Lemongrass (Cymbopogon citratus) is a popular tropical perennial grass valued for its distinct citrus aroma in culinary and ornamental applications. Maintaining a productive and healthy plant requires specific, ongoing care tailored to its tropical origin. Successful long-term cultivation depends on providing the correct environment, managing inputs, structurally rejuvenating the plant, and preparing it for non-native climates. This guide focuses on the routine maintenance required for a vigorous and abundant yield.
Essential Environmental Requirements
Lemongrass requires warmth and abundant light to support its rapid growth. The plant thrives best in full sun, needing a minimum of six to eight hours of direct, unobstructed sunlight daily. Insufficient light leads to weak, spindly stalks and reduces the aromatic oils that give the herb its flavor.
As a tropical species, lemongrass is sensitive to cold; growth slows or halts below 50°F. The optimal temperature range for robust growth is consistently between 70°F and 95°F. In regions where temperatures fall outside this range, container planting allows for necessary seasonal relocation.
The proper growing medium is important, as this herb does not tolerate saturated conditions. Lemongrass requires fertile, well-draining soil rich in organic matter to support its heavy feeding nature. An ideal soil pH is slightly acidic to neutral (6.0 to 7.0), which facilitates optimal nutrient uptake.
Hydration and Nutrient Management
Consistent moisture is necessary to fuel the rapid production of new stalks and foliage during the active growing season. The soil should be kept uniformly moist but never soggy, achieved by watering deeply whenever the top inch of the soil feels dry to the touch. Waterlogged soil quickly leads to root rot, which is a common cause of failure in container-grown plants.
Lemongrass is a heavy feeder and consumes nutrients quickly. Regular fertilization is required to maintain its deep green color and robust structure. In-ground plants benefit from a bi-weekly application of a balanced, water-soluble fertilizer during the spring and summer.
For container plants, increasing the frequency to a weekly or bi-weekly application is often necessary. The plant responds well to high-nitrogen formulas (e.g., NPK ratio around 10-6-4), as nitrogen supports green, leafy growth. Yellowing of older, lower leaves indicates a need for increased nitrogen input.
Structural Maintenance Through Pruning
Pruning encourages new growth and prevents the plant from becoming an overcrowded, unproductive clump. Basic maintenance involves regularly removing dead or yellowing outer leaves, which improves air circulation within the dense clump. Cut this foliage cleanly back to the base of the stalk.
Harvesting stalks also serves as maintenance pruning, stimulating the plant to produce new shoots from the center. Stalks ready for harvest are typically at least a half-inch thick and should be pulled or cut from the outside of the clump. Removing only the mature outer stalks allows the younger, inner growth to continue developing.
A hard prune should be performed annually in early spring for comprehensive structural rejuvenation. This involves cutting the entire plant back dramatically, leaving only a few inches of stubble above the tender white base of the stalk. This removes old, woody material and focuses the plant’s energy on developing a fresh flush of robust, flavorful stalks.
The clumping habit of lemongrass necessitates periodic division to prevent overcrowding. When the clump becomes too dense or pot-bound (typically every two to three years), the entire plant should be dug up and separated. Dividing the root mass into smaller sections, each containing several stalks, allows for better nutrient access and prevents the plant from exhausting its growing medium.
Preparing Lemongrass for Winter Survival
Lemongrass is a tender perennial that only survives year-round outdoors in USDA Hardiness Zones 9 through 11, where frost is not a threat. In colder climates, the plant must transition indoors before the first expected frost, as temperatures below 40°F cause significant damage. Container-grown plants are moved inside, while in-ground plants must be dug up, divided, and potted for the winter. Preparing the plant involves a substantial haircut, cutting the foliage back to six to twelve inches. This reduction helps the plant conserve energy and reduces moisture loss indoors. The roots should be placed in a pot with drainage holes and fresh potting soil. Once indoors, there are two main strategies for survival.
Dormant Storage
The plant can be stored in a cool, dark location (50°F to 60°F), such as a garage or basement, for a near-dormant state. Watering should be drastically reduced, providing small amounts of water only once a month to prevent the roots from completely drying out.
Active Indoor Growth
If a bright, south-facing window is available, the plant can continue slow growth indoors. It should receive at least six hours of light daily and be watered when the top inch of soil is dry. Fertilizer application must be discontinued until spring. The plant is then gradually reintroduced to outdoor conditions once all danger of frost has passed.