Determine the top and bottom of a sweet potato. Most sweet potatoes have a rounded, fatter end and a skinnier, pointed end. The pointed end produces roots, while the fatter ends sprouts leaves.
Fill a tall glass jar with water. This is what you will put your sweet potato in.
Insert three or four toothpicks in a radius around the middle or upper third of the sweet potato. These will be used to prop up the sweet potato on the jar.
Place the sweet potato in the jar of water, with the pointed end down and the upper, fatter parts exposed to the air.
Place the jar in a warm, sunny location, like a south-facing window or the top of the refrigerator. Keep the jar filled with water. The sweet potato should begin to sprout roots, stems and leaves within one to three weeks.
Transfer the sprouted sweet potato to a container filled with potting mix to grow as a houseplant. You can also plant it outside in the garden in the spring after the danger of frost has passed. The roots and stem of a newly sprouted sweet potato are fragile, so handle them carefully. Sweet potatoes may also be grown in water for several weeks if necessary.
Keep indoor sweet potato vines in a location with as much sun as possible. Outdoor sweet potato plants should be grown in the sunniest part of the garden, in the area with the most protection from frost.
Water your sweet potato plant regularly to keep the leaves from wilting. Outdoor sweet potatoes should be watered in the very early morning, right around dawn, so the water can soak in before the heat of the day begins.
Apply compost or all-purpose fertilizer once a month to your sweet potato plants. The nutrients provided will allow them to grow well all year long.