Mine tolerate outside winter fine but my winters are much milder than yours. Van you create some sort of semi-protected environment for them out there that will insulate them from freezing temps and the worst of the snow. They make foam domes used for winter protection of roses that work well but they also block the light so you'd have to keep taking them off and putting them on. I'd be tempted to try cutting off part of the top of one and replacing it with glass or plastic. Think outside the box about some sort of mini-greenhouse type set up.

Dave

Dave, that's exactly what I was thinking but wasn't sure just how effective it would be for their first winter. Thanks very much for your input.

Cut top out of 2 or 3 litter bottle...The bottom side a perfect come... :)