Lemongrass (Cymbopogon citratus) is a tropical, clumping perennial grass prized globally for its distinct lemon aroma and flavor. Originating in warm regions of South Asia, it is characterized by tall, slender, arching foliage. It grows in dense tufts using an aggressive system of underground rhizomes that continually sprout new stalks. Its perennial nature in warm climates allows it to develop into a substantial, fountain-like specimen.
Maximum Size Potential: Height and Clump Width
Under ideal, tropical growing conditions, lemongrass develops into an imposing, architectural grass. The typical mature height for a healthy, established clump ranges from 3 to 5 feet, though some specimens can reach 6 feet or more. This height is measured to the tip of the arching leaf blades, which form a dense fountain of foliage.
The width of the clump reflects the plant’s aggressive rhizome system, which spreads horizontally beneath the soil. In a perennial environment, the diameter of a mature clump usually spans between 2 to 3 feet, creating a dense, bushy mass. If left undivided for many years, these clumps can spread further, sometimes reaching up to 6 feet in diameter.
The overall size of the foliage should be distinguished from the usable culinary portion of the plant. The base of the lemongrass, where the stalks swell to form the tender, white culms used in cooking, is relatively small compared to the plant’s overall footprint. Stalks are ready for harvest when they reach approximately half an inch in diameter near the soil line. The plant’s size potential is determined by the extensive network of roots and rhizomes that fuel its rapid, dense growth.
Key Environmental Factors Influencing Growth
The size a lemongrass plant achieves depends highly on environmental inputs, particularly temperature and light exposure. As a tropical perennial, the plant thrives in consistent warmth, preferring temperatures between 70°F and 85°F. In cooler climates, growth is severely limited, as the plant is often treated as an annual killed by frost, preventing it from reaching maximum perennial size.
Sunlight is another determining factor, requiring full sun exposure—a minimum of six to eight hours of direct light daily—to achieve maximum height and density. Plants receiving less light, such as those grown in partial shade, will exhibit stunted growth, resulting in thinner, paler stalks and a less vigorous clump. Insufficient light directly impacts the plant’s ability to photosynthesize enough energy to support a large stature.
Consistent moisture is necessary to fuel the plant’s rapid growth rate and reach its full size potential. Lemongrass is not drought-tolerant and requires regular watering throughout the growing season to keep the soil moist. A rich, fertile, and well-draining soil is also needed, as the plant is a heavy feeder that requires ample nutrition to support its large biomass.
Managing Size Through Cultivation and Harvest
Gardeners outside of perennial zones often manage the plant’s size by growing it in containers. Planting lemongrass in a pot, such as a 5-gallon size or one at least 12 inches deep and wide, naturally restricts the growth of the root system. This root restriction limits the overall height and clump width, allowing the plant to remain a manageable size for overwintering indoors.
Regular harvesting of the outer stalks acts as a form of size control and encourages the development of new shoots. By removing individual mature stalks from the edge of the clump, the plant is prevented from aggressively expanding its diameter. This practice maintains a more compact base while allowing the central portion of the clump to continue generating new growth.
For established, in-ground clumps in perennial climates, physical intervention is necessary to prevent excessive size. Dividing the clump every few years rejuvenates the plant, prevents overcrowding, and controls the width expansion caused by the rhizomes. The foliage can also be cut back hard, often sheared down to about six inches in late winter or early spring, to maintain a manageable height and encourage a fresh flush of growth.