The citronella mosquito plant (Pelargonium citrosum), a hybrid member of the geranium family (Pelargonium spp.), is perennial in U.S. Department of Agriculture plant hardiness zones 9 through 11 and grown as an annual elsewhere. Delicate pink flowers and lacy, lemon-scented leaves make the plant an attractive and aromatic addition to borders and mixed container displays. It can also be grown as a houseplant, but be aware that its leaves may be mildly toxic to pets.
Set plants out in spring after the danger of frost has passed, if applicable. If planting directly into the ground, choose a site with organically rich and moist but well-drained soil that receives a few hours of afternoon shade, spacing plants 18 to 24 inches apart. When planting in containers, be sure drain holes exist to permit excess water to escape. Clay pots are preferable to plastic because they encourage water evaporation.
In USDA zones below 9, bring plants indoors when nighttime temperatures fall below 40 degrees Fahrenheit and place where they will get at least four hours of sunlight and remain free of cold drafts. Plants require less water indoors over the winter, so let the soil dry out a bit between waterings. In spring, after the last frost has passed, place plants outside for a few hours a day to "harden off" before transplanting to new outdoor containers or back to the garden.
Like other geraniums, the citronella mosquito plant displays well in a variety of settings. In this case, however, its dramatic leaves rather than the small flowers draw the eye, so consider this when selecting a site. Also, because its leaves are aromatic, strategically positioning plants where they may be brushed against or touched, such as along a walkway or on a deck railing, will promote the release of their scent. Other suitable places include window boxes, hanging baskets or grouped in flower gardens.
Although this species is referred to as "citronella mosquito plant," it shouldn't be confused with "true" citronella (Cymbopogon nardus), a perennial grass in USDA zones 10 through 12 that contains similar aromatic compounds but is unrelated. Similarly, despite being marketed as a natural insect repellent for the deck or yard, the mosquito plant does not effectively repel mosquitoes.