How to Trim Liriope

When the turfgrass lawns all around it lie exhausted and brown in the summer heat, the narrow, arching, green foliage of liriope (Liriope muscari) keeps its cool. Perennial liriope, also known as lilyturf, isn't grass. In mass plantings, however, it forms a lush ground cover, with the late-summer bonus of lavender flower spikes.

Although marketed as an evergreen that is perennial in U.S. Department of Agriculture plant hardiness zones 5 through 10, lilyturf may develop brown, withered foliage during winter in some areas. That is most likely to occur when temperatures drop below minus 10 degrees Fahrenheit.

Deep cold isn't lilyturf's only enemy. In all climates, the fungal disease anthracnose may leave the plant brown and tattered. Whether cold or disease is the problem, a well-timed trim is the solution.

Don't confuse clump-forming liriope (Liriope muscari) with the related creeping lilyturf (Liriope spicata), which is hardy in USDA zones 4 though 10. Although both plants spread by underground roots or runners called stolons, and are considered invasive in some parts of their growing ranges, creeping lilyturf is the more aggressive plant.

Pruning doesn't control out-of-bounds lilyturf plants; only digging up and discarding them or spraying them with root-killing glyphosate or diquat herbicide does. Herbicide use requires repeat treatments and shielding nearby plants from the drifting spray.

The best time to trim lilyturf's damaged old foliage is anytime before its healthy new foliage emerges in spring. Otherwise, you'll shave the top of the fresh growth as well as the old growth. Fall trimming of anthracnose-blemished plants -- in warm-winter climates, at least -- keeps them looking good until spring.

Cutting back cold-damaged foliage can wait until anytime between January and April, depending on when the threat of subzero temperatures subsides in your area.

Trim a large lilyturf planting with a lawn mower; for edgings or border-accent plants, hedge trimmers are easier to manage. Hedge trimmers are also better for cutting lilyturf with sprouting leaves because the tool can cut just above the new growth.

For simple, even cutting, sharpen the lawn mower's or trimmers' blades before you begin.

Before mowing lilyturf, adjust the mower blades to their highest setting.

The most important factor is to keep the lawn mower blades high enough to protect each lilyturf's crown, which is the part just above the soil line and from where new leaves emerge. Setting the blades to cut 3 to 4 inches high should keep the crowns safe.

Use the hedge trimmers like a giant pair of scissors. Kneeling, hold the trimmer grips firmly, and slide the blades into the foliage 3 to 4 inches above the crowns. As you cut, keep the blades horizontal and parallel to the ground. Otherwise, the trimmed plants will look uneven and spiky.

Keep anthracnose from spreading by washing the mower or trimmer blades in a solution of 1 part household bleach to 9 parts water before using them on healthy plants.

After trimming anthracnose-infected lilyturf, rake up as much of the old foliage as possible, and dispose of it in sealed plastic bags. The removed foliage harbors spores that can reinfect the plants during wet weather.