That's when I usually plant mine, but I was several weeks late this year. I've started my slips from the previous years harvest for many (20?) years now. I can't remember the variety now, it's been so long ago when I first got them. I'll have to look that up.I think I planted first week in june. Sweet potatoes dont like cool weather. I plan on taking the three largest to the local fall festival next week. Dug these by hand, the plow is hard to use without breaking them.