The process of rooting a sweet potato in water is a common technique used either to create an attractive, fast-growing houseplant or, more practically, to generate “slips,” which are the vegetative cuttings used to start a sweet potato crop. Sweet potatoes, botanically known as Ipomoea batatas, are not true potatoes but rather a tuberous root from the morning glory family. Unlike regular potatoes, they are not grown from the root itself, but from these rooted sprouts or slips, making the water-rooting method a necessary first step for many gardeners.
Selecting and Preparing the Sweet Potato
Select a firm, unblemished tuber free of soft spots or mold, as a damaged surface can easily rot in water. It is highly recommended to use an organic sweet potato, as non-organic tubers are often treated with a sprout inhibitor.
Before setting up, the sweet potato needs to be thoroughly washed and its orientation determined. Every sweet potato has a stem end and a root end; the root end is the one that should be submerged in water. This end is typically the pointier or more tapered side, and it may sometimes show fine, hair-like root remnants. The stem end, which produces the leafy slips, is usually blunter or more rounded.
Gather a glass jar or another container wide enough to hold the potato but narrow enough for the support mechanism to rest on the rim. The water used should be room temperature, and while tap water is acceptable, some people prefer filtered water.
Step-by-Step Guide to Water Rooting
To achieve the setup, insert three to four wooden toothpicks evenly around the middle circumference of the sweet potato. Place these toothpicks about halfway up the tuber, creating a tripod or quad-pod support structure.
Carefully lower the sweet potato into the container, allowing the toothpicks to rest on the rim of the jar. The pointed, root-producing end should be facing down into the vessel. Add water until roughly the bottom third to half of the sweet potato is covered.
This setup ensures that the part of the tuber responsible for producing roots is in contact with water, while the upper half, where the leafy slips will emerge, remains exposed to the air. Initial placement of the container should be in a warm location, ideally with temperatures around 75 to 80°F (24 to 27°C), which encourages the quickest initial growth.
Essential Care During the Rooting Process
The water in the container must be changed every four to seven days to prevent it from becoming stagnant, which can encourage mold, bacteria, or fungal growth that would cause the potato to rot. If the water appears cloudy or develops an odor, it should be replaced immediately.
Place the rooting setup in a location that receives bright, indirect light. While sweet potatoes thrive in warmth, direct, intense sunlight can cause the water to heat up too quickly or encourage excessive algae growth. Roots typically begin to emerge from the submerged end within a few weeks, followed shortly by the development of green shoots, or slips, from the top of the tuber.
The entire process, from setup to having harvestable slips, generally takes between six and eight weeks. If no progress is seen after four weeks, the potato may have been treated with an inhibitor and may need to be replaced.
Harvesting Slips and Planting
The leafy sprouts, or slips, are ready for harvest once they reach a length of approximately four to six inches. To remove them, gently twist or carefully cut the slip away from the tuber at its base, taking care not to damage the emerging roots of the slip.
Once harvested, the slips must develop their own dedicated root systems before they can be planted in soil. Stand the cut end of each slip in a separate jar of fresh water, ensuring only the bottom inch or two is submerged. This encourages the rapid formation of adventitious roots from the nodes.
Within one to two weeks, the slips will develop a network of white roots that are one to two inches long. At this stage, the slips can be planted directly into the garden soil, provided the outdoor soil temperature is consistently above 60°F (15°C) and all danger of frost has passed. Plant the slips deep enough to cover the new roots and the stem up to the first set of leaves.