I think it's the wet they don't like more than the cold. At least that's what I'm hoping! I get nervous when they give Zone 5 as it's coldest allowable -- right next to the house in sheltered areas we can create that as a microclimate, which is what I'm planning for with all my seedlings. And of course, no wet feet!
Did the one you brought inside make it, Greg? Thought they had to have a real winter? If they did make it, I'm thinking maybe I should bring my seedlings indoors instead of leaving them outside? MR