Geraniums are often grown as annuals, but they are actually tender perennial plants. They cannot survive any frost, so they must be brought inside to overwinter in a protected place. There are several ways to overwinter geraniums, depending on how much time you want to invest in the process.
Bring potted geraniums indoors before the first fall frost. If plants are growing in garden beds, dig them up and transplant them into a 8-inch diameter pots before the first fall frost damages the plants. Geraniums can continue to grow indoors if you have an area that supplies them with at least four hours of direct sunlight a day throughout the winter months. They need enough water to keep the soil moist and fertilize them once a month.
Instead of storing and overwintering the entire geranium plant, take cuttings from existing plants before they die off in winter. Take 4 inch long cuttings from shoot tips, choosing shoots that have at least two leaves on them. Dip the cut ends into a rooting hormone, available from florists, and then plant each cutting into a pot filled with a sandy soil. Keep the soil moist and provide plenty of sunlight throughout the winter months. The cuttings form their own root systems and grow into new geranium plants over the winter. They are ready to replant in the garden the following spring.
Dormant geraniums require little care during the winter months, so they need the least amount of maintenance. Once dug, shake all the soil from the geranium’s roots. Set the plants in open paper bags, which allows some airflow around the plant. Plants quickly go dormant if stored in a dark, 45-to-50-degree F room. Soak the roots in water for two hours once a month so the plants don’t completely shrivel and die during storage. In early spring, pot the dormant geraniums and begin supplying water and sunlight. Plants that survived storage will quickly begin putting on new growth.