Caladiums are tropical plants known for their colorful foliage, but they cannot tolerate cold temperatures, making winter dormancy necessary in cooler climates. This resting phase allows the underground tuber to conserve energy and regenerate for the following year’s growth. Overwintering potted Caladiums involves carefully managing this natural dormancy cycle to protect the tuber from freezing or rotting. This ensures the plant’s successful return in the spring.
Signaling the Dormancy Period
The first step in overwintering is recognizing and initiating the dormancy phase, which is primarily triggered by environmental changes. As autumn approaches, cooler temperatures, especially those consistently dipping below 60°F (15°C), and the natural shortening of daylight hours signal the end of the active growing season. The Caladium begins transferring stored energy and nutrients from the leaves back down into the tuber to prepare for rest.
Immediately cease all fertilizer applications, as the plant is no longer actively growing. Gradually reduce water input once the foliage begins to yellow, droop, or dry out. Allowing the foliage to naturally yellow and die back is important because it ensures the maximum amount of energy is pulled back into the tuber. Once the leaves are completely dry, which usually takes several weeks, cut the remaining stems back to about one inch above the soil line.
Preparing and Curing the Tubers
After the foliage has died back and the soil has dried, decide whether to store the tuber in the pot or lift it. If lifting, gently remove the tuber from the soil, avoiding piercing the soft tissue. Brush off excess soil, but avoid washing the tuber with water, as introducing moisture promotes rot during storage.
Inspect the tuber surface for any signs of damage, soft spots, mold, or pests, such as root mealybugs. Any small, rotted sections can be cleanly cut away using a sterilized knife to prevent decay from spreading. The next step is “curing,” which involves allowing the tuber to dry and form a protective, calloused layer over its skin.
Curing should take place in a warm, well-ventilated area, ideally between 70°F and 90°F, for one to two weeks. Spread the tubers in a single layer on newspaper or a cardboard tray to ensure they dry evenly and quickly. This drying process hardens the outer layer, significantly reducing the risk of fungal or bacterial infections during dormancy. Some gardeners dust the cured tubers with a fungicide powder before storage for added protection against rot.
Ideal Winter Storage Conditions
Storage conditions must be stable, cool, dry, and dark. The temperature is important; it must be cool enough to keep the tuber dormant but warm enough to prevent damage. A range between 50°F and 65°F (10°C to 18°C) is recommended for successful overwintering. Temperatures that drop too low can cause erratic growth or stunting when the tuber is replanted.
The storage medium must be dry and breathable to prevent moisture accumulation, the primary cause of tuber rot. Suitable materials absorb residual moisture and include:
- Dry peat moss
- Vermiculite
- Sawdust
- Shredded newspaper
Layer the tubers within this medium in a container that allows for air circulation, such as a paper bag, mesh bag, or open cardboard box. Avoid airtight plastic containers, as they trap humidity and quickly lead to spoilage.
Check the stored tubers periodically, perhaps monthly, to ensure they remain firm and dry. If any tuber shows signs of shriveling, indicating excessive moisture loss, lightly mist the surrounding storage medium to increase humidity slightly. Conversely, immediately remove any soft or moldy tubers to prevent the spread of decay. The dormant period requires at least 10 weeks for the tuber to fully regenerate its energy reserves.
Reintroducing Caladiums in Spring
The final stage involves waking the dormant tubers and preparing them for the next growing season. Timing is determined by the need for consistent warmth. Take the tubers out of storage and prepare them for planting about six to eight weeks before the last expected frost date, allowing for a head start indoors.
Caladiums require consistently warm soil and air temperatures before they sprout. They thrive when the soil temperature reaches at least 65°F (18°C) and the air temperature is reliably above 60°F (15°C). Use a fresh, well-draining potting mix when repotting, as this prevents fungal issues and provides new nutrients. Plant tubers shallowly, about one to two inches deep, with the “eyes” or growth points facing upward.
After planting, water the soil thoroughly and place the pots in a warm location with bright, indirect light. Heat is a greater stimulus for sprouting than light, so bottom heat, like a heat mat, can accelerate the process. Once the first new leaves emerge, begin a regular watering and fertilization schedule, slowly acclimating the young plants to outdoor conditions once all danger of cool temperatures has passed.