Sprouting a sweet potato in water is a popular method for home gardeners to prepare for planting or to cultivate a decorative houseplant. This process encourages the tuber to produce new shoots, known as slips, which are used to grow new sweet potato plants. Understanding the correct orientation of the sweet potato is the most important step for successful sprouting.
Identifying the Correct Orientation
The sweet potato, a storage root, has a natural polarity determining where roots and shoots will emerge. Successful sprouting requires submerging the rooting end to encourage water absorption and root development. The opposite end, the sprouting end, must remain above the water line to produce the desired slips.
Differentiating between these two ends can be challenging, as the sweet potato’s shape varies widely by variety. A reliable indicator is the presence of small, hairlike roots visible on the skin; these are concentrated at the rooting end. If roots are absent, the rooting end is often more tapered and pointy. The sprouting end, where the tuber was attached to the original vine, tends to be blunter and may have a denser concentration of nodes or “eyes.”
The sprouting end must be exposed to air and light for shoot development. Placing the rooting end downward allows the tuber to draw moisture efficiently, fueling the growth of water roots below and slips above. If the sweet potato is symmetrical and the ends are indistinguishable, some gardeners lay it horizontally. However, vertical placement is usually more effective for concentrating growth and conserving space.
Setting Up the Sprouting Container
Once the correct orientation is determined, prepare the sweet potato for suspension in a water-filled container. A clear glass jar is ideal because it allows easy monitoring of the water level and root development. To suspend the sweet potato with the rooting end partially submerged, insert three or four wooden toothpicks horizontally around the middle of the tuber.
Push the toothpicks in far enough to provide stability, allowing them to rest on the container’s rim. Maintain the water level so that only the bottom third to half of the rooting end is submerged, leaving the sprouting end exposed. Submerging the entire tuber is not recommended, as the top needs to be out of the water for oxygen exchange and shoot growth.
Place the container in a warm location, ideally where temperatures are consistently 75 to 80 degrees Fahrenheit. Bright, indirect sunlight from a sunny window is sufficient to initiate growth. A warmer spot, such as on top of a refrigerator, can help speed up the process. Within a few days, small white roots should begin to emerge from the submerged end, followed by shoots appearing on the top within a few weeks.
Caring for the Sprout and Harvesting Slips
Ongoing maintenance is required to ensure the sweet potato remains healthy and productive while generating slips. The water in the container needs to be changed regularly, about once a week, to prevent the growth of mold, bacteria, or algae that can harm the developing roots. When changing the water, ensure the level is consistently maintained to keep the bottom portion of the tuber submerged.
The slips need to reach a suitable size before they can be harvested for planting. They are ready to be removed when they are between four and six inches long and have several established leaves. To harvest, gently twist or snap the slips off at the point where they emerge from the sweet potato. Ensure the break is clean and leaves a small base.
After removal, these slips are not planted directly into the garden. They are first placed in a separate glass of water to encourage new root formation. This secondary rooting step usually takes only a few days, during which time the slip develops its own robust root system. Once the new roots are several inches long, the rooted slips are ready to be transferred to soil in the garden. The original sweet potato can be left in the water to continue producing more slips.