There are several ways to save your geranium over the winter for next year:
1. Take cuttings and root them. Take 4 ” cuttings of healthy tips, remove flowers and lower leaves . Dip the cutting in rooting hormone and insert 2″ deep in a light well drained soil. Keep cuttings in a filtered light until roots form (3-4 wks).
2. Pot them up (trim up to 1/3 ) to keep them from getting to leggy. Grow them as houseplants by placing them in the brightest window for the winter. Water when needed and fertilize once a month.
3. Store geraniums in a dormant state. Dig up the plant and place it in a papper bag with holes in it or wrap the roots in newspaper. Hang the bag in a cool, dark space (basement, crawl space).
Another old way is to hang them upside-down, bare roots in a cool, dark basement. Rehydrate the roots a few times during the winter by soaking them in water for a few hours. Pot up the plant in late winter (Feb) and resume watering. When the weather warms up place your wintered geranium outdoors .