Lemongrass needs to be cut back to 2 to 4 inches above the base before winter, whether you’re bringing it indoors or leaving it in the ground with protection. The timing depends on your climate zone, but the goal is the same: remove the tall, leafy growth so the plant can survive dormancy and push out fresh shoots in spring.
Know Your Zone First
How aggressively you need to intervene depends on where you live. Lemongrass is a tropical plant that stays evergreen year-round only in USDA Zones 10 and 11. In those warm climates, winter pruning is optional and mostly cosmetic. The roots can survive outdoors down to Zone 8b, but the foliage will turn completely brown and look dead after frost. Below Zone 8, lemongrass freezes to death when temperatures drop below 15°F, so you’ll need to dig it up and move it inside.
If you’re in Zones 8b or 9, your lemongrass can stay in the ground with heavy mulching. In Zones 7 and colder, plan to dig up at least a few stalks and pot them for indoor storage. Either way, pruning is the first step.
When to Prune
The best window is late summer through early fall, before your first frost. Lemongrass has zero tolerance for freezing temperatures, so don’t wait until the leaves are already damaged. If you’re digging stalks up to bring inside, do it while the plant is still healthy and green. You can also wait until early spring to do a hard cutback if you have the indoor space to store a larger plant over winter, but most people prefer to trim in autumn to keep things compact.
How to Cut Back Lemongrass
Wear thick gloves. Lemongrass leaves have razor-sharp edges that will slice unprotected skin. Heavy-duty garden gloves or leather work gloves are worth the trouble. Use sharp hedge shears, loppers, or a serrated knife for the thicker stalks near the base.
Cut all the foliage down to 2 to 4 inches above the base of the plant. You’re removing the long, grassy leaves entirely and leaving just short stubs above the white, fleshy part of the stalk. Don’t cut into the white section itself, as that’s where new growth will emerge in spring. For a large clump, it helps to gather the leaves into a bundle with one hand (or tie them with twine) and cut across the whole mass at once.
If your lemongrass is already brown from a light frost in Zones 8b or 9, the process is the same. Pull back any frost blanket or mulch, cut the entire plant down to a couple of inches above the white stalk, and remove all the dead brown leaves.
Overwintering in the Ground (Zones 8b to 9)
After cutting back, pile 4 to 6 inches of mulch over the crown of the plant. Straw, shredded leaves, or wood chips all work. This insulates the roots through cold snaps. The top growth will die back completely and look lifeless all winter, but the root system stays viable underground as long as the soil doesn’t freeze solid for extended periods. Pull the mulch back in spring once nighttime temperatures are consistently above freezing.
Bringing Lemongrass Indoors (Zones 7 and Colder)
Dig up a few outer stalks from the clump, keeping some roots attached. Trim the leaves down to 2 to 4 inches and plant each division in a small pot with standard potting mix. You don’t need to save the entire clump. Two or three healthy divisions are enough to restart your patch next year.
You have two options for where to keep them. The first is a bright, south-facing window that gets at least 6 hours of light. A supplemental grow light helps if your winter days are short or overcast. Plants stored this way will stay alive but grow very slowly. Keep the soil barely moist, not wet. Overwatering dormant lemongrass is the fastest way to kill it, since the roots aren’t actively drinking. Check the soil every week or so and water only when the top inch feels dry.
The second option is cold storage in a cool, dark place like a basement or unheated garage that stays above freezing. Cut the stalks down, pot them, water lightly once, and leave them alone. The plant goes fully dormant this way. You’ll water maybe once a month, just enough to keep the roots from completely drying out. This method takes up less space and requires less attention, but the plants will be slower to wake up in spring.
Dividing Large Clumps
Winter pruning is a natural time to divide an overgrown lemongrass plant. A healthy clump can spread to several feet wide in a single season, and splitting it keeps the plant manageable while giving you extra starts. Separate sections from the outer edge of the clump, making sure each division has its own root system attached. Pot each one individually. If your plant is still relatively small (first-year growth), skip the division and just prune it back whole.
What to Expect in Spring
Lemongrass is notoriously slow to start in spring. Don’t panic if your pruned stubs sit there doing nothing for weeks after the weather warms up. New growth won’t appear until temperatures are consistently warm, and the plant really takes off only once summer heat arrives. If you overwintered indoors, wait until after your last frost date to move pots back outside or transplant divisions into the garden.
To check whether a dormant plant is alive or dead, look at the base of the stalks. If the inner core is still white or pale green and firm when you peel back the outer layers, the plant is viable. If it’s brown, mushy, or hollow all the way through, it didn’t make it. Healthy dormant lemongrass feels solid at the base even when every visible leaf is brown and dry.