Our forecast says 12 for tomorrow night. My tactic for my mini garden outside (can't be moved anywhere more sheltered) is that I haven't watered it for weeks, cover with a sheet kind of backed up to a leaky window, with a giant tub of water under it, and a few dark rocks. So far so good, but 12 is way different than 22. If there was a way to plug electrical stuff in out there, I would run an aquarium heater in the tub of water.
If I was hoping an attached garage would help, I would try to put stuff up off of the floor, where the coldest air would be. That could make a difference. An unattached shed or garage, I wouldn't have much hope.
TY Ken for trying to save those plants out there!
