Stop watering your cacti while they overwinter.
Most cacti come from hot climate zones where there is little rainfall and the plants bathe in sunlight. Cacti produce beautiful flowers, some of which are breathtakingly fragrant.
In temperate countries, in the warm months, they can thrive on balconies, south-facing windowsills or porches. However, as soon as the temperature drops to 0 °C, make sure to bring them indoors for the winter.
A particularly important factor for a healthy overwintering is to suspend watering and nutrient supply. Cacti can remain in their dry planting medium throughout the winter. Remember that in nature these plants often do not have access to water for a whole year!
Place your potted cacti in a dimly lit spot where the temperature is between 4 and 12 °C. An unheated stairwell or basement may be the most suitable. In such conditions, the plants go into a dormant state, from which they can slowly be brought back again in the spring. Around this time, make sure to gradually reacclimate your cacti to light and rising temperatures again.