You will kill the caladium bulbs if you do not dig them up. These caladium plants and their bulbs cannot tolerate cold temperatures, frost, or freezes. Growing them as annuals requires digging them up from your garden at the end of the blooming season, which typically means the end of summer when the leaves begin yellowing as fall comes. You collect the bulbs, then winter them inside in a dark, cold room. If you have a basement, that is perfect. They will go dormant in the dark. Leave the foliage attached to the caladium bulbs. Once the roots dry, trim off the leaf stems. Brush off the loose dirt. Store them in a dry room at 50°F. When you re-plant them in the spring, you can count on them to grow bushy foliage and to bloom on their regular schedule.