Almost every plant we grow will be okay in a container for at least one season. The difficulty comes in overwintering a perennial in a container in colder zones. Since the roots are now "above ground" in the container, the moderating effect of the soil's warmth is lost. Either transplant the perennials into your fall border, or sink the entire container in the ground. In mid zones, you might get away with protecting the container with hay bales or mulch, or by placing the container along the sheltered foundation of your house. If you freeze the roots on a shrub or perennial, you’ll probably lose the plant.