To overwinter geraniums, dig the plants up and place them in open paper bags. Take the plants indoors, and place them in a cool, sunny location.
Geraniums can survive through the winter months without soil if the plants are stored properly. Inspect the geraniums for signs of disease, and dig up the healthiest plants in the garden. Remove any loose soil on the roots, and place each plant in a paper bag. Allow the bag to remain open to ensure the roots are properly ventilated. If storing the plants in a paper bag is not possible, hang the geraniums upside-down from rafters in a cool, dry area.
Geraniums should be stored in a location with temperatures that range from 45 to 50 degrees, and the roots should be watered at least twice during the winter months. To water the geraniums, soak the roots in water for 1 to 2 hours.
To prepare geraniums for replanting in the garden, place the plant in a container with the appropriate growing medium, and water each plant thoroughly. Cut any dead tips off the branches, and place the containers in a warm location with direct sunlight, such as a sunny window. Allow the plant to remain indoors for several weeks to encourage new growth, and transplant the geraniums to the garden after the last frost of the season.