The GARDENA gardening expert
Dear Ms W., the white calla houseplant is indeed somewhat tricky. But if you proceed as follows, you will succeed in having them grow and prosper. The secret to the correct care of this plant is to maintain its care in this country as though it was living through the natural lifecycles it would experience in its native land, Eastern Africa. In its African home, it grows on marshy meadows which dry out in summer. This means that the Zantedeschia maintains a summer rest phase, during which it withdraws its leaves. That is why we often read the advice to remove it from the soil at this point and replant it later on. In principle, this advice is correct, but the process can be avoided if you feed the plant sufficiently during the main growth period and encourage it not to withdraw by giving it a little water in the summer. The white calla lily (Zantedeschia aethiopica) does not necessarily require this rest phase in this country, as long as it is given sufficient water.
I don’t know the details on how you have cared for your calla in the past. It may well be that your plants wish to withdraw their leaves now in order to enter the rest period. However, this doesn’t matter, even if you do lose the current flowers. The plant will make up for this in spring, when you “reset” it and reorganise the lifecycle of your plant.
If applicable, allow your calla to withdraw now and then leave to rest dry approximately three to four weeks at 10 to 12 degrees Celsius. Then clean the rhizomes and plant them into quality cultivation soil. Initiate their growth in a well-lit location with slow watering of the shoots, and then adapt the watering quantities to the plant as it grows larger accordingly (the water requirements will increase). In summer, you can place your callas outside once more, but preferably protected in a warm and well-lit location. First of all, allow them to get used to their new location – otherwise the sun may burn their leaves.
If you now supply the callas with sufficient water in summer, but only with just as much water as they need, they will not generally withdraw their leaves, and will flower much better later on. In this case, they will retain their leaves, and you can relocate them back in the house. From autumn to December, keep the plants cool at 10–12 degrees, and then at 13–15 degrees Celsius, and always in locations which are as well-lit as possible. During this time, stop fertilisation, and do not fertilise the plants with flowering plant fertiliser until the first buds begin to show, then continuing until they stop flowering.
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