What you need: pre-sprouting sweet potato (some food stores treat the potatoes with heat so they won't sprout; to see if you have a sprouter enclose a sweet potato in a paper bag and sprouts should appear in a short amount of time), glass jar, water, knife, and toothpicks (optional)
There are 2 methods of growing the vine: Method #1- We cut the bottom 1/3 off the potato so it would fit snugly in a little mason jar. Only about a 1/2 inch of the potato flesh is submerged into the water; this is all it takes to grow a beautiful vine. Method #2- don't cut the potato; poke 4 toothpicks into the sides of the potato, about 2 or 3 inches from the bottom. A lot more of the potato will be submerged into the water this way. Then balance the potato on top of the jar (which can be quite a balancing act). Either method works fine.
See how only a little bit of our potato is actually under water, only about 1/2 inch.
Keep the water clean by changing the water daily or the potato can cause quite a stink, especially if a lot of the potato is submerged!
After a few days the roots will start forming; then many roots will form daily! After a month take the potato out of the water and plant it in potting soil. This makes a beautiful houseplant. Tie the vines to string and let it grow around a windowpane for a really pretty look. I also have a post on how to grow potatoes indoors. Have a look at Pink and Green Mama's method of growing the sweet potato.
Just a little note about what I'm up to right now, I am working on 2 posts involving those lawn plants some people refer to as weeds (clover and plantain). I have some easy medicine making to share with you. I am also working on a PTOE post on nitrogen. I should have these posted in the next week.
Enjoy!