The nasturtium is not hardy and does not tolerate frost at all. The above-ground parts of the plant freeze with the first night frosts. If you want to overwinter your nasturtium, you should do something beforehand.
However, you should first make sure that your nasturtium is actually a perennial variety. There are now numerous new breeds with many color variants. Unfortunately, most of them are annuals.
Overwinter nasturtium properly
Cut back your nasturtiums from the flower bed in autumn and plant the bulb in a large pot. Put it in a bright and frost-free place, for example in the conservatory. How far you cut back the nasturtium depends, among other things, on the space available.
If you already have your nasturtiums in pots or boxes on the balcony or terrace, transplanting is not necessary. Just cut off wilted flowers and leaves and put the plants in their winter place.
You can limit the watering a little during the winter months. However, make sure that the soil does not become too dry.
Alternative to hibernation
If you don’t have space to overwinter your nasturtiums, but would like to plant the same varieties next year, then there is an alternative for that too. Take cuttings from your old plant or take seeds that you sow in spring.
The cuttings initially require less space and a smaller pot but are genetically identical to the original plant. In spring they can be planted out immediately after the ice saints and you don’t have to wait too long for the usual splendor of flowers.
If you have decided to collect the seeds, you should dry them carefully so that they do not become moldy. In March, you can start sowing on the windowsill or in the heated greenhouse.
Before wintering, check your seed packet to see if you bought an annual or perennial variety.