Last year an attempt was made to grow sweet potatoes in my garden. I bought an organic sweet potato and started the slips in water. Once they were big enough I planted them and they were growing great. Living in manitoba I was worried about the cool nights in spring. I placed windows on top of the raised beds. The issue was I, on occasion forgot to remove the windows and baked my plants. They persevered but due to the early season abuse, they only produced Pinkney sized sweet potatoes. In future years I will not put them in cold frames to prevent this.