Cymbopogon nardus, commonly known as Citronella Grass, is a tropical, clump-forming perennial prized for its bright lemon-citrus fragrance. This tall, ornamental grass features long, slender, arching leaves that can reach heights of five to eight feet. The essential oil derived from its foliage is widely recognized for its natural insect-repelling properties, particularly against mosquitoes. Native to tropical Asia, the grass is cultivated globally for its aroma and functional use in outdoor spaces.
Site Selection and Soil Preparation
Citronella Grass thrives best in full sun exposure throughout the day. Although it can tolerate partial shade, insufficient sunlight results in spindly growth and may reduce the concentration of aromatic oils. Since this is a tropical species, it is only reliably perennial in USDA Hardiness Zones 10 through 12, where temperatures rarely drop below freezing.
Gardeners in cooler climates must treat C. nardus as an annual or grow it in containers that can be moved indoors. The soil must be consistently moist yet have excellent drainage. A rich, loamy, or sandy soil texture amended with organic matter is ideal for healthy root development.
The plant prefers a soil pH that is slightly acidic to neutral, generally falling within the 5.1 to 7.5 range. Excessive water retention causes the grass to decline and succumb to root rot. Preparing the planting site with compost or well-aged manure helps establish the necessary moisture retention and nutritional foundation.
Planting, Watering, and Fertilization
Citronella Grass is commonly started from root divisions, though propagation from seeds or stem cuttings is also possible. When planting directly into the ground, clumps should be spaced approximately 24 to 36 inches apart. For container growing, select a pot with a minimum diameter of 12 inches to allow for the extensive root system and rapid growth rate.
Consistent moisture is necessary for robust growth, especially during hot, dry weather. Water deeply whenever the top inch of soil feels dry to the touch, keeping the soil evenly damp without allowing it to become waterlogged. Drought conditions can cause the foliage to yellow and the plant to enter premature dormancy.
This fast-growing grass benefits from regular feeding. Potted plants require more frequent nutrient input than those in the ground, typically a weekly application of a balanced liquid fertilizer during the peak growing months. A formula such as a 10-10-10 or 20-20-20 provides the necessary nitrogen, phosphorus, and potassium.
Seasonal Pruning and Overwintering
Pruning is used to remove spent leaves and encourage fresh growth. Throughout the growing season, remove any dead or yellowing outer stalks by cutting them close to the base of the plant. A more severe pruning, often referred to as “scalping,” is best performed in the early spring before new growth begins, cutting the entire clump back to within a few inches of the ground.
For those in non-tropical climates, overwintering is necessary to keep the perennial alive. Container-grown plants should be moved indoors before the first expected frost, as the roots cannot tolerate temperatures below 32°F. Before moving the pot inside, cut the foliage back severely to a height of six to twelve inches to make the plant more manageable.
Once indoors, the plant enters a period of semi-dormancy and requires reduced watering, only needing moisture when the soil is completely dry. Provide the plant with bright light, ideally from a south-facing window or supplemented with a grow light, until spring temperatures are consistently above 50°F. In marginal zones like 8b or 9, heavy mulching with straw or a frost blanket may allow established clumps in the ground to survive; the brown, dead foliage should be cut back in the spring.
Harvesting and Using Citronella Grass
Harvesting the aromatic leaves of Cymbopogon nardus is best done once the plant is well-established, often in its second year of growth. The foliage contains the highest concentration of essential oils, so focus on cutting the mature outer stalks. Use a sharp, sterile tool to make clean cuts near the base, taking care to leave the inner sheaths intact since they contain less potent oil.
Harvesting before the plant begins to flower maximizes the oil content, producing the most fragrant material. The fresh leaves can be lightly crushed and rubbed onto the skin to release their natural lemon-scent as a temporary insect deterrent. For long-term use, the harvested material can be dried and used in potpourri, or steeped to create a base for homemade insect repellent sprays.