Growing a sweet potato in water is a method used to produce “slips,” which are the vegetative sprouts necessary for propagation. The sweet potato is a tuberous root that stores energy, and placing it in water stimulates it to initiate new growth. This simple, water-based technique generates small, rooted plants that can be used to start a garden patch or grown indoors as a decorative, vining houseplant. The goal is to encourage the tuber to use its stored starches to fuel the development of stems and leaves, which are then harvested and rooted independently.
Choosing the Right Sweet Potato
The success of generating slips begins with selecting a high-quality tuber. Choose sweet potatoes labeled as organic, as conventionally grown tubers are sometimes treated with growth-inhibiting chemicals that prevent sprouting. The ideal potato should be firm, free of soft spots, mold, or significant blemishes that could introduce rot into the water container. True sweet potatoes (Ipomoea batatas) are distinct from yams and are the variety that readily produces slips.
A healthy tuber will have small, visible indentations or “eyes” ready to sprout. If the sweet potato has a tapered end and a blunter end, the blunter, or stem, end should generally be placed upward, as it is more likely to produce shoots. Cutting a large potato in half can increase the surface area for sprouting, but a whole, firm potato works just as well and is less prone to rot.
Setting Up the Water Container
The sweet potato must be suspended so that only a portion is submerged in water. Insert three to four toothpicks equidistantly around the middle of the tuber to act as supports. These toothpicks rest on the rim of a narrow-mouthed jar or glass, holding the potato in place. Adjust the water level so that roughly the bottom one-third to one-half of the potato is consistently submerged.
If the potato has a noticeable tapered end, position the blunter end upward. Place the container in a location that receives bright light but is shielded from direct afternoon sun, such as a warm windowsill. Maintaining a consistently warm environment will accelerate the sprouting process.
Ongoing Care and Sprout Development
Consistent water maintenance is necessary to prevent the growth of mold, bacteria, and algae, which can cause the sweet potato to rot. Completely replace the water every four to seven days to keep the environment fresh and oxygenated. This replacement also allows for a quick inspection of the submerged portion for any signs of decay or cloudiness.
With adequate warmth and light, the first sign of activity will usually be the emergence of fine, white roots from the submerged portion of the tuber, which may appear within one to two weeks. Shoot development, known as “slips,” will follow, often taking between two and four weeks to appear from the upper surface of the potato. The sweet potato utilizes its stored carbohydrates and nutrients to fuel this new stem and leaf growth. Slips may emerge from both the submerged section and the top, exposed half.
Separating and Preparing the Slips
Slips are ready for harvest when they reach a length of approximately four to six inches, usually six to eight weeks after setup. The sprouts must be removed from the parent potato before planting; planting the entire tuber results in undeveloped roots. To harvest, gently twist the slip off at its base, or use a clean, sharp knife to cut it away without taking a piece of the tuber.
After separation, place the individual slips into a new container of clean water to encourage the development of their own root systems. This curing process is necessary, as the freshly cut slips need time to form robust, independent roots before they can be successfully planted in soil. New roots should appear quickly, often within a few days. The slips are ready for a permanent location once the roots are several inches long, and the parent sweet potato can continue producing multiple batches of slips over several weeks.