Sweet potatoes are propagated using sprouts called “slips,” rather than seeds or root pieces. This method efficiently turns a single tuberous root into multiple new plants for the garden. Slips are small vine cuttings generated by the parent sweet potato, which are then rooted and planted to produce the next season’s harvest.
Sprouting Techniques for Generating Slips
The initial step involves placing a healthy sweet potato in an environment that stimulates sprout development. Two primary methods are used to coax these slips to grow: the water method and the soil bedding method. The water method requires the sweet potato to be partially suspended in a jar of water using toothpicks, ensuring at least half of the tuber is submerged. Change the water every few days to prevent rot, and place the setup in a warm, brightly lit location.
The soil bedding method is often quicker and more reliable. Place the sweet potato horizontally in a shallow tray filled with damp sand or potting soil, covering the tuber about halfway. Keep the container warm (ideally above 75°F) and under bright light or a grow lamp. The soil method produces slips in three to four weeks, while the water method may take four to eight weeks.
Separating and Rooting the New Plant Starts
Once the slips have grown to a length of approximately four to six inches, separate them from the parent sweet potato. Use a clean, sharp cut or gently twist the slip off at its base where it emerges from the tuber. This ensures a clean break and prevents the transfer of potential disease. The parent sweet potato can often remain in place to continue generating additional slips.
The separated slips need to develop a robust root system before planting. Place the cut ends into a jar of fresh water or a small pot of moist potting mix. Keep the slips in a bright location; small white roots should begin to form within one to two weeks. Once a dense cluster of roots has established, the young plants are ready for transition. This transition, known as “hardening off,” involves gradually exposing the starts to outdoor conditions for about a week before final planting.
Cultivating and Harvesting the Sweet Potato Crop
Sweet potatoes thrive in warm conditions and should not be transplanted outdoors until all danger of frost has passed and the soil temperature registers above 60°F. They perform best in loose, well-drained, sandy soil, as heavy clay impedes root expansion. Plant the slips into raised mounds or rows, spaced 12 to 18 inches apart, to ensure proper drainage and space for the vines. Bury each slip deep, up to its top leaves, since new sweet potatoes form at the nodes along the buried stem.
Consistent watering is necessary for the first week after planting to help the slips establish roots. Once established, sweet potatoes are drought-tolerant but benefit from about one inch of water per week. The plants require a balanced nutrient profile, favoring high phosphorus and potassium for root development. Too much nitrogen can lead to excessive vine growth at the expense of the underground crop.
The crop is ready for harvest between 90 and 120 days after planting, usually when the leaves and vine ends begin to turn yellow. Harvest the sweet potatoes before the first hard frost, as cold soil temperatures can damage the roots. After digging, the roots require curing to enhance flavor and storage life. Curing involves holding the sweet potatoes at 80 to 85°F, with 80 to 90% humidity, for four to fourteen days. This process converts starches into sugars and allows the skins to heal, improving storage ability.