Apply fertilizer according to directions on the label, and make sure that the soil is moist before applying. If strong, natural light is not available in the home, artificial light is acceptable. Satisfactory results can be obtained if the plants are placed 12 inches beneath a 40-watt, daylight, cool fluorescent bulb for 16 hours each day. Temperatures during the day of 65 to 70 F and around 55 F at night are ideal. Avoid placing geraniums in cold, hot or drafty areas.
Gardeners wishing to overwinter their geraniums can try several techniques.
Before the first frost, dig large geraniums from the garden and plant in pots large enough to hold their root system. Discard any plants with evidence of insects or diseases. Cut back the top of the plant to 6 inches in height, and place in a sunny window. You can also take cuttings in the fall, and keep the small potted plants on a windowsill during the winter months. Transplant to the landscape or keep in pots once the danger of frost has passed.