Lemongrass (Cymbopogon citratus) is a tropical perennial grass cultivated globally for its distinct citrus aroma and flavor, used in both culinary and ornamental applications. As a vigorous clumping plant, it requires periodic cutting back to maintain a manageable size and ensure the production of tender, flavorful new stalks. Pruning not only prevents the plant from becoming woody and overgrown but also redirects the plant’s energy toward stimulating fresh, robust growth from the base. The timing of this cutback is highly dependent on the plant’s growth cycle and the local climate.
Seasonal Timing for Major Rejuvenation
The most significant cutback, known as rejuvenation pruning, should occur just before the plant breaks dormancy and begins its active growth phase. This timing generally falls during late winter or very early spring, after the most severe threat of frost has passed. Waiting until this point ensures that any new growth stimulated by the pruning will not be damaged by freezing temperatures.
The primary goal of this annual cut is to remove the majority of old foliage, directing the plant’s energy into developing new, thick stalks. To achieve this, the entire clump should be trimmed back drastically, removing approximately two-thirds to three-quarters of the overall height. Gardeners often cut the foliage down to about 6 to 12 inches from the ground, or right down to the tender, pale white part of the stalk.
This severe trimming encourages the plant to focus its resources on its root system and the crown, promoting a flush of vibrant, new shoots. This is also the ideal time to remove any accumulated dead leaves and overly thick, woody outer stalks. Using sharp pruning shears ensures clean cuts that minimize stress on the plant.
Routine Maintenance and Harvesting Cuts
Throughout the active summer growing season, cutting back lemongrass shifts from a major event to routine, selective maintenance and harvesting. Harvesting stalks for culinary use provides a continuous, light pruning that helps keep the clump in check and encourages further production. The most flavorful and tender part of the plant is the lower portion of the stalk, closest to the root.
When harvesting, select individual stalks that are at least one-half inch thick and cut them as close to the soil line as possible. Removing the entire stalk near the base, rather than simply trimming the leaf tips, is the correct technique to obtain the aromatic section used in cooking. Cutting from the outer edges of the clump allows the younger, central stalks to mature.
Routine maintenance also involves removing any stalks that naturally turn brown or yellow. These older, discolored stalks should be clipped at the base to improve airflow within the clump. Improved airflow helps prevent fungal issues like rust, keeping the plant healthy and continuously producing fresh growth.
End-of-Season Preparation for Cold Climates
For gardeners in colder climates, where lemongrass is not hardy and is grown as an annual or overwintered indoors, the cutback timing is determined by the first autumn frost. In regions with freezing winters, the plant must be prepared for protection in late fall, typically before temperatures consistently drop below 40 degrees Fahrenheit.
To prepare a clump for overwintering indoors, the foliage should be cut back significantly to make the plant manageable. Trimming the stalks down to approximately 6 inches in height allows for easier digging and potting of the root ball or rhizome mass. Once cut back, the plant can be potted and moved to a cool, dark location, such as a garage or basement, where it will go dormant for the winter.
If the plant is to be left outdoors in a marginal zone (such as USDA Zones 8–9), the entire plant should be cut back to just a few inches from the ground. This cut is followed by applying a thick layer of insulating mulch over the crown to protect the rhizomes from freezing temperatures. This late-season cut is a practical measure to prepare the plant for dormancy or storage.