Citronella grass (Cymbopogon nardus), a clumping, tropical grass, is known for its essential oil, which is used in everything from lotion to candles to help ward off mosquitoes. Citronella may grow up to 6 feet tall, producing canelike stems and long green leaves that give off a strong aroma. Citronella is fairly low maintenance, though it will only survive the winters in the warmest climates.
A native of southeast Asia, citronella grows outdoors only in U.S. Department of Agriculture plant hardiness zones 10 through 12. The grass doesn't tolerate shade, requiring a bright, sunny spot to thrive. Where not hardy, you can grow citronella as an annual or dig it up in fall, plant it in a pot and keep it indoors until temperatures have warmed in spring. You can also grow it in a container year-round and move it indoors as needed.
Citronella is durable and adaptable, and will grow in a range of soil types. It does best in a well-draining, fertile soil. Grasses in general require high amounts of nitrogen, so fertilize your citronella plant with a balanced 20-20-20, water-soluble fertilizer, diluted at half strength. This is usually 1/2 tablespoon per 1 gallon of water, but check the label on the fertilizer you buy. Mail order nursery company White Flower Farm recommends applying fertilizer once a month during the growing season for plants in the ground, and every two weeks for container plants. Provide at least 3 feet of space between each plant.
Remove weeds periodically and water frequently throughout the growing season to keep the soil moist, but not waterlogged or flooded. Citronella requires at least 30 inches of water each year. Indoor plants are more susceptible to spider mites, which can cause yellow stippled dots on the leaves. Spray the plant with a strong stream of water to remove mites. Citronella is easy to propagate by division. Divide the clumps in late fall and pot up smaller divisions to keep warm near a sunny indoor window.
Though citronella is closely related to lemongrass (Cymbopogon citratus), which grows in USDA zones 9 through 10, you can't use citronella for cooking. Citronella may repel cats from the garden, notes Floridata. Although citronella can be rubbed on the skin to prevent mosquito bites, the oil is only effective for 30 to 40 minutes and may cause skin irritation or dermatitis. Some people experience an increased heart rate from inhaling the oil from the grass.