You may have noticed that if you leave them long enough, sweet potatoes start to grow. If you were to plant the tuber, you would get a sweet potato plant. Unfortunately, if you plant the tuber as is, it will not produce more tubers. And if you are going to bother growing a sweet potato plant, which will like lots of sun, water, and food, you will want to get tubers.
To get a sweet potato start that will produce numerous tubers, you will want to make slips.
Select a healthy tuber from the grocery store. Cut the tuber in half and place in a jar with the cut side face down, half submerged in water. You might use toothpicks to secure the tuber in place. Place in the sunniest window you can find.
In a week or so, buds will appear (sometimes it takes longer—some varieties of sweet potato are quicker than others). Let these buds grow and produce a few leaves. Roots may also appear where these buds emerge from the tuber.
When these buds have about three leaves, or just look vigorous, use a razor blade to slice them away from the tuber. Place the buds in water with leaves out in the air. Keep watered and wait for roots to grow. These are your sweet potato slips.
Once the slips have put out a good amount of roots and look vigorous, you can plant them outside. Plant at least 1½ feet apart and keep very well watered. If they were not in very much sun, you might give them some shade at first, until they are established.
Keep in the ground until just before a frost (a hard frost will damage tubers). You can push more dirt up and around the base of plants as they grow to encourage more tuber development. When you harvest them, dry them out in the open air (in a shady spot) to cure them.
If you want to grow more unusual varieties of sweet potatoes, besides what are available in grocery stores, try Duck Creek Farms. They sell rooted slips that you can plant immediately. ✜