Killing Monkey Grass – Reclaiming Your Landscape From Invasive

ByRimon Chowdhury Updated on

Do you feel like your garden is being slowly overtaken by those stubborn green clumps that just won’t stay in their lane? I know exactly how frustrating it is to watch a once-orderly border turn into a chaotic mess of sprawling foliage.

The good news is that killing monkey grass doesn’t have to be a lifelong battle if you use the right strategies to target the root system. In this guide, I will show you how to eliminate these plants once and for all while keeping your other flowers safe.

We will cover everything from the “dig and sift” method to organic smothering and targeted chemical applications so you can reclaim your beautiful outdoor space today. Don’t worry—getting your garden back is easier than you think with a little patience!

Understanding Your Opponent: Liriope vs. Mondo Grass

Before we start the removal process, we need to know exactly what we are dealing with in your yard. Most gardeners use the term “monkey grass” to describe two different plants: Liriope and Ophiopogon (Mondo grass).

While they look similar, their growth habits dictate how difficult the removal process will be for you. Clumping varieties, like Liriope muscari, stay in neat mounds and are generally much easier to manage or relocate.

The real trouble comes from Liriope spicata, often called creeping lilyturf, which spreads via aggressive underground rhizomes. This variety is the one that usually requires a more intensive approach to ensure it doesn’t pop back up next spring.

The Role of Fleshy Tubers

Monkey grass survives and thrives because of its unique root structure, which includes small, fleshy tubers that store water and nutrients. These tubers act like a “battery pack” for the plant, allowing it to survive drought and neglect.

If you leave even a few of these tubers in the soil during the removal process, the plant can regenerate. This is why simply pulling the leaves off never works—you have to address the energy source hidden beneath the surface.

Why Spreading Varieties Are Invasive

In many regions, creeping monkey grass is considered an invasive species because it displaces native plants and chokes out delicate perennials. Its dense root mat is so thick that even weeds struggle to grow through it.

Recognizing that you are fighting a plant designed for survival will help you stay patient. It’s not your fault the plant is stubborn; it’s just doing what nature designed it to do very effectively.

The Physical Removal Strategy: The Dig and Sift Method

For small patches or areas where you want to plant something else immediately, manual removal is the most reliable method. I always recommend doing this after a heavy rain when the soil is soft and pliable.

You will need a sturdy garden fork rather than a traditional shovel, as a fork is less likely to slice the rhizomes into pieces. Slicing the roots can actually lead to more plants, as each segment can potentially grow into a new clump.

Start by loosening the soil about six inches away from the edge of the visible leaves to ensure you catch the outward-reaching roots. Lift the entire clump upward, shaking off as much excess dirt as possible back into the hole.

Sifting the Soil for Success

Once the main clump is out, your work isn’t quite finished yet. You must go through the loosened soil with a hand rake or your fingers to find any remaining white tubers or root fragments.

I like to think of this as a treasure hunt, though the “treasure” is something we definitely don’t want to keep! Even a piece the size of a fingernail can lead to a new sprout in a few months.

Discard the pulled plants in your heavy-duty trash bags rather than your compost pile. Most home compost bins do not get hot enough to kill the resilient seeds and roots of this particular species.

Tools for the Job

  • Garden Fork: For lifting soil without cutting the root system.
  • Hand Trowel: For precision work around the roots of nearby desirable plants.
  • Sifting Screen: If you have a large area, a simple mesh screen can help separate tubers from the soil.

Smothering and Solarization: The No-Dig Approach

If you have a large area covered in monkey grass and you aren’t in a rush, smothering is a fantastic organic option. This method uses a physical barrier to block sunlight and “starve” the plants over several months.

I highly recommend using corrugated cardboard for this process because it is biodegradable and thick enough to prevent shoots from poking through. Avoid using thin newspaper, as monkey grass can often pierce right through it.

Lay the cardboard over the area, overlapping the edges by at least six inches so no light can reach the soil. Wet the cardboard down thoroughly to help it settle and begin the decomposition process.

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Using Solar Heat to Your Advantage

Another variation of this is solarization, which involves covering the area with clear plastic sheeting during the hottest months of the summer. The plastic traps heat, essentially “cooking” the roots and seeds in the top few inches of soil.

For solarization to work, the plastic must be airtight and left in place for at least 6 to 8 weeks of intense sun. This is a great choice for southern climates where summer temperatures regularly soar.

While this method leaves the area looking a bit unsightly for a season, it is incredibly effective at killing the root bank without the use of harsh chemicals. Your future self will thank you for the lack of weeding!

The “Lasagna” Layering Technique

  1. Mow the monkey grass as short as possible to weaken the foliage.
  2. Cover the area with thick cardboard (remove any plastic tape first).
  3. Add a 4-inch layer of hardwood mulch or wood chips on top of the cardboard.
  4. Wait 6 to 12 months for the plants underneath to completely decompose.

Effective Methods for killing monkey grass

Sometimes, the sheer volume of the invasion or the physical difficulty of digging makes manual removal impossible. In these cases, killing monkey grass with a systemic herbicide is often the most practical path forward.

Systemic herbicides work by traveling from the leaves down into the root system and those pesky tubers. Because monkey grass has a waxy coating on its leaves, you must use a product specifically designed to penetrate tough foliage.

I suggest looking for a product containing glyphosate or triclopyr. These are non-selective, meaning they will kill almost any green plant they touch, so you must be extremely careful with your application.

Improving Herbicide Absorption

One “pro tip” I always share with my friends is to mow the monkey grass a few days before spraying. The fresh cuts on the leaf blades allow the herbicide to enter the plant’s vascular system much more quickly and effectively.

You can also add a surfactant or a few drops of dish soap to your sprayer mix. This helps the liquid “stick” to the vertical, waxy leaves instead of just rolling off onto the ground where it won’t do any good.

Apply the treatment on a calm day with no wind to prevent “drift” onto your prized roses or hydrangeas. If the monkey grass is growing right next to a plant you love, use a piece of cardboard as a shield while you spray.

Safety and Environmental Precautions

Always wear long sleeves, gloves, and eye protection when handling garden chemicals. It is also vital to keep pets and children away from the treated area until the spray has completely dried.

Check your local weather forecast to ensure no rain is expected for at least 24 to 48 hours. Rain can wash the chemicals into storm drains or nearby water sources, which we definitely want to avoid.

Remember that one application might not be enough. Spreading varieties of Liriope are incredibly resilient, and you may need to perform a follow-up spot treatment three weeks later to catch any “escapees.”

Natural and Household Alternatives

If you prefer to avoid synthetic chemicals, there are a few household items that can assist in the battle. While these methods require more frequent application, they are safer for the overall soil health and local pollinators.

Horticultural vinegar (which has a much higher acidity than the stuff in your kitchen) can burn the foliage of monkey grass effectively. It works best on a hot, sunny day when the sun can help desiccate the leaves.

Keep in mind that vinegar is a contact killer, not a systemic one. This means it will kill the green leaves but likely won’t reach the tubers. You will need to re-apply every time you see new green shoots until the roots finally run out of energy.

The Boiling Water Trick

For very small patches or cracks in a sidewalk, boiling water can be a surprisingly effective tool. Carefully pouring a kettle of boiling water over the crown of the plant can damage the cells and kill the immediate growth.

This is a great option for those who want a zero-chemical approach, but it is physically demanding to carry hot water back and forth. It is also most effective on younger plants rather than established, decades-old colonies.

Regardless of the natural method you choose, consistency is the key. You are essentially trying to starve the plant of its ability to photosynthesize, so you must be diligent about killing monkey grass sprouts as soon as they appear.

Using Salt (With Caution!)

Some people suggest using salt, but I strongly advise against this in most garden settings. Salt can linger in the soil for years, making it impossible for any plants to grow in that spot in the future.

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Only use salt if you are treating a gravel driveway or a permanent path where you never intend to plant anything again. For flower beds, stick to vinegar, heat, or manual removal to preserve your soil’s fertility.

Preventing a Monkey Grass Re-Invasion

Once you have successfully cleared the area, the last thing you want is for the monkey grass to come creeping back from a neighbor’s yard or a missed root fragment. Prevention is your best defense!

Installing a root barrier is a highly effective way to stop spreading varieties in their tracks. Use a heavy-duty plastic or metal edging that extends at least 8 to 10 inches deep into the soil.

Most rhizomes travel in the top few inches of soil, so a deep barrier acts like an underground wall. Make sure the barrier sticks up about an inch above the soil line to prevent the “runners” from simply hopping over the top.

Replacing with Better Alternatives

Nature hates a vacuum! If you leave the soil bare after removing the liriope, weeds or remaining monkey grass bits will quickly fill the space. I recommend planting a non-invasive groundcover as soon as possible.

Consider native alternatives like wild ginger, creeping phlox, or sedum. These provide the same low-maintenance “green” look without the aggressive spreading habits that caused your headache in the first place.

Mulching the area heavily with 3 inches of organic matter will also help suppress any tiny sprouts that try to emerge. Plus, it makes your garden look finished and professional while the new plants get established.

Ongoing Monitoring

Make it a habit to walk through your garden once a week during the growing season. If you see a single blade of monkey grass emerging, pull it immediately while the root system is still weak.

Early intervention is the difference between a five-minute task and a weekend-long project. Staying vigilant ensures that your hard work in killing monkey grass pays off for years to come.

Frequently Asked Questions About killing monkey grass

Can I kill monkey grass with a weed whacker?

No, using a weed whacker will only remove the top foliage. Since monkey grass grows from underground rhizomes and tubers, it will simply grow back from the roots within a few weeks, often coming back thicker than before.

How long does it take for cardboard smothering to work?

In most cases, it takes a full growing season (about 6 to 12 months) for the cardboard to completely kill the root system. It is a slow process, but it is very effective for large-scale removals without using chemicals.

Is monkey grass toxic to pets?

Liriope is generally considered non-toxic to dogs and cats, though eating large amounts can cause mild stomach upset. However, if you have used chemical herbicides for killing monkey grass, you must keep pets away until the area is dry and safe.

What is the best time of year to remove monkey grass?

Early spring is often the best time because the ground is moist and the plant is just starting its growth cycle. However, if you are using herbicides, late summer or early fall is effective because the plant is busy moving nutrients down to its roots for winter.

Conclusion: Your Path to a Liriope-Free Garden

Removing unwanted monkey grass can feel like an uphill battle, but you now have the tools and knowledge to win the war. Whether you choose the physical labor of digging, the patience of smothering, or the efficiency of targeted sprays, the key is persistence.

Remember that even the most experienced gardeners face these challenges. Don’t be discouraged if a few sprouts reappear; just stay on top of them, and eventually, the root system will give up. Your garden is a reflection of your care, and reclaiming it from invasive spreaders is a huge win!

So, grab your garden fork or your favorite mulch, and get started this weekend. You are just a few steps away from the beautiful, organized garden you’ve always wanted. Go forth and grow!

Rimon Chowdhury
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