Caladiums require a warm, moist soil. A minimum of soil temperature of 78-80 F is preferred. If planted too early in spring, cool soil temperatures will cause tubers to rot before they sprout. They can be started indoors in moist peat moss or potting soil in containers such as a shallow flat or flower pot. Barely cover tubers with soil and place the container in a warm germination room with bright light. Tubers should be started indoors approximately four weeks before planting outdoors.