Sweet potato slips are the vegetative shoots or cuttings grown from the mature tuber, serving as the planting material for a new crop of Ipomoea batatas. Planting a whole sweet potato tuber directly into the garden often results in a poor yield because the energy is diffused across too many competing sprouts. Since sweet potatoes rarely produce seeds that grow true to the parent plant, this asexual propagation method is the standard practice for home gardeners. Creating these small, rooted plantlets transforms a single tuber into multiple productive plants.
Selecting the Tuber and Timing the Process
The process starts with selecting the right mother tuber, which should ideally be certified disease-free or organic. Conventionally grown sweet potatoes are sometimes treated with sprout inhibitors during storage, preventing them from producing slips. Choosing an organic or locally sourced, cured variety ensures a higher likelihood of successful sprouting. A single healthy tuber can produce several dozen slips, depending on the variety and propagation method used.
Initiate the slip-making process approximately six to eight weeks before the intended outdoor planting date. Sweet potatoes are a tropical crop requiring warm soil, so they should only be transplanted after all danger of frost has passed. This early indoor start provides enough time for the slips to grow to a transplantable size of four to six inches. Starting too late may result in small, weak plants that struggle to establish themselves outside.
Step-by-Step Water Propagation Method
The water method is a common technique for generating sweet potato slips indoors, relying on the tuber’s stored energy and moisture. Begin by thoroughly cleaning the sweet potato. If the tuber is large, cut it into two or three substantial pieces to maximize the surface area for sprouting. Insert three to four wooden toothpicks around the middle of each section to support the tuber in a glass jar or container.
Place the tuber blunt end down, submerged about halfway in the water, with the toothpicks resting on the container rim. Position the setup in a location that receives bright light and remains consistently warm, such as a sunny windowsill. To prevent mold or bacteria growth, which can cause the tuber to rot, the water must be changed every few days. Within three to six weeks, small shoots (slips) will begin to emerge from the sweet potato.
Alternative Propagation in Soil
An alternative method, often preferred for producing a larger quantity of slips, involves propagating the tubers directly in a moist soil medium. This technique utilizes a shallow tray filled with a mix of sand, peat, or a standard potting mix. Lay the whole or cut sweet potatoes horizontally on top of the medium, then cover them lightly with about one to two inches of the soil mix.
Maintaining optimal warmth is necessary for this method, with the ideal temperature range being 75°F to 85°F. Gardeners often use a heating mat beneath the tray to ensure the high soil temperature required for rapid slip development. The medium must be kept evenly moist, mimicking the humid conditions sweet potatoes favor. A benefit of this soil method is that emerging slips often develop stronger initial root systems while still attached to the mother tuber.
Preparing Slips for Planting
Once the shoots reach a length of four to six inches, they are ready to be harvested from the mother tuber. Remove the slips by gently snapping or twisting them off at the base, or by cutting them with a clean blade. Leave any small root nubs behind on the slip, as these will quickly develop into a robust root system.
After harvesting, the slips must be rooted before they can be planted in the garden. This involves placing the cuttings in clean water for one to two weeks to produce a dense network of roots. Once the slips have established a strong root system, they need to be gradually acclimated to outdoor conditions through a process called hardening off. This involves exposing them to increasing periods of direct sun and wind over several days before permanent transplanting. Final planting should only occur when the soil temperature consistently registers above 60°F, ensuring the young plants do not suffer from cold shock.