Sweet potato cultivation requires a distinction between initial preparation and mid-season maintenance. Sweet potato slips are typically planted into pre-formed mounds or raised rows, but unlike true potatoes, they do not require additional hilling throughout the growing season. The initial construction of a raised bed structure is a foundational element of successful cultivation for these warm-weather crops. This practice addresses specific needs related to soil temperature and water management, which are paramount for sweet potato development. Gardeners should focus on creating the right environment at planting time rather than adding soil later.
Initial Planting Structure: Preparing Raised Beds
Sweet potatoes require loose, well-draining soil and significant warmth to thrive. Planting them in raised structures helps the soil warm up faster in the spring, allowing planting to occur earlier than in flat garden beds. This elevated structure also prevents water from collecting around the developing roots, minimizing the risk of rot in heavier or clay soils. Sweet potatoes dislike consistently waterlogged conditions.
The recommended height for these initial mounds or ridges is generally between 6 and 10 inches high. Creating this loose, deep structure provides ample space for the storage roots to expand without becoming stunted or misshapen. Slips, which are rooted sprouts, are planted into the top of these prepared hills. Spacing the slips 12 to 18 inches apart within the mound ensures each plant has sufficient room and access to nutrients.
Hilling Versus Mounding: Understanding the Difference
Confusion between mounding and hilling arises from comparing sweet potatoes to white potatoes. The sweet potato is botanically a storage root—an enlarged lateral root, not a stem tuber. The edible portion develops downward from the planted slip, deep within the original soil structure.
In contrast, white potatoes are tubers, which are modified underground stems. These tubers develop upward and close to the soil surface. Exposure to light causes them to turn green and produce toxins. Hilling—the act of adding soil to the base of the plant during the growing season—is necessary for white potatoes to cover the developing tubers and prevent this greening.
Since sweet potatoes are storage roots, they do not face the same greening issue, making mid-season hilling unnecessary. Adding extra soil to the established plants may hinder the development of the primary storage roots by encouraging the plant to put energy into new stem growth or above-ground rooting. The initial mound provides the necessary loose soil for root formation, and no further soil addition is required.
Managing Sweet Potato Vine Growth
Once the slips are established in the initial mounds, the primary focus shifts to managing the extensive vine growth. Sweet potatoes are vigorous vining plants that spread quickly, often covering the ground within six weeks. The long runners can develop roots at the nodes where they touch the soil, especially in warm, moist conditions.
When the vines root at these secondary points, the plant’s energy is diverted from the main storage roots to establish new, smaller root systems. To maximize the harvest of larger sweet potatoes, gardeners can periodically “lift” the vines. Gently detaching the vines from the soil every few weeks prevents them from rooting and redirects the plant’s energy back toward the primary storage roots forming beneath the initial mound.