Citronella grass (Cymbopogon nardus or Cymbopogon winterianus) is a tropical, clump-forming perennial prized for its strong, lemon-like scent. This fragrance comes from essential oils within the leaves, which contain compounds like geraniol and citronellal. These oils are the source of commercial citronella products, and the plant is cultivated by home gardeners for its natural mosquito-repelling properties when the foliage is crushed. It grows as a dense, cane-like grass, reaching heights of 5 to 8 feet and a width of 3 to 5 feet. Citronella grass is native to tropical regions of Asia and is only truly perennial in USDA Hardiness Zones 10 through 12, meaning most gardeners must treat it as an annual or bring it indoors for winter protection.
Preparing the Site and Planting
The successful establishment of citronella grass begins with selecting a site that provides ample sunlight. This tropical grass thrives in full sun, requiring at least six hours of direct light daily to support vigorous growth and maximum oil production. While it can tolerate partial shade, too little light results in sparse foliage and a less robust plant.
The soil should be moist, rich, and exceptionally well-draining, as the plant will not tolerate standing water or heavy clay. Incorporating organic matter, such as compost or well-rotted manure, helps create the necessary loamy texture and fertility. If planting multiple clumps, space them approximately 2 to 3 feet apart to accommodate their mature size and allow for good air circulation.
Planting should only occur after all danger of frost has passed in the spring, typically when nighttime temperatures are consistently above 50°F. Most gardeners start with nursery plants or divisions, as growing citronella grass from seed is difficult and time-consuming. When transplanting, set the base of the clump level with the surrounding soil, then water thoroughly to settle the roots.
Routine Care for a Healthy Growing Season
Citronella grass requires consistent moisture throughout the growing season, mimicking its native tropical habitat. The soil should be kept evenly moist but never saturated, requiring regular watering, especially during high heat or drought. Applying mulch around the base helps retain soil moisture and stabilize root temperatures.
As a fast-growing, large grass, Cymbopogon species are heavy feeders and benefit from regular nutrient supplementation. During peak growing months, apply a balanced liquid fertilizer every four to six weeks to encourage thick, vibrant growth. Alternatively, a slow-release granular fertilizer or fresh compost can be worked into the soil at the beginning of the season.
The plant is generally resistant to most pests and diseases, but monitoring for common garden insects like spider mites or aphids is prudent. Pruning is mainly done for maintenance or harvesting; trim back any dead or yellowing foliage to keep the plant tidy. When harvesting leaves for their scent, use clean shears to cut the stems near the base, which stimulates new growth.
Overwintering Citronella Grass
Since citronella grass is a tropical perennial that will not survive temperatures below 32°F, gardeners in cooler climates must bring it indoors to overwinter. The transition indoors must happen well before the first hard frost, ideally when evening temperatures drop consistently below 45°F. Waiting too long can shock the plant and make adjustment to indoor conditions much harder.
If the plant is in the ground, dig it up in early autumn and pot it in a container that allows for adequate root space, using a general-purpose potting mix. Before moving it inside, inspect the plant thoroughly for pests and trim the foliage back to a height of about 3 to 6 inches. This reduction helps the plant manage the lower light conditions indoors.
During indoor dormancy, the grass needs minimal care, primarily requiring a location that receives bright light, such as a sunny south-facing window. Water should be reduced significantly, allowing the top inch or two of soil to dry out between waterings to prevent root rot. Avoid heavy fertilization during winter, only providing a light feeding if the leaves show signs of nutrient deficiency.