In a 6b zone I have to grow some annual and perennial flowers by the end of May, meaning that they must be flowering by then. I have tried to make a rehearsal of some sorts, but we had freezing temperatures until the first days of May 2016, so last year I have transplanted them a little late (they were grown indoors from seed). The result was that they came in flower in mid-July.
Some of the species are Tropaeolum majus (or minus), Centaurea cyanus, Lavatera trimestris and Alcea rosea and I was wondering how to protect them in case I want to plant them earlier, let's say in March.
My plan is to make raised beds and any advice on how to protect them is most welcome. I also have to mention that the land is on a north-faced hill, but the slope is barely noticeable in the area I will make the raised beds.