I live in a condo, and I'd like to prevent the potted roses growing nicely this Chicago summer from freezing to death in a Chicago winter. I'm neither allowed to couple the pots into my condo building (by using soil piled up around the base of the building) nor is my garage suitable because it's too warm.
My main question is: what's a good minimum temperature for potted roses (soil and all)? I want them to stay dormant during the winter without prematurely waking up. Since I'm an electrical engineer, I can rig pipe heating tape around the pots and insulate them for winter to provide a minimum temperature floor. I just need to know the right temperature. Around 33 degrees Farenheit or so would be convenient since pipe heaters already have thermostats that provide that minimum temperature.
Thanks in advance.