Sweet potatoes are not grown from a seed or a planted tuber like a regular potato; instead, they are propagated from rooted cuttings called “slips.” Growing sweet potatoes from slips ensures the resulting plants are clones of the parent and are ready for warm-weather planting. Starting your own slips typically begins 8 to 12 weeks before your last expected frost date.
Preparing the Sweet Potato for Sprouting
Select a healthy sweet potato to serve as the “mother” plant. Choose a potato that is firm, unblemished, and ideally organic or untreated, as conventional varieties may contain sprout inhibitors. Avoid roots that appear soft, shriveled, or have been refrigerated, as cold temperatures inhibit sprouting. You can use a whole potato, or cut a large potato in half lengthwise to increase the surface area for sprouting.
The setup requires a glass jar or cup, water, and three to four wooden toothpicks. Ensure the potato is clean. If you cut the potato, allow the surface to dry for a few hours to form a protective layer, which minimizes the risk of the mother potato rotting once placed in water.
Step-by-Step Guide to Sprouting Slips
Insert three or four toothpicks around the midsection of the sweet potato to suspend it over the mouth of the jar. The blunt, or stem, end of the potato should face down into the water. Fill the jar until the bottom half of the sweet potato is submerged, maintaining a consistent water level.
Place the setup in a warm, bright location, such as a sunny kitchen windowsill. Sweet potatoes require warmth to break dormancy, with ideal temperatures ranging between 75°F and 85°F. Small roots should emerge from the submerged end within a few days to a week. The leafy sprouts, or slips, will begin to emerge from the eyes on the potato’s surface over the next three to six weeks.
The water must be changed every two to three days to maintain oxygen levels and prevent mold or bacteria growth, which can cause the mother potato to rot. The slips are ready when they reach a usable size, usually four to six inches long, with several developed leaves.
Harvesting and Rooting the Sprouts
Once the slips reach four to six inches, carefully detach them from the mother potato. You can gently twist the slip off at its base or use a clean, sharp knife to cut it away. Harvest the slip without taking any of the mother potato’s flesh, as this part contains growth inhibitors that can slow the slip’s rooting process.
Place the base of the separated slips into a fresh jar of water, ensuring only the bottom inch or two of the stem is submerged, with the leaves remaining above the water line. The submerged stem will begin to develop fine, white roots, typically within one to two weeks.
Continue to change the water every few days while the slips are rooting to keep the environment clean and oxygenated. The slips are ready for transplanting when these new roots are numerous and about an inch or two in length.
Troubleshooting Common Sprouting Problems
A common issue is the failure of the sweet potato to sprout after several weeks in water. This often results from cold temperatures, as sweet potatoes will not sprout reliably below 70°F, or from using potatoes treated with sprout-inhibiting chemicals. Moving the jar to a warmer spot or using a heat mat can correct a temperature-related delay in sprouting.
Another frequent problem is the mother potato developing a slimy film or beginning to rot. This is usually caused by insufficient oxygen or bacterial growth in the water. Changing the water every other day is the primary solution, and adding a drop of hydrogen peroxide to the fresh water can help inhibit microbial growth. If the slips appear pale and spindly, known as “leggy” growth, it indicates they are not receiving enough light. Moving the setup to a location with more intense direct sunlight will help the slips develop stronger, greener stems and leaves.