Firstly, Liz, you did it right, and the photo is a cracker! I'm glad I'm not the only one still using Photobucket
I think you may have winter temperatures below what these plants can cope with. Why not plant them in a big pot, keep them indoors over winter - they do not need light because they are dormant, so a garage or out-building will do. Take them out in spring, dig a hole and plonk the pot in. It will look as though they are growing there. But you can lift them and take them back inside when the temperature drops.