Geography

• The crinkly, swollen storage organs called tubers are not killed by cold when left in the soil over winter in mild climate regions. In U.S. Department of Agriculture plant hardiness zones 9 and warmer, gardeners leave tubers in the ground, perhaps with a shallow insulating mulch atop the soil. The tubers sprout new leaves in late spring when it's amply warm. Elsewhere, in USDA zones 8 and colder, the winter cold is severe enough to penetrate deeply into the soil and kill the tubers.
  
  

When to Dig up Caladiums

• Caladiums need a soil temperature between 70 and 85 degrees Fahrenheit to grow lush with lots of leaves. As summer wanes in your climate, little by little the leaves wither from the caladium plant. Once the first fall frost kills back all leaves, it's time to lift the tubers and prepare them for storage. The tubers remain safe for a couple weeks after the first frost since they're insulated by soil. Erv Evans of North Carolina State University recommends digging up the tubers before the soil temperature about 4 inches deep drops below 55 degrees Fahrenheit.
  
  

Lifting the Tubers

• Carefully slice into the soil with a shovel or hand trowel to expose the caladium tuber. Gently break off any clinging soil on it. Any tuber you accidentally cut or break needs to be discarded. And, any tuber that is mushy or smells of sulfur is already rotting and is not worthy of overwintering. Allow the tubers to air dry in a dry location out of direct sunlight, where the temperature is between 60 and 70. After seven days of drying, complete any further brushing off of soil, or removing shriveled leaves and stems.
  
  

Winter Storage

• Gary Wilfret, a renowned caladium breeder and expert from Florida, suggests dipping tubers in a fungicide before putting them in storage for winter. Although not mandatory, the fungicide discourages rot. Ground cinnamon also acts as a natural antifungal agent. Place the dry caladium tubers in an open mesh onion or orange bag with dry sphagnum or coarse sawdust. A lightweight paper bag also works as long as the bag isn't sealed shut so air circulation remains. Keep the stored tubers in a cool, dry location where the temperature remains above 60, such as in an unheated room or insulated but unheated garage.