I know I'm in FL zone 9b, but have a lot of pentas in ground and in containers. They survive temps as low as 30 with little or no damage so pretty cold hardy. If they do freeze down some, we have had several hours in the upper 20's, they come back, with a bit of pruning. I've never tried rooting them before, but worth a try. If it is in a container, moving to a protected area good, but if in the ground, toss a cover over it when freezing temps.