Monkey grass (Liriope and Ophiopogon) is a popular choice for groundcover due to its hardiness. However, spreading varieties can quickly become an invasive problem in garden beds and lawns. Complete eradication requires a persistent, multi-step approach that targets the plant’s robust underground structure. Successfully removing this plant depends on understanding its biology and committing to thorough removal methods.
Understanding the Plant’s Persistent Growth Habit
Monkey grass is a member of the lily family, not a true grass. Its resilience stems from a dense, fibrous root system and underground stems called rhizomes. While some varieties, like Liriope muscari, form tight clumps, the invasive Liriope spicata spreads aggressively via these rhizomes.
Rhizomes allow the plant to colonize large areas and store energy reserves. If even a small fragment of a rhizome or root tuber is left, the plant can sprout new growth. This makes simple hand-pulling ineffective, as the roots easily snap off and leave regenerative material behind.
Manual and Non-Chemical Removal Methods
Manual removal is the most precise method for smaller infestations or areas near desirable plants. The process requires thorough digging to ensure the removal of the entire root mat and all associated rhizomes. Perform this task when the soil is moist, which makes digging easier and reduces the likelihood of root fragments snapping off prematurely.
Use a sharp shovel or soil knife to dig up the entire clump, extending several inches beyond the visible foliage and six to eight inches deep. Carefully sift the excavated soil to remove small, round root tubers, which resemble tiny potatoes and store energy. All plant material, including the rhizomes and roots, must be disposed of off-site, as composting can lead to regrowth.
Non-chemical methods can eliminate larger patches by suffocating the remaining plant material. Solarization involves covering the affected area with clear plastic sheeting, which traps solar heat and cooks the remaining roots. Alternatively, smothering the area with thick layers of overlapping cardboard, topped with a six-inch layer of mulch, blocks sunlight and starves the plant.
Effective Chemical Control Strategies
For large, established infestations, systemic herbicides are the most practical solution for long-term control. Products containing glyphosate are absorbed by the leaves and transported through the plant’s vascular system down to the rhizomes and root tubers. This action kills the entire organism, including the persistent underground structures.
Application is most effective when the monkey grass is actively growing, typically during spring or early summer, as the plant efficiently moves nutrients to the roots. Apply the herbicide precisely, painting it onto the foliage or using a shielded sprayer to prevent drift onto surrounding desirable plants, since glyphosate is non-selective.
Multiple applications are necessary to achieve complete eradication due to the plant’s robust energy reserves. A follow-up treatment is required four to six weeks after the initial application to address new sprouts emerging from surviving root fragments. The concentration and application rate should strictly follow the manufacturer’s instructions to ensure maximum efficacy and safety.
Preventing Recurrence and Long-Term Management
After initial removal, vigilance is required to prevent the return of monkey grass from surviving root material. Monitor the treated area closely for the next growing season. Any emerging green shoots should be promptly removed or spot-treated with a systemic herbicide, preventing them from establishing new energy reserves underground.
To prevent re-encroachment, install a physical root barrier made of plastic or metal edging. The barrier should be buried at least 12 to 18 inches deep to block spreading rhizomes. The top edge must extend slightly above the soil line to prevent rhizomes from growing over it. Once the area is clear, amend the soil with compost and choose clumping plants rather than species that spread via rhizomes.