At the end of summer it always seems like such a shame to toss some of the geraniums that have done exceptionally well. I have successfully found a formula that works to over-winter geraniums without having them take over the living room for the winter months.
Leave your plants out until the weather starts to really turn, as in frost warnings. Geraniums actually like cooler temperatures, but will not take a frost. When it is time to take them in, place them in your basement. Near a window is not necessary. If you wish you can cut them back a little, but I usually just put them down there and forget about them. They will turn brown and drop their leaves. You don’t have to water or anything. When the calendar turns to late February, I take them up to a room where there is a sunny window. They will have grown long thin pale green shoots by now, this is your indicator that the plant is still growing. Clean off the dead leaves and cut back the plant on the stems just above where the thin green shoots are. Water well and fertilize. The plants will start to bud out. After a few weeks trim the plants back again. This will result in a lush thick plant, not the thin branchy plants that are typical of over-wintered geraniums. Once the weather is warm enough, move outside into the full sun, but not in a cool breezy spot. Be sure not to leave out if too cool or the threat of evening frost. The plant is still coming out of it’s dormancy and will not tolerate significant temperature changes. Follow these guidelines and you will have just as lush of a plant as the previous summer.