Sweet potato cultivation relies on “slips,” which are rooted sprouts developing from the mature tuberous root. Unlike traditional potatoes, sweet potatoes require these young plant starts to successfully grow a new crop. Saving slips for the following season involves keeping the parent sweet potato, or “seed potato,” dormant and viable throughout the cold winter months. This process involves a three-step cycle: a high-heat healing process, a cool-temperature dormancy period, and a final re-awakening to generate new slips in the spring.
Preparing Sweet Potatoes for Storage (Curing)
Curing is the post-harvest step, serving the dual purpose of healing physical wounds and improving the root’s flavor profile. This process allows minor cuts and bruises sustained during harvest to heal by forming a corky, protective layer of wound tissue. Healing these injuries prevents the entry of disease-causing organisms and significantly reduces water loss, which is necessary for long-term storage.
The ideal environment for curing requires high heat and high humidity, typically maintained for 4 to 14 days, depending on the ambient temperature. Sweet potatoes must be held at a temperature between 80 and 85°F (27–29°C) with a relative humidity of 80 to 90%. Home growers can recreate these conditions by placing the roots near a furnace vent or on a seedling heat mat covered by a plastic sheet to trap moisture.
This controlled environment also triggers an internal biochemical change, converting starches within the root into natural sugars, which intensifies the characteristic sweetness and flavor. Curing must be completed immediately after harvest, as delaying this step compromises the root’s ability to heal and store properly.
Maintaining Seed Potato Viability Through Winter
Once curing is complete, seed potatoes must transition to a cooler, long-term storage environment to maintain dormancy. The temperature is precisely managed, ideally maintained between 55 and 60°F (13–16°C). Storing roots above 65°F encourages premature sprouting, while temperatures below 50°F cause chilling injury.
Chilling injury manifests as internal discoloration, such as a brown or black tint, resulting in off-flavors and hard areas in the root. Sweet potatoes should never be refrigerated. The storage area should maintain a high relative humidity, preferably around 85 to 90%, to prevent shriveling.
The roots should be stored in materials that allow for adequate airflow, such as cardboard boxes, wooden crates, or newspaper wrapping. Placing the cured roots in a cool, dark location, like an insulated basement or a root cellar, helps them remain dormant until spring. Proper ventilation is beneficial, as it minimizes the risk of spoilage.
Generating New Slips for Spring Planting
The final step is awakening the dormant seed potatoes in late winter or early spring to produce new slips. This process should start four to six weeks before the last expected frost date, allowing time for the slips to grow and root. The seed potatoes are brought into a warm environment with bright light to stimulate sprout growth.
There are two methods for bedding the tubers. The traditional water method involves suspending a sweet potato halfway in a jar of water using toothpicks, allowing it to root and sprout. Alternatively, the soil or sand bedding method involves laying the tuber horizontally and half-burying it in a container filled with a moist growing medium.
Warmth accelerates slip production, with a temperature near 80°F being highly effective. Once the slips reach about 5 to 6 inches in length, they are ready for harvest.
Gently snap or cut the slip from the mother potato, rather than pulling it, to avoid transmitting diseases to the new plant. The harvested slips should be placed in a jar of water for a few days to develop root systems before being transplanted into the garden after the soil has warmed.