if you don't want to go through all the trouble of digging and storing in pots, you can cover them with a thick layer of mulch followed by a thick layer of fern fronds. we have several varieties of salvia, including our favorite, Black and Blue, here in Washington, and they come back every year. of course we don't have super cold winters like you do in Mn., but we do have 10 months of cold, soggy rain. somehow they survive without getting root rot. its worth a shot!
