Most cacti and succulents easily withstand temperatures well below zero, so they can be left outdoors all year round. Exposure to periods of low temperature favours flowering in spring. To be able to survive the cold, however, these plants must enter a dormant stage and should not be watered, especially when the thermometer is showing very low temperatures. Starting in the autumn months you should begin to suspend watering, so that the soil dries out completely. Put your plants somewhere bright and sunny, but sheltered from the elements. Where possible place the plants under a roof, or leave them in the garden but protected with well-dried straw and plastic film, so that precipitation cannot reach the root system. The best place to keep cactus in winter is definitely a little cold greenhouse, completely unheated, but away from water. The greenhouse can be small, but try to keep it healthy for your plants before putting them in by cleaning it, also carrying out total pest control by disinfecting it with a fungicide and insecticide spray. Put your plants in a sunny location, and close to the house if possible, to increase the temperature inside the greenhouse, further protecting the plants from frost. Inside the cold greenhouse avoid crowding the plants, placing them so that they can enjoy good ventilation, and remember to open it to the air during warmer and sunnier days, to prevent the formation of condensation on the plants.