Monkey grass, including species like Liriope and Ophiopogon, is often chosen for its durability as a groundcover. The challenge in removing it stems from its robust, underground growth structure, especially the aggressive variety, Liriope spicata, which spreads via rhizomes. These horizontal stems produce new shoots and roots, allowing the plant to rapidly colonize an area. A natural approach relies on intensive manual labor and passive, long-term environmental controls to eliminate this resilient plant without synthetic herbicides.
Immediate Physical Removal Techniques
The most direct way to eliminate monkey grass is through manual excavation, which demands meticulous attention to detail. This method is best suited for smaller patches where the rhizome network can be physically contained. Begin by using a sharp spade or trowel to cut deeply around the perimeter of the patch.
Work to lift the entire plant clump, including the root ball, digging at least 8 to 12 inches deep to reach the majority of the rhizomes. A garden fork is an effective tool to loosen the dense soil and lift the root mass without chopping the rhizomes into smaller pieces. Even tiny fragments of rhizomes left behind can resprout, initiating new growth.
After removing the bulk of the plants, sift the excavated soil to capture any remaining root fragments. Spreading the soil over a fine mesh screen or a tarp allows you to visually inspect and physically remove small root sections. This thorough sifting process prevents immediate recurrence, as stored energy in the root pieces can fuel new growth.
Long-Term Smothering and Solarization
For larger, established areas where manual digging is impractical, passive techniques like smothering and solarization offer effective, non-labor-intensive alternatives.
Smothering
Smothering works by completely blocking sunlight, which starves the plant of the energy needed for photosynthesis. Achieve this by laying down thick, opaque materials such as overlapping layers of cardboard or a heavy-duty black plastic tarp directly over the monkey grass.
The smothering material should extend at least two to three feet beyond the edge of the patch to prevent rhizomes from growing around the barrier. Cover the material with a thick layer of mulch, compost, or soil to hold it in place and block any light leaks. This method is slow, often requiring the material to remain in place for six to twelve months to fully deplete the rhizomes’ energy reserves.
Solarization
Solarization utilizes clear plastic sheeting to trap solar radiation, raising the temperature of the top six to twelve inches of soil to levels lethal to the roots and seeds. This process is most effective when performed during the hottest months of the year. After clearing the area of debris, water the soil thoroughly and cover it with a clear, UV-resistant plastic tarp.
The edges of the plastic must be completely sealed by burying them in a shallow trench of soil to trap the heat and moisture. Soil temperatures under the plastic can exceed 120 degrees Fahrenheit, essentially “cooking” the monkey grass roots. This method typically requires four to eight weeks of consistent, intense sun exposure to be successful.
Preventing Recurrence and Containment
Following the removal of existing monkey grass, proactive measures are necessary to prevent its return. The most reliable containment strategy is installing a physical root barrier to block the spread of aggressive rhizomes. This barrier must be made of a durable, impermeable material, such as high-density polyethylene (HDPE) or metal flashing.
The barrier should be placed vertically into the ground to a depth of at least 18 to 24 inches to intercept the traveling rhizomes. It must also extend two to three inches above the soil line to prevent stems from creeping over the top. This creates a complete underground and above-ground seal against the plant’s lateral spread.
Ongoing monitoring is essential in the years following removal to catch any isolated regrowth. Inspect the area regularly for grass-like shoots, particularly near the containment barrier or where root fragments may have been missed. Immediately dig out any new shoots by hand, removing the entire small root mass before it can re-establish itself.
Consider replacing the monkey grass with less aggressive groundcover alternatives that do not spread by invasive rhizomes. Clumping sedges (Carex species) or non-running varieties of Liriope muscari are good choices. Selecting a non-running groundcover helps maintain control over the garden space, eliminating the need for future intensive removal efforts.