Frost-sensitive Beauty: Overwintering Calla

Except for a few exceptions, Callas are not winter-hardy. These South African beauties cannot tolerate freezing temperatures. Therefore, you should overwinter Callas.

Callas go through various phases to thrive. You must ensure to follow these phases. During the growing season, they need plenty of warmth and water, while in low temperatures, especially in winter, they require almost complete dryness. If you keep Callas in the garden during the summer, bring them indoors to overwinter.

Callas, also known by their botanical name Zantedeschia, cannot tolerate frost. Even if they are labeled as hardy, they can only survive very mild winters in the ground. The bulbs can thrive outdoors only when temperatures are consistently above 10°C. Therefore, plant Callas in the spring, once there is no more risk of frost, including night frosts. To shorten the time until blooming, you can start the bulbs in pots as early as March. This way, you'll enjoy the exotic flowers in your garden sooner.

If your Calla spent the summer in the flower bed, you should dig up the bulbs by early October, ensuring that no frost has occurred by then. Carefully dig up the bulbs using a digging fork to avoid damaging them. Remove the leaves and clean the bulbs. Discard any diseased bulbs and leave the healthy ones to dry. If the bulbs are not dried properly, mold and rot can occur. The winter storage area should be dark, dry, and kept at a temperature between 10 to 15°C. A cellar is an ideal choice, but garden sheds and garages also work well. Do not stack the bulbs, and make sure they are not placed too closely together to avoid crushing or soft spots. Check the bulbs regularly.

Not all Callas behave the same way. Some are evergreen, while others shed their leaves during the resting phase. Evergreen Callas are overwintered differently. They should be planted in a pot and placed in a bright spot. The winter location for these Callas should also be around 10°C. During their resting phase, the room Calla does not need water or fertilizer. Allow the soil to dry completely. Only from January onward should you start acclimating the Calla to warmer temperatures. Repot the plant and gradually begin watering again. At this point, you can also apply some flower fertilizer every two weeks. Once new shoots appear, keep the soil moist for the Calla.