Having never had success with sweet potatoes and gleaning information from the internet pages, I wanted to share some refinements I was inspired to this year.
The growing of slips can be done by using even the chemical retarded potatoes from the grocery store as God basically put the thought in my mind, "If you wash fruits and vegetables...why not wash sweet potatoes?"
I did this with some liquid soap and have shoots starting to appear on the 2 potatoes I have in jars. (For those unfamiliar, you simply place the sweet potatoe half way into a jar of water (non chlorine worked faster), suspended by toothpicks stuck in the sides of the potatoe and in about a week roots will appear, followed by little sprouts breaking forth.)
Since I didn't want to go up and down to my cellar as the instructions were for placing them on a hot water heater, I put mine on my gas stove top by the pilot lights. That makes the difference in they need that kind of warmth to start. You simply then just keep adding water to the jar or old plastic cottage cheese container you have them suspended in.
It appears you can slow down "growth" once they are sprouted by having them in a more cool place, so that gives some leeway in not having run away vines sprawling all over.
My plan is to twist the slips off when they get 8 to 12 inches, place them into a potting soil like other houseplant vines to root and be ready for late May planting.
The Canadians have done refinement work on northern grown sweet potatoes and I will follow their lead in using black plastic. My experience last year with it was remarkable in the difference it made for plants. Instead of the "hills" that some say for sweet potatoes, the black plastic warms the ground and with the slightest depression the plastic acts as a funnel for rain and for watering in droughts to conserve water.
I hope some of those tips helps others as with the advent of all of these new methods and heirloom varieties rediscovered people can grow just about anything now with ease and enjoy the fruits of their labor. agtG