Lemongrass (Cymbopogon citratus) is a highly aromatic, tropical, perennial grass prized globally for its culinary and medicinal uses. Native to warm regions of Southeast Asia, it is adapted to climates with year-round heat and high moisture. Gardeners must understand the USDA Plant Hardiness Zone system, which indicates the average annual minimum winter temperature for a location. This classification is crucial for lemongrass because its survival is directly tied to its sensitivity to frost.
Lemongrass Hardiness Zones and Climate Needs
Lemongrass is classified as a tender perennial, surviving the winter outdoors only in areas with little to no freezing temperatures. It is reliably perennial in USDA Hardiness Zones 10 and 11, where it grows year-round, often reaching heights of three to five feet. Its tropical nature requires a long, hot growing season to produce thick, flavorful stalks. It thrives best when temperatures consistently remain above 50°F.
The plant’s root system is intolerant of freezing conditions and typically dies back completely if exposed to temperatures below 15°F. Gardeners in Zone 9 may successfully overwinter lemongrass outdoors, but this requires significant protection, such as heavy mulching over the root crown. In these transitional zones, the foliage will likely die back completely, but protected roots may sprout again in the spring if the soil does not freeze solid.
In any zone colder than 9, lemongrass cannot be grown as a true perennial and must be treated as an annual or brought indoors for protection. This cold sensitivity is due to its origin in frost-free climates, causing the plant to cease growth and suffer damage when nighttime temperatures consistently drop below 50°F. Its success is determined by its need for a prolonged period of intense heat and sun, not its ability to withstand cold.
Optimal Growing Conditions
Lemongrass requires specific care conditions to produce robust, flavorful growth. The plant demands a location that receives at least six to eight hours of direct sunlight daily to fuel its rapid growth and maximize aromatic oils. While it appreciates heat, it benefits from protection from intense midday sun in extremely hot southern climates, as tender leaves can occasionally scorch.
The soil must be rich in organic matter and possess excellent drainage, as the plant quickly succumbs to root rot if left in standing water. A loamy or sandy structure with a slightly acidic to neutral pH (6.0 to 7.8) provides the best balance of moisture retention and aeration. Incorporating aged compost or manure before planting significantly improves fertility and the soil’s ability to hold consistent moisture.
As a fast-growing, heavy feeder, lemongrass requires consistent and abundant moisture, especially during peak summer months. Container plants may need daily watering during hot weather to prevent the soil from drying out completely. Because it is a grass, it has a high demand for nitrogen to support its dense, tall foliage, so applying a high-nitrogen or balanced liquid fertilizer every two to four weeks throughout the growing season is beneficial.
Overwintering and Container Management
Gardeners outside of Zones 10 and 11 must use container management to allow for indoor overwintering. Planting in a pot at least 12 to 14 inches in diameter or a 5-gallon size provides necessary space for the root system to develop fully. The container must have large drainage holes, and a well-draining potting mix should be used to prevent waterlogging.
Moving the plant indoors should begin before the first hard frost, typically when nighttime temperatures consistently fall below 50°F. Before relocation, the plant should be pruned dramatically, cutting the foliage back to a height of about six inches. This size reduction minimizes the plant’s moisture needs and prepares it for its winter environment.
There are two primary methods for successful overwintering: dormancy or continued active growth. For dormancy, the trimmed plant can be stored in a cool, dark location, such as a basement or garage, where temperatures are maintained between 50°F and 60°F. In this state, the plant requires only minimal, occasional watering—just enough to keep the soil from becoming bone dry—and no fertilizer.
Alternatively, the plant can be kept actively growing indoors near a bright, sunny window, ideally south-facing, or under a dedicated grow light. In a warmer environment, usually above 60°F, the plant will continue growth and need more frequent watering, allowing the top inch of soil to dry out between applications. Although winter growth is slower, this method allows for a limited harvest until the plant can be moved back outdoors after the danger of frost passes.