Lemongrass (Cymbopogon citratus) enters dormancy when temperatures start to dip below 45°F.
The best time to cut back your lemongrass is while it’s dormant, but not until temperatures start to warm up in spring. This can be anywhere from late February to late April, depending on your climate.
Nighttime temperatures should stay consistently in the mid-40°Fs for lemongrass to successfully bounce back from an early-season trim.
If you’re in zones 8b to 9, your job is easy: simply pull back the frost blanket (or mulch) and cut down the entire plant to just a couple inches above the tender white part of the stalk, removing all the brown leaves.
Gardeners whose plants stay green all winter just need to maintain the shape of the shrub. Light pruning of the leaf tips can be done throughout the year, but a heavy pruning should be done in spring to give your lemongrass a chance to grow stronger and healthier.