Sweet potatoes are propagated from specialized vine cuttings called slips, which are vegetative sprouts emerging from the mature storage root. This method of vegetative reproduction is standard for commercial and home cultivation because it ensures the genetic consistency of the parent plant. Achieving a high yield of uniform roots depends on employing the correct planting technique and depth.
Preparing Sweet Potato Slips for Transplant
Sweet potato slips can be sourced from reputable nurseries or grown at home by sprouting a sweet potato. When slips arrive or are freshly harvested, they are essentially bare stem cuttings and may appear wilted or lack fully developed roots. This condition is normal, and the slips are resilient enough to recover quickly after proper preparation and planting.
To encourage root development before transplanting, slips are often placed in water until small white roots begin to form. This rooting process, while not strictly necessary, helps establish the plant more quickly once it is placed in the soil. Before the final planting, the slips must be gradually introduced to outdoor conditions like direct sun and wind. This process, known as hardening off, involves progressively increasing the time the slips spend outside over about a week.
Selecting the Ideal Planting Environment
Sweet potatoes are a tropical crop. Planting should only occur well after the last expected frost, when the soil has thoroughly warmed. The minimum threshold for planting is a consistent soil temperature of at least 60°F, though many growers recommend waiting until the soil reaches 65°F to 70°F for optimal growth and to prevent the slips from rotting.
The planting location should receive full sunlight, ideally eight to ten hours a day. Sweet potatoes perform best in loose, well-draining soil, such as a sandy loam. Heavy clay soils present a challenge because they can impede root expansion and proper drainage.
To address drainage issues and provide space for root development, the soil should be prepared by forming raised beds or mounds, typically six to eight inches high. This practice allows the soil to warm faster in the spring and makes the eventual harvest easier. Too much nitrogen should be avoided, as it encourages excessive leafy vine growth at the expense of developing the edible storage roots.
Precise Planting Technique and Depth
The depth at which a sweet potato slip is planted is the primary factor influencing the size and quantity of the final harvest. The sweet potato roots form along the buried stem at points called nodes, rather than growing downward from a single root ball. Therefore, the goal is to maximize the length of the stem section that is covered by soil.
Before planting, any leaves on the lower half of the slip should be removed, leaving only the top two or three leaves intact. The slip should then be set deeply into the prepared soil, ensuring that the entire leafless portion of the stem is buried. This planting depth typically means the slip is set about four to six inches deep, depending on the length of the cutting.
The deep planting method encourages multiple nodes along the buried stem to initiate the formation of new tuberous roots. The soil should be firmly but gently pressed around the buried stem to ensure good soil-to-root contact. Proper spacing is also important, with slips generally spaced 12 to 18 inches apart within the row. Rows should be separated by at least three feet to allow the vigorous vines ample space to sprawl.
Initial Care for Successful Establishment
Newly planted slips require immediate and thorough watering to settle the soil around the roots and minimize transplant shock. The initial watering should be deep enough to completely soak the planting mound or raised bed. It is common for the leaves on the young slips to wilt dramatically after planting, especially if the weather is sunny and hot.
To help the slips recover, consistent moisture is necessary for the first week to ten days following transplanting. During periods of intense sun or high heat, temporary shading, such as a row cover or cardboard, can be used for the first few days to protect the tender leaves. After this initial establishment period, sweet potatoes are quite drought-tolerant.
Weed control is also important early in the season before the vines begin to grow rapidly. Removing weeds by hand or with shallow cultivation prevents competition for water and nutrients. Once the sweet potato vines begin to spread and cover the ground, they naturally shade out most emerging weeds, reducing the need for further intervention.