I monitor what people are looking for when they access my blog. I like to see what is driving other gardeners and wanna-be gardeners. I mentioned I will be growing sweet potatoes this year and that got a hit. Talking to my sister-in-law, with whom I will be gardening this year, I realized that while she and her boys love sweet potatoes, she didn't realize that they could be grown here.
So as I have some experience growing sweet potatoes here in central Wisconsin, I will relate what I know.
It starts out with, they like it hot!
Last year, A friend and I grew them from tubers. I think she had okay yields. As they were grow at her place I did not participate in the digging, I only know what she related to me. The vines were incredible. They looked very healthy. I do not know which variety, nor do I think does she. They were planted after the first week in June.
The key is sweet potatoes like fully warmed soil. That means night temps are above 50 degrees, and I would assume the soil temps are getting close to 70 degrees.
A commercial grower of sod and annuals got a USDA grant to grow them from slips the year previous and had a conversation with me about it in early May. They were a bit concerned as no one grows them here and growing them from slips seemed a bit chancy.
This same grower thinks nothing of pumping out flats of ornamental sweet potato vines from cuttings. I pointed that out and suddenly a light came on. The ground needs to be warm. They need adequate watering during the rotting in, but not so much during any cool snaps that they are set up for rot.
The other thing I would mention is from my reading, I believe 'Georgia Jet' is probably a better yield and more acclimated to northern climates. So I would try that variety first.
If you over fertilize them with nitrogen they are going to grow vine. The tuber production is going to be better if you have adequate phosphate available for your plants. That's the middle number in the "x-x-x" on fertilizer bags.
Today I intend to prune grapes and take pictures while I do, so hopefully I'll get my blog on grape pruning up tomorrow.
Have a sunny spring day!