Lemongrass (Cymbopogon citratus or C. flexuosus) is a large, aromatic perennial grass native to South and Southeast Asia. This tropical herb is known for being fast-growing, but its final size depends heavily on the climate. When grown year-round in warm regions, it reaches its maximum potential; in cooler areas, it is treated as a seasonal annual, limiting its growth.
Maximum Size and Growth Habit
When grown as a perennial in tropical or subtropical environments (USDA Zones 9-11), lemongrass reaches its full potential size. Mature clumps in ideal conditions often stand between five and seven feet tall, sometimes reaching six feet in diameter. This substantial growth occurs because the plant develops continuously over multiple seasons without being cut back by frost.
The plant naturally grows in a dense, non-invasive clumping habit, forming a thick tussock from a central root crown. The long, strap-like leaves arch gracefully. In temperate regions, where it is cultivated as an annual, the plant’s size is significantly restricted. Lemongrass usually matures to a height of three to four feet and a spread of two to three feet before the first frost requires harvest.
Key Factors Influencing Growth
The size a lemongrass plant achieves is directly tied to the length of its growing season and available resources. As a tropical plant, it requires a minimum of six to eight hours of direct sunlight daily to fuel rapid growth. Lemongrass thrives best when soil temperatures are warm and consistent, with growth accelerating after the heat of summer arrives.
Lemongrass is a heavy feeder and moisture-loving, requiring consistently moist, rich, well-draining soil to support its large biomass. A lack of adequate water, sun, or nutrients will result in thinner stalks and a smaller overall footprint. Temperature is the overriding factor, as the plant is not frost-tolerant and will die back when temperatures drop below freezing.
Managing Lemongrass Size
Gardeners have two primary methods for actively controlling the size of a lemongrass plant. Growing the plant in a container is the simplest way to restrict its size, as the pot naturally limits root expansion. Use a container that is at least 12 inches across, and be prepared to move it to a larger size as the roots become crowded.
The second management technique is consistent harvesting and pruning. Lemongrass responds well to being cut back, and frequent harvesting of the outer stalks encourages new growth. Removing the oldest, most mature stalks helps maintain the clump’s size and prevents the plant from becoming woody. The entire clump can also be dug up and divided every few years, which rejuvenates the plant.