Use the short, dark days to flood the plant with water so that it wilts. Cut off the foliage and overwinter the tubers in a dark and dry spot in their potting soil at a temperature of around 8 degrees, i.e. so that they stay out of the frost. In this state without the foliage, the plant can happily remain in the dark. Two or three times during the overwintering period, give the plant a small to moderate amount of water so that it does not dry out. However, do not allow the plant to become too moist.
At the end of February/start of March, repot the plant in mineral potting soil (e.g. frux potting soil) and the tuber will gradually sprout again in a bright spot as you slowly increase the quantity of water and temperatures begin to rise. From the middle of May, you can then take the plant outdoors but don't forget to allow it to get used to sunlight and outdoor temperatures again. To do this, it is best to place the plant in a warm, sheltered and partially shaded spot for fourteen days.
The colourful canna called "Tropicanna" can be overwintered at 15–18 degrees Celsius in a bright to half-shady spot in a warm conservatory; if you do this there is no need to remove the foliage. During the overwintering period, you can give the plant a small to moderate amount of water and a third of the liquid fertiliser quantity that you would normally use in summer.