes are below the soil surface where roots will form.
Space plants 12 to 18 inches apart, with rows three to four feet apart to accommodate the sprawling vines. Immediately after transplanting, water the slips thoroughly to help settle the soil and reduce transplant shock.
Essential Care and Pest Management
Once established, sweet potatoes are relatively drought-tolerant, but they require consistent moisture, especially during dry periods in the hot North Carolina summer. Watering is most important in the first few weeks after planting and again when the storage roots begin to swell. Applying a layer of mulch, such as straw or black plastic, helps suppress weeds and maintain soil moisture and warmth.
Weed control is important during the first month, as young sweet potato plants cannot compete with aggressive weeds like Palmer amaranth. A common practice is “vine turning,” where the long vines are periodically lifted and moved. This prevents them from rooting at the nodes, which would otherwise produce many small, unusable tubers instead of channeling energy into the main roots.
The sweet potato weevil is a significant regional pest, though the North Carolina Department of Agriculture and Consumer Services actively monitors and quarantines against it. Home gardeners prevent weevil issues by only planting certified slips and practicing crop rotation, avoiding planting sweet potatoes in the same spot more than once every three years. Flea beetles are another common pest, which can be managed by planting resistant varieties like ‘Jewel’ or ‘Centennial’.
Harvesting and Curing for Storage
Sweet potato harvest typically occurs 90 to 120 days after planting, usually in late summer or early fall. The first sign the crop is ready is when the leaves and vine tips begin to yellow, indicating the plant is slowing its growth. Harvest the entire crop before the first hard frost, as cold temperatures can damage the tubers and compromise their storage life.
To harvest, use a garden fork to loosen the soil, starting well away from the central vine to avoid puncturing the delicate tubers. Sweet potatoes have thin skin that is easily bruised or scraped, requiring careful digging and handling to prevent wounds that can lead to decay. Once dug, brush off any loose soil but do not wash the roots.
The most important post-harvest step is curing, which improves flavor and storage life. Curing involves holding the unwashed tubers at a high temperature (ideally 85°F) and high humidity (85 to 95 percent) for four to fourteen days. This process converts starches into sweet sugars and allows minor scrapes to form a protective cork layer. After curing, store the roots in a cool, dark, and dry area, maintaining a temperature between 55°F and 60°F for long-term keeping.