The indoor calla comes from southern Africa. It is not hardy and, with a few exceptions, cannot tolerate sub-zero temperatures. How to properly overwinter calla lilies in a pot or as a flower bulb.
Are calla plants hardy?
Calla plants are generally not hardy and cannot tolerate sub-zero temperatures. You should dig up calla bulbs in autumn and store them in a cool place, while calla in pots overwinter in a bright and cool place. An exception is the hardy calla variety “Crowsborough”, which can overwinter outdoors with winter protection.
Overwintering calla as a flower bulb
- Dig up in early October
- Cut off yellow leaves
- Remove soil
- Let the onion dry out
- Store in a cool place
- Plant out in spring
Get the garden calla tubers out of the ground at the beginning of October at the latest. Rub off the soil and cut off the yellow foliage.
Let the onions dry thoroughly and then place them in a place that is about ten degrees cool. The basement is well suited.
Always plant calla bulbs in spring
The onions are put back in the garden in spring. For this to happen, the earth must be at least ten degrees warm. Frosts are no longer allowed to occur.
The planting instructions for new tubers often state that you can plant them in the fall. You shouldn't rely on that. Even tubers that are designated as hardy are almost never winter-proof. They only survive very mild winters in the cold soil in the flowerbed.
Bringing calla lilies in the pot over the winter
There are different varieties of indoor calla lilies. Some of them are evergreen, while others completely withdraw their foliage when they are dormant.
You can overwinter the evergreen calla in a pot. Place it bright and cool at around ten degrees. Make sure that the plant is not in the draft.
During the winter, the plant is not watered or fertilized. The earth must dry out completely.
Calla slowly getting used to warmer temperatures
Depending on the variety, the calla will get used to the warm flower window again from January. Beforehand, repot the plant in new soil.
Start watering slowly and give the calla some flower fertilizer every two weeks (€14.00 on Amazon).
As soon as the first new shoots appear, keep the soil moist at all times.
Winter hardy variety “Crowsborough” outdoors
The “Crowsborough” is a white calla variety that is relatively robust. According to the breeder, it can tolerate temperatures down to minus 20 degrees. So you can leave the tubers in the ground over winter.
However, you should still ensure winter protection by only planting the tubers in somewhat sheltered locations.
In autumn, cut off the above-ground parts. Cover the planting site with a blanket of dry leaves. As soon as the temperatures outside rise to over ten degrees again and night frosts are no longer expected, remove the winter cover. The ground can then warm up more quickly.
Tips & Tricks
Do not confuse room calla with the swamp calla (Calla palustris), which is often grown in ponds. In contrast to houseplants, swamp calla is hardy and does not need to be overwintered indoors.
