Carolyn, I'm zone 6/7. I think late march is your best bet. If you had a crystal ball and knew that it wouldn't be too hot in June, you could wait until late April. Never tried in Jan or Feb. I've planted every other month, and the biggest failures were when I planted in late May and June and then had extremely hot or windy weather right after.
If you have long mild springs, they'll do fine with March, April, into May. Don't know about Feb--depends on your soil. Our soil just now froze. The weather patterns this winter have been so strange, who knows what's going to survive or thrive. (Our spring lasts about 3 days. We go from freezing to hot winds very quickly!)