Lemongrass (Cymbopogon citratus) is enjoyed as an ornamental grass for its clumping habit, fast growth rate and fragrant foliage, which turns a showy red to scarlet in fall and winter. The entire lemongrass plant can be used for cooking, so it is often a welcome addition to vegetable or herb gardens, or container plantings on decks or porches where its fragrance can be appreciated. This plant grows as a frost-tender perennial in U.S. Department of Agriculture plant hardiness zones 10 and 11, although it is kept as a container specimen or cultivated as an annual in cooler areas. If a plant in a container appears crowded, with roots growing out of drainage holes or the soil surface, or specimens in the landscape are languishing, with stalks in the center of a clump dying, transplanting is warranted.
Water the lemongrass clump or container thoroughly at least several hours before transplanting it to make the soil around the specimen easier to work with and minimize stress to the plant.
Dig a hole two to three times wider than the lemongrass clump in a spot that receives full sunlight and has well-drained soil, or place about an inch of high-quality potting soil in the bottom of a container with ample drain holes. If you are planting multiple lemongrass plants, space holes 36 to 60 inches apart.
Dig up the lemongrass clump using a sharp spade. Capture roots and soil in an area that extends about 6 inches out from the base of the plant. Alternatively, cradle the soil surface while turning the plant sideways or upside down, and slide the root mass out of the container.
Inspect the root mass. Trim off any dead, diseased or damaged roots using a sharp, clean knife. If you want to divide the clump into multiple plants, or make it smaller and discard the languishing center of the clump, use the sharp knife to cut the clump into two or more sections, each with a proportionate amount of stems and roots. If a container-grown lemongrass is root-bound, with roots growing tightly around the edge of the root mass, make four vertical, 1-inch-deep cuts evenly spaced around the root mass, and cut an "X" into the bottom of the root mass.
Set each lemongrass or new plant section in the center of a prepared planting hole or container. Check the depth of the lemongrass relative to the surrounding soil level, and add or remove soil under the roots to make sure the specimen is planted at the same depth at which it was previously grown. For container plants, the lemongrass crown and soil surface should be about 1 inch below the container's lip.
Fill in the space around the lemongrass with soil you removed when digging the hole or well-drained potting soil, if you are re-potting the lemongrass. Pat the soil down gently as you add it to force out major air pockets and reduce later settling.
Water the lemongrass in slowly and deeply to settle the soil around the roots. If the soil settled significantly, add more on top of it to achieve the correct planting depth.