Experts and BHG readers answer.
It's possible your container boxwood could come through a mild winter outdoors unscathed, but I wouldn't risk it. Container plants are more exposed to the weather than those in the ground. An unheated garage will offer great protection for your boxwood during the winter months. The plant will be dormant (resting and not actively growing) so it won't use much water, but you'll still have to water once in a while.