To overwinter geraniums in paper bags, dig the plants up before the first frost of the season, and remove the dirt around the plant's roots. Cut the plants back by one-half, and place the plants in large paper bags. Store the bagged plants in a location with temperatures that range from 45 to 50 F, allowing the paper bags to remain open during storage. If the stems shrivel, soak the roots in water.
When digging geraniums up to store them, use caution to ensure the root system remains intact, and remove the dirt from the roots carefully to avoid damaging the plant. Examine the plants monthly during the winter. If the stems are shriveled, soak the roots in tepid water for one to two hours. Allow the plants to dry before placing them in the paper bags again.
The foliage typically falls off geraniums during winter storage, but the stems remain firm if the plant is healthy. Discard plants with blackened or very shriveled stems, as these plants typically die before spring arrives.
To revive geraniums in spring, soak the entire plant in water overnight, pot as usual, and place the geraniums in a sunny location indoors. After the last expected frost of the season, plant the geraniums in the garden.