Lemongrass (Cymbopogon citratus or Cymbopogon flexuosus) is a fast-growing, tropical perennial plant. Native to South Asia, this aromatic grass is prized globally for its citrusy scent and flavor in both culinary and essential oil applications. It grows in dense, grassy clumps, featuring long, slender, arching leaves. Understanding its natural growth limits and how cultivation practices affect its size is important for gardeners.
Typical Mature Height and Spread
Under ideal, tropical conditions, mature lemongrass generally reaches a height between 3 and 6 feet (0.9 to 1.8 meters). This measurement refers to the top of the tall, arching foliage, which gives the plant an ornamental, fountain-like appearance. The plant spreads significantly, forming dense clumps 2 to 4 feet (0.6 to 1.2 meters) wide as they multiply through underground rhizomes.
The edible stalks harvested for cooking are cut from the base of this large clump. While the plant can occasionally produce a flowering stalk, this is uncommon outside of its native tropical habitat. For most gardeners growing lemongrass as an annual, the maximum height usually falls between 3 and 5 feet, depending entirely on the environmental conditions provided.
Environmental Factors Influencing Growth
The final size of a lemongrass plant is significantly determined by the external environment, particularly warmth and light. As a tropical species, it requires temperatures ranging from 70°F to 100°F (21°C to 38°C) for maximum growth. Exposure to temperatures below 50°F (10°C) will quickly stunt development, and frost will typically cause the plant to die back.
Lemongrass needs abundant sunlight to support vigorous vertical growth. A location receiving at least six hours of direct sunlight daily is necessary to achieve the tallest, most robust stalks. Plants grown in partial shade often exhibit reduced vigor, resulting in leggy growth and a lower overall height. Consistent moisture levels and high humidity are also necessary to mimic its native habitat.
The quality of the soil also supports a large, dense clump. Lemongrass thrives in well-drained, fertile, loamy soil rich in organic matter. Soil that is consistently moist but never waterlogged provides the necessary foundation for the plant to achieve its maximum potential height and spread. Providing a nutrient-rich environment allows the plant to build the strong root system needed to support its foliage.
Managing Size Through Cultivation
Gardeners frequently use specific cultivation methods to control the size of lemongrass, particularly when growing it in non-tropical zones.
Container Growing
Growing the plant in a container is the most effective way to restrict its overall size. Confining the root system within a pot, ideally at least 12 inches wide and deep, naturally limits how tall and wide the dense clump can become.
Regular Harvesting
Regular harvesting of the outer stalks functions as a method of size management and pruning. By cutting or pulling the mature stalks near the base of the plant, the overall density is reduced, preventing the clump from expanding beyond a manageable footprint. This practice encourages the plant to produce new shoots.
Dividing Clumps
For plants grown directly in the ground, dividing the clumps is an important technique for managing both size and health. Splitting the overgrown clump in the spring prevents it from reaching its maximum potential spread. This process involves separating the plant into smaller sections, each with its own root system, which keeps the overall footprint manageable.