Liriope, often called Monkey Grass, is a popular groundcover known for its tolerance to shade and drought. While attractive, certain species, particularly the aggressive, spreading Liriope spicata, can become difficult to manage once established. The plant creates a dense, fibrous root system and spreads vigorously through specialized underground stems called rhizomes, allowing it to quickly colonize large areas. Controlling Liriope requires understanding its persistent growth habits and employing tailored removal strategies.
Manual Digging and Root System Removal
Physical removal is the most direct, non-chemical way to eliminate Liriope, though it demands considerable effort. Begin by carefully loosening the soil around the patch using a sturdy spade or mattock. Dig deeply beneath the root crown to ensure the entire dense mass of the fibrous root system is lifted out intact, minimizing the chance of breaking off pieces.
Liriope’s persistence stems from its rhizomes, which can sprout new plants from small segments left behind. For the spreading variety, Liriope spicata, pay meticulous attention to tracking these underground stems away from the main clump. A thorough visual inspection of the excavated soil and surrounding area is required to find and remove all visible rhizome fragments that may lead to regrowth.
After removing the main plant mass, carefully sift the surrounding soil to eliminate any remaining root fragments. In mature, heavily infested areas, removing the top six to eight inches of contaminated soil and replacing it with clean material is often the most reliable method. This labor-intensive technique is best suited for small, contained patches or in garden beds where chemical use must be avoided.
Non-Chemical Methods Using Light Deprivation
Non-chemical removal can be achieved by completely depriving the plant of sunlight, which prevents photosynthesis and starves the root system. This smothering technique involves covering the Liriope patch with opaque materials, such as thick black plastic sheeting or several layers of heavy cardboard. The covering must extend well beyond the visible perimeter of the foliage to capture any spreading rhizomes.
For this method to succeed, the material must remain in place for an extended period, generally covering two full growing seasons (six to twelve months or longer). An alternative is soil solarization, which utilizes clear plastic sheeting instead of opaque materials. Clear plastic traps solar energy, raising the soil temperature high enough to sterilize the upper root zone.
Solarization requires high summer temperatures and direct sun exposure, typically needing six to eight weeks during the hottest part of the year. While less physically demanding than digging, both light deprivation methods demand patience and commitment to maintaining the covered area without disturbance. These approaches rely on exhausting the energy stored within the plant’s robust underground structures.
Choosing the Right Herbicides for Liriope
For large, established stands of Liriope that resist manual removal, a chemical approach using systemic, non-selective herbicides is often necessary. These chemicals, such as glyphosate, translocate throughout the plant, moving from the leaves down to the rhizomes and root crown to kill the entire structure. A primary challenge is the plant’s waxy leaf cuticle, which naturally repels water and prevents the herbicide from effectively penetrating the leaf surface.
To overcome this protective barrier, the herbicide solution must be mixed with a surfactant, often referred to as a wetting agent. The surfactant reduces the surface tension of the spray, allowing the chemical droplets to spread out and adhere to the waxy leaves, improving absorption. Repeated applications are commonly required because Liriope’s dense growth often shields underlying leaves, preventing uniform coverage in a single treatment.
Application timing is important for success, as systemic herbicides work best when Liriope is actively growing and translocating nutrients to its roots, typically during spring and early fall. The plant should not be recently mowed or cut before treatment, as maximum leaf surface area is required for optimal chemical uptake. Safety precautions, including wearing gloves, long sleeves, and eye protection, must be followed when mixing and applying any chemical solution.
Because glyphosate is non-selective, it will damage or kill any desirable plant material it contacts, necessitating careful, spot-treatment application. Following the initial treatment, foliage may take seven to fourteen days to show signs of decline. A second application is usually needed once new sprouts emerge from surviving rhizomes to ensure that sections that escaped the first treatment are targeted before they can re-establish.
Preventing Regrowth and Proper Disposal
Proper disposal of Liriope material is necessary to prevent re-infestation. The dense root crowns and rhizomes remain viable for a long time, so they should never be added to a home compost pile or left on the ground. All removed plant debris must be bagged and disposed of as municipal yard waste or allowed to dry out completely on a paved surface before disposal.
Following the main removal effort, continuous monitoring of the area is required for at least one full growing season. Any new sprouts must be immediately spot-treated with manual removal or a targeted herbicide application to eliminate surviving root segments. If replacing Liriope with new plantings near the treated area, installing a physical root barrier can help prevent stray, deep rhizomes from re-establishing the plant.