The citronella geranium, also sometimes called a "mosquito shoo" geranium in mail order plant catalogs because of its lemon scent, is from the genus pelargonium, the scented geranium family. It is categorized as an annual, but the citronella geranium can last for many years if brought indoors during winter, or by propagating the plant through cuttings you keep indoors during winter. If left outside after temperatures dip below 32 degrees F, the plant will die.
Place the citronella geranium in a pot with some commercial potting soil if it is currently in the ground.
Trim the geranium even across the top, removing approximately one-third of its height. Use small pruning shears for this and cut at a 45-degree angle above a leaf node on each stem.
Trim off any brown or diseased-looking stems and leaves.
Place the pot in a sunny location, preferably south-facing to get as much of the winter months' sun as possible, and water regularly. Indoor heating may dry the soil more frequently than the outdoor weather did.