In the American southeast, monkey grass is the common name for lilyturf (Liriope spicata and Liriope muscari). Used as a edging plant or as an alternative to turf grass, monkey grass grows as an herbaceous perennial within U.S. Department of Agriculture plant hardiness zones 6 to 10. Monkey grass responds best to trimming in late winter or early spring before new leaf growth starts, but can be trimmed virtually anytime during the active growing season.
You may trim monkey grass anytime it's actively growing from spring to midsummer, as it rejuvenates fully one to two months later. However, the best maintenance practice is to cut back plant clumps to 3 inches tall anytime from mid February to mid or late March, depending on latitude and climate. You want to make pruning or trimming cuts just before new leaf shoots emerge from the underground roots. Although trimming off the tips of emerging leaves isn't detrimental, it does make the monkey grass look haggard for a few weeks.
Species of monkey grass overwinter and survive as perennials in U.S. Department of Agriculture plant hardiness zones 6 through 10. Timing of trimming back plants occurs much earlier in southern latitudes and lowland elevations. In Florida, Texas or along the Gulf Coast, trim monkey grass in late February or early March. Farther north, trimming in mid to late March works well as it avoids cutting off the tips of any newly emerging leaf shoots.
Trimming Maintenance Insight
Any dead foliage that arises in monkey grass clumps during the growing season may be immediately trimmed or pull out to tidy plants. When trimming plants back in late winter, thin out dead tissues in the clump. Using your curled fingers in a claw-shaped hand, run it like a rake through the trimmed clump to remove dead leaf thatch. This increases air flow and light into the clump, reducing risk of fungal diseases and helps warm the soil to promote growth.
The monkey grass species Liriope spicata tends to developing spreading roots that sprout plantlets to form a groundcover. You can dig up or trim off these unwanted sprouts any time. Liriopre spicata and its various cultivars work well in areas you want a carpet of foliage. If you want neat clumps, more suitable to line beds or create edging, grow Liriope muscari. This species doesn't spread.