Geranium plants can be started from cuttings to make new plants. You do need to take cuttings before the first frost and prepare the stems for rooting. The geranium stems will root and make a new plant if you use the correct rooting mixture and prepare the container correctly. There are a few thing to do to a geranium that you might not do for another type of plant.
Snip off a plant stem before the first frost. The stem should be 3 to 4 inches long. Use a knife or scissors to remove the bottom leaves from the stem that will be placed in the rooting mixture.
Use a potting mixture with equal parts of peat moss and coarse sand. Place the mixture in containers that are at least 4 inches deep with drainage holes on the bottom.
Apply a root hormone to the bottom of the stems. Plant the cutting in the rooting mixture at least 1 to 2 inches deep. Water the rooting mixture thoroughly. Cover the stem and pot with a plastic bag. Do not seal, just place the bag loosely over the plant.
Place the plant in a bright location, but not in direct sunlight. The rooting mixture can dry between waterings. The stem should have roots in three to four weeks at which time you can remove the plastic covering.
Place the container in a sunny location and water as needed. The geranium will need at least four hours of sun a day to flower. Add 5-5-5 fertilizer to the geranium. Pinch off tips of the stems to prevent long spindly stems until the plant is fully developed and ready to go outdoors when all signs of frost have passed.