I am not sure what you are asking Darlene, but if it is how cold can the garage get before you induce heat, I would say 40 degrees. I put mine in my garage during cold snaps (we very rarely have more that a couple of days in a row of freezing or below freezing temps) and the temps in the garage are in the 40's to 50's. I get no die back, they usually lose most of their leaves from going in and out. I usually leave them outside unless it gets below 38 - 40 degrees. I have some in the ground and some in rooting pots that stay out all year and do fine with just minimal die back.
John