Geraniums grown indoors present a new set of challenges to the home gardener. Providing adequate light is essential for flowering, as well as providing the right amount of water and fertilizer for successful container culture. Planted in window boxes, decorative planters or hanging baskets, geraniums flower all year with proper care and attention. Purchase healthy plants from local nurseries or garden centers in spring and summer. Numerous geranium cultivars are available during this time and all require similar care to thrive indoors.
Keep geraniums in a location that receives six to eight hours of direct sunlight each day to encourage flowering. Maintain a temperature of 65 to 70 degrees F during the day and 55 to 60 degrees F at night.
Water geraniums only when the top 4 to 6 inches of soil are completely dry, about once every 10 days. Do not over-water geraniums, as they prefer the soil slightly on the dry side. Reduce frequency of watering to once every two weeks during winter.
Feed twice per month from March to October with a water-soluble houseplant fertilizer. Fertilize at the rate recommended by the manufacturer's directions for the best results. Reduce feeding to once per month for geraniums grown in low light.
Prune indoor geraniums during late winter before active growth resumes in spring. Cut off long or damaged limbs with pruning shears to improve the appearance of the plant and encourage a thicker growth habit.
Repot geraniums once every four years to provide additional room for growth and a fresh growing medium. Increase the size of the pot by about 2 inches each time, and use a growing medium made of one part garden loam, one part peat moss and one part perlite.