Answer: You can treat them as houseplants for the winter if you have space. They require lots of sun and watering about once per week. Feel free to cut them back, since they'll send out new, tender growth and blooms. If you don't have room for them, put them in dormant storage.
Gradually reduce watering, and when the foliage dies back, store them in a dim, cool (40-45F) basement or garage. Check them occasionally during the winter to make sure they don't dry out completely. When danger of hard frost has passed, repot, water, and place them outside. After a year or two, your geraniums will become woody and produce fewer blooms - at that point, you can start new plants from cuttings.
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