Liriope offers the landscaper an attractive option for a garden border with its 8- to 10-inch grass-like fronds and mounding growth habit. Killing grass invaders in a liriope bed requires examining the planting pattern as well considering the use of non-chemical means for weed removal to prevent damage to the liriope and other landscape plants. Preventive measures include mulch application and dense planting to limit the growth of unwanted grass and other weeds.
Address individual clumps of unwanted grass in the liriope bed using a shovel. Scrape away the top layers of mulch out of the general area using a hoe. Place the shovel about 2 inches from the edge of the grass clump and step down firmly on the shovel. Shove the blade 4 to 6 inches under the grass and lift up to remove the clump. Dispose of the grass in a yard waste bag.
Attack smaller clumps of grass by using a trowel to dig beneath the grass roots in tight spaces. Dig to a depth of 4 to 6 inches and remove as many roots as possible.
Edge the garden to create a trench to limit encroachment from nearby lawns. Begin on one end of the garden and step down on the shovel blade at a 30-degree angle to a 4-inch depth. Lift up the section of soil, remove grass clumps and break up the soil with the shovel. Work in a continuous line along the garden edge to form a barrier that will later be filled with mulch to further discourage grass growth.
Mulch the surface of the garden with a 3- to 4-inch layer of organic material. Mulch suppresses weeds by limiting available sunlight to fledgling weed plants.
Monitor the garden regularly to quickly kill grass as soon as it appears among the liriope. Frequent maintenance adds up to limited effort instead of the heavy weeding required in a neglected garden.