Geraniums tend to be almost as common as weeds in warmer states such as California, but in Iowa they are cherished for their brilliant blooms. However, they are not winter hardy and most people buy new plants each spring.
However, you CAN winter over your geraniums. There are three ways to do this. You can bring the pots indoors and place them near a bright window or a patio door where they will continue to grow. Many times, though, the short daylight hours cause them to grow long and leggy. In that case, trim them back about mid or late February and they'll put out new growth.
But this takes up a lot of space if you have a lot of plants. The second option is to pull up the plants by the bare roots and store them in a paper grocery bag in a cool, dry, dark basement. The plants will shrivel up to nothing and appear dead. In late February or March repot them, give them plenty of light, and watch them grow.
In the first photo newly repotted plants show just a smidgeon of new growth. (Click on the photo for a closeup. Actually, I should have trimmed back much of the dead branches on this plant.)
The third option is to place pot and plant in a dark, dry basement. The plants will appear to die. I cheat a bit and perhaps once a month give them just a bit of water to entice them to live. In the second photo, you can see new growth on potted plants that I wintered pot and all in the basement. The plants had dried down to almost nothing and after bringing them upstairs I carefully trimmed them back to live stems. Today we are getting a quiet, misty rain and I've placed them outdoors, mindful to check nighttime temps, just in case it freezes.
By the way, sandwich trays or dinner plates from the thrift store are perfect under the pots to protect your floor or deck from water and dirt.