Even an exotic plant like the calla can survive our winter unscathed. We show when, where and how to overwinter callas successfully and how to properly care for them during the cold period.
The Calla (Zantedeschia aethiopica) is often also called Zantedeschia. What is meant is an exotic plant that impresses with its large, impressive flowers. It can be used as a houseplant in a pot for a jungle feeling in the home or office, or decorate the garden with its blooms in summer. But with one exception, these plants cannot survive the winter outdoors in our country. In this article, we explain how your Calla can still be preserved for many years.
Are callas hardy?
The calla lily does not come from Ethiopia, as the botanical name Zantedeschia aethiopica would suggest, but from South Africa. There the plant is spoiled with warm temperatures all year round, which actually never fall below 20 °C. Accordingly, callas are not hardy and cannot spend the winter outdoors with us. But as we all know, exceptions confirm the rule. There is actually a Calla variety that was specially bred for frost tolerance. 'Crowsborough' flowers in summer and is said to withstand temperatures down to -20°C. In concrete terms, this means that in winter the above-ground plant parts of this hardy Zantedeschia variety freeze or are cut back by you. The tubers remain in the ground all winter and can sprout again in spring. With callas becoming more and more popular in the garden, it is certainly only a matter of time before new frost-tolerant calla cultivars are bred.
Summary: Are Callas Hardy?
- Normal calla cultivars are not hardy
- The only exception is the variety 'Crowsborough'
- As a tuber, it can survive temperatures as low as -20 °C
Tip: Make sure your calla lily is really Zantedeschia aethiopica . It easily gets confused with the swamp calla (Calla palustris), toocalled Drachenwurz, which, in contrast to Zantedeschia, is native to the northern hemisphere and is very hardy.
Overwintering Calla correctly: Our care tips
Zantedeschia does not have four, but only two seasons in its native South Africa: the dry and the rainy season. Therefore, the Calla also needs strict growth phases for a magnificent growth. This means that during the growing season in summer it needs the highest possible temperatures and enough water, while in winter cool temperatures and drought are needed. In the next sections you will find out how to create the ideal conditions in winter for both the indoor calla and the calla in the garden.
When will the calla get too cold?
Callas or Zantedeschias are unfortunately frostbite and are quickly damaged if the temperatures are too low. Room callas in pots get too cold at temperatures below 15 °C and they should be brought into a warm room quickly. Zantedeschias, which are planted out in summer or spend them in pots in the garden, need appropriate measures from temperatures below 10 °C in order to survive the winter safely. As already mentioned, the only exception so far is the hardy Calla variety 'Crowsborough', which can withstand temperatures down to -20 °C.
Overview: When does Zantedeschia get too cold?
- Room Calla: From temperatures below 15 °C
- Garden calla: From temperatures below 10 °C
- 'Crowsborough': As a tuber, it can withstand frost down to -20 °C
Wintering Calla: How and where?
The hibernation of indoor callas and garden callas differs significantly. While indoor callas can overwinter as a whole plant, callas are dug up from the garden in the fall and only the bulbs are stored over the winter. First, let's take a look at how best to overwinter your room calla: Even in winter, the Zantedeschia needs a location that is as bright as possible, for example on the windowsill. However, you should definitely avoid direct sunlight. The temperature becomes critical, because it should remain constant throughout the winter and, if possible, not fluctuate. At a constant 10 °C, the calla in the pot survives the winter unscathed.
Summary: Overwintering calla in a pot:
- As bright as possible, but no direct sunlight
- Ideal temperature: 10 °C
- No temperature fluctuations
With the garden calla lily, a few more steps are necessary to get the plant through the winter well. Start preparing as early as August by stopping the fertilization completely and gradually reducing the watering. At the beginning of October it is then time to dig up the storage organs of the plant, the tubers. Only they are overwintered. From the excavated callas, cut back all above-ground plant parts to two inches. The soil is also carefully tapped or brushed off the tubers. Now dry the tubers on a grid for two to three days. Then the Zantedeschias are ready to move into their winter quarters. A dark, dry place, such as a basement, is ideal for this. During the winter of the callas, the temperatures should never rise above 15 °C, otherwise the plants will start to sprout. However, the temperatures should not fall below 0 °C, otherwise the tubers will freeze to death. Place the tubers in a box filled with dry sand or straw. In this way, the calla bulbs can rest over the winter and be planted out again in the spring.
Wintering Garden Calla: Summary:
- Water less from the end of August, stop fertilizing
- Dig the tubers out of the ground at the beginning of October
- Cut back all aboveground plant parts to 5 cm
- Remove Earth
- Let tubers dry for 2 - 3 days
- Winter in a box with dry sand or straw
- Store in a frost-free, dark and dry place
- Temperatures should never exceed 15°C
Caring for Calla in Winter
As already mentioned, winter is the dry season for calla lilies. That is why it is only poured very sparingly. Allow the substrate to dry out almost completely before watering again - in very small quantities. There is no fertilizer at all in winter. Unfortunately, Zantedeschias are often plagued by pests during the cold season. Therefore, check the plant regularly for pest infestation. Typical pests of the calla lily are aphids (Sternorrhyncha) and spider mites (Tetranychidae). Withered leaf edges and discolored leaves, on the other hand, indicate root rot caused by too frequent watering. If you regularly remove dead plant parts from your houseplant,your calla does not need pruning. In spring you can slowly prepare the calla for the rainy season by first increasing the temperature to 12 to 15 °C. Now the plant is slowly starting to grow again and therefore needs more water again. But don't overdo it too much in the beginning, still water moderately. Garden callas that are overwintered as tubers do not require maintenance over the winter.
Caring for Calla in Winter - Overview:
- Water callas very sparingly
- No fertilization
- Check regularly for pest infestation
- Remove dead plant parts regularly
- In spring, slowly increase the temperature to 12 - 15 °C
- Constantly increase the amount of water, adapted to the growth
- Callas that are overwintered as tubers require no care
Tip: Always wear gloves for all care measures, because all parts of the calla plant are poisonous.
If you have let your calla hibernate as a tuber, you have two options for overwintering the plant in the spring. Either you plant the tubers in a pot first and let them grow indoors, or you save yourself this step and plant the tubers directly outdoors when no more frost is to be expected. Planting the bulbs in pots first will give the plants an advantage and they will start flowering earlier in the year. To do this, prepare a pot of potting soil that you enrich with a slow-release organic fertilizer. Our Plantura organic flower fertilizer is particularly suitable for this, as it contains all the important nutrients for your calla. Now the tuber is placed ten centimeters deep in the pot, covered with substrate and watered. The calla can then grow well in a bright place at room temperature. Water them regularly and increase the amounts of water in proportion to growth. The plant can finally be transplanted outdoors in mid-May.
Alternatively, you can also plant the overwintered tubers directly outdoors at the end of May - whether in the garden bed or in a pot is up to you.
How should you overwinter garden calla?
- Get tubers out of winter quarters at the beginning of March
- Fill the pot with substrate and a long-acting organic fertilizer
- Plant the tuber 10 cm deep
- Water well
- Put in a bright place at room temperature
- Constantly increase watering quantity in proportion to growth
- Plant out in mid-May
- Alternatively, no preparation in spring, but plant tubers directly in the garden bed or pot outdoors in mid/end of May
Not all plants need to be overwintered with as much effort as the calla. Many perennials, for example, are hardy and can easily survive the cold season in the garden. Here is an overview of our 10 most popular hardy perennials.