This is the time of year to start your sweet potatoes. It's easier than you think.
You need: sweet potatoes, water and jars.
Put the sweet potatoes in the jars. Fill the jars with water. Put them in the window. Let them root.
They'll send out roots like these. The warmer they are, the faster they'll root.
I've had mine in a window and it has not been warm. The roots have been slow to show, but they're all rooting. As soon as it warms up, they'll show a lot more action.
They'll shoot up leaves like these.
And in June [in zone 5], you can stick them in the ground. I cut them up so that each start has leaves and roots.
Sweet potatoes love warm. Wait until after the last spring frost to even think about planting them.