How To Kill Monkey Grass: A Comprehensive Guide To Permanent Eradication

Eradicating monkey grass (Liriope muscari and Ophiopogon japonicus) requires a combination of aggressive physical excavation and systemic chemical intervention, as the plant’s dense tuberous root system allows it to regenerate from fragments as small as one inch. Achieving complete removal typically involves a multi-season approach of monitoring for regrowth and applying non-selective herbicides to remaining subterranean rhizomes.

Strategic Preparation and Site Assessment Requirements

Successfully removing monkey grass is rarely a one-time event due to its high resilience and survival strategy. Before beginning, evaluate the density of the infestation and the surrounding vegetation. If the monkey grass is encroaching on ornamental plants you intend to keep, you must prioritize mechanical isolation before applying chemical agents.

• Essential Equipment: Sharp spade or garden mattock for deep excavation, heavy-duty landscaping rake, lawn mower or string trimmer, non-selective herbicide containing glyphosate or imazapyr, pressurized pump sprayer, and thick nitrile gloves.
• Mandatory Prerequisites: Conduct the primary removal during the plant's active growing season (late spring to early summer) when the plant is translocating carbohydrates to the foliage. This maximizes the uptake of herbicides.
• Safety and Standards: Always utilize personal protective equipment (PPE) when handling herbicides. Adhere to all label instructions regarding application rates, as excessive chemical use can cause soil sterilization, preventing the growth of desired flora for months.
• Duration Benchmarks: For a standard 100-square-foot patch, budget 4 to 6 hours for initial mechanical removal. Follow-up monitoring should occur every 21 days for the remainder of the growing season.

Systematic Eradication Workflow

Step 1: Mowing and Initial Stress Induction

Before digging, mow the monkey grass down to the soil surface using a string trimmer. This removes the foliage canopy, exposing the soil level and making it easier to identify the crown structures. Clearing the top growth also forces the plant to tap into its root reserves for energy, making it more vulnerable to subsequent herbicide application or mechanical removal.

Step 2: Mechanical Excavation of Root Mats

Using a sharp spade or mattock, sever the ground around the perimeter of the infestation. Dig to a minimum depth of 8 to 10 inches. Monkey grass possesses a dense network of thick, fleshy roots and rhizomes that store significant energy. Use a pitchfork to pry the root mass upward, being careful to shake the soil loose and sift through it to capture any broken fragments.

Warning: Do not place removed monkey grass in a standard compost pile. The high moisture content of the tubers can lead to the plant re-rooting in the pile. Bag all material in thick contractor-grade plastic bags for landfill disposal.

Step 3: Targeted Systemic Herbicide Application

Once the bulk of the vegetation is removed, wait approximately 7 to 14 days. During this period, any remaining root fragments will begin to sprout new green foliage. This is the "flush" stage. Once this new growth reaches 2 to 3 inches in height, apply a systemic, non-selective herbicide directly to the leaves. Glyphosate is the standard for home landscapes, as it translocates through the plant tissues down into the rhizomes, killing the organism from the inside out.

Pro-Tip: Use a cardboard shield or a piece of plywood when spraying near desirable plants. This prevents herbicide drift, which can easily damage or kill turfgrass and ornamental shrubs.

Step 4: Maintenance and Re-evaluation

Monitor the site every three weeks. Monkey grass is notorious for its ability to hide dormant buds that may not emerge for several months. If you observe any green blades appearing in the treated area, perform a spot treatment with herbicide immediately. Do not introduce new mulch or topsoil until you have confirmed a period of at least 60 days without any regrowth.

Comparative Analysis of Eradication Methodologies

Field Troubleshooting and Failure Mitigation

• Failure Scenario: Persistent Regrowth in Patches

  
  
  
  • Root Cause: Failure to remove the entire subterranean tuberous system.
  • Actionable Fix: Re-excavate the specific area to a depth of 12 inches to ensure all fleshy rhizomes are extracted. Spot-spray any emerging leaves with a higher-concentration herbicide solution, ensuring the weather is dry and temperatures are between 60 and 85 degrees Fahrenheit.

• Failure Scenario: Herbicide Drift Damaging Ornamentals

  
  
  
  • Root Cause: Applying herbicide on a windy day or failing to use a physical shield.
  • Actionable Fix: Immediately wash off the affected leaves of the non-target plants with a heavy stream of water to dilute the chemical. Prune away heavily scorched foliage to stimulate new, healthy growth.

• Failure Scenario: Stunted Growth of New Plantings

  
  
  
  • Root Cause: Residual soil activity or extreme exhaustion of soil nutrients during the eradication process.
  • Actionable Fix: Amend the soil with high-quality organic compost or aged manure to restore biological activity. Wait at least 30 days after the final herbicide application before introducing any new plants to the site.

Frequently Asked Questions

Can I kill monkey grass with vinegar or natural alternatives?

Natural alternatives like horticultural vinegar (acetic acid) are ineffective against monkey grass. They function only as contact killers, burning the surface foliage without reaching the extensive root system, which will simply produce new shoots within weeks.

Will rototilling get rid of monkey grass?

Rototilling is generally counterproductive. It slices the tuberous roots into small pieces, and because monkey grass can regenerate from root fragments, rototilling effectively propagates the infestation rather than eliminating it.

How long does it take for herbicide to kill the roots?

When using a glyphosate-based herbicide, it typically takes 7 to 14 days to see systemic wilting and yellowing. Total root death may take up to 21 days depending on ambient temperatures and the health of the plant.

Is it necessary to dig up the roots if I use herbicide?

Yes. While herbicides will kill the plant, leaving the dense, tuberous root mass in the ground creates an environment where new weeds will quickly colonize the decaying organic matter. Manual removal provides the cleanest site for future landscaping.

Professional Landscaping Best Practices

Consistent, multi-stage management is the only reliable method for long-term control of monkey grass. Implement these steps with precision to ensure your garden remains free of invasive ground covers and ready for your next design project.