Fortunately for growers of this garden annual, geraniums can be saved if brought indoors before the first frost. With minimal overwintering care, geraniums can then be replanted outdoors in late spring and enjoyed the following summer.
Prepare geraniums for winter by pruning the plants and repotting them indoors, placing them near a window that receives abundant sunlight. Alternately, take cuttings from established plants; place them in rooting hormone and replant in vermiculite or coarse sand. New roots develop six to eight weeks later.
In early spring, repot overwintered geraniums indoors in fresh soil and keep in a location receiving 10 to 12 hours of sunlight daily. Ideal indoor temperatures for geraniums range from 65 to 70 degrees Fahrenheit during the day and 55 to 60 degrees at night. Water soil as needed and fertilize. New buds and shoots will begin to form within a few weeks.
Replant geraniums outside in late May, or safely past your last-frost date, discarding any shriveled or brown stems because they most likely will not grow.