Geraniums are big, bold, beautiful plants that take center stage in a flower bed or patio container all summer long. Unfortunately, geraniums are tender perennials that will survive winter only in warm climates. If you live in a cold winter climate, take special steps to overwinter geraniums so they can be planted outdoors again when the weather warms up in spring.
Cut the geranium down to about 1/2 to 1/3 of its size. Check the plant carefully for signs of pests. Look on top and underneath the leaves and around the stems. If the pest infestation is minor and the geranium is healthy, remove the affected leaves. Don't attempt to overwinter damaged, unhealthy, or pest-infested plants.
Fill a large planting container with commercial potting soil. Ensure the planting container has at least one drainage hole and that it has a sturdy bottom so the geranium won't easily tip over.
Plant the geranium in the container and water immediately until the potting soil is damp. Water the geranium whenever the top of the soil feels dry to the touch.
Place the geranium in bright, indirect light. Avoid placing the plant too close to hot, sunny windows. Keep the room fairly cool, between 60 and 75 degrees F.
Pinch the tops of the stems about once a month to prevent weak, spindly growth.
Move the geranium back outdoors when you're sure the danger of frost has passed. Fertilize the geranium shortly after planting it outdoors, using a water-soluble fertilizer for blooming plants.