Citronella geranium, also called mosquito plant, can tolerate relatively dry soil and needs about 6 hours of sunlight every day. While it can withstand partial shade, the plant stretches and falls over if it doesn't get enough sun. Citronella can live in many well-drained soils, but grows best in moderately rich, moderately moist soil. To encourage new growth, prune citronella by pinching it back.
Citronella is hardy in temperate zones 9-11, even outside in the summer. Stems can also get woody during summer, but layering by bending a stem and sticking it into the soil of a new pot can grow a new plant. Bring plants inside before the first frost of the year, as citronella is sensitive to cold. In warmer areas, established, pruned plants can overwinter outside. Citronella grows well indoors as long as it gets enough sun and water. Indoor plants need only occasional feeding with an all-purpose plant food.
Expect lavender blooms and a light fragrance that complements the scents of other flowers during the summer. Although its common name is mosquito plant, there is some debate about the ability of citronella to repel mosquitoes. There is some evidence, however, that rubbing crushed leaves on the skin may keep mosquitoes away.
As long as it is well-draining, citronella plants can tolerate most soils. About.com recommends using a soil that is not too rich, as rich soil can decrease the plant's citrus scent. Scented geraniums like citronella are tolerant to drought and should not sit in wet soil for too long. The plant needs watering when the soil feels dry an inch below the surface. If the leaves turn yellow or brown and fall off, the plant is not receiving enough water.
During the winter, citronella does not require fertilizer. Potted citronella plants require more fertilizer than citronella in the ground. Feed potted citronella a balanced fertilizer at half of the label's recommended dilution. This can be done in the spring and summer, once a month, or as needed according to visual assumptions. For fuller, bushier plants, try pruning and pinching them on occasion. The spring months are the best for pruning.