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By Candice Fisher

March 8 2023

5 Minute(s) read

A Step-By-Step Guide on How to Kill Grass Invading Your Garden Bed

Grass intruding into your garden beds certainly doesn’t make for a neat-looking garden, so we’ve come up with some sound advice to avoid this in your garden.

Essentially, solving this common problem comes down to first killing off any lawn that have intruded into your garden beds and then creating a physical barrier to stop them from getting back in. As you do this, it’s important to bear in mind the design of your garden and the type of lawn you have. You’ll also need to commit to some simple regular maintenance.

Depending on your lawn type and the other plants in your garden bed, fighting off grass can be simple or complex. Just ask anyone who has had couch grass invade their garden beds – they will tell you all about the blisters that go along with continually pulling it out! Totally eradicating grass from your garden beds can be done, but it takes a methodical approach.

Let’s look at the process in a bit more detail.


Step 1 – Remove Surface Vegetation

First, remove as much vegetation as possible by hand. If it’s a cool-season grass-type weed, like ryegrass or fescue, it won’t have any runners so that you can pull the grass up, roots and all, and it won’t grow back.

Warm-season grasses, on the other hand – Couch, Kikuyu, Zoysia, and Buffalo – have an underground rhizome (“runner”) system that makes pulling them up more difficult (and is the reason why they’re so good at invading the garden in the first place!). This rhizome system can even tunnel under edging and pop up in neighboring beds. For grasses with runner systems, start by manually cutting the grass down to ground height using a garden knife or hand scythe.


Step 2 – Kill off the Underground Runner System

Once you have removed most of the plant, it’s time to address the underground part of the grass. There are a couple of ways to go about this.

One option is to use a non-selective herbicide such as glyphosate (‘Roundup’), being careful not to spray any on plants you want to keep.

Autumn is the ideal time of year to apply herbicides, as the lawn growth has slowed from its peak but is not yet wholly dormant, meaning it will still take up the herbicide through the leaf. Depending on the grass type and the amount, you may need several spray applications. Be vigilant and ready with a spray bottle to quickly knock over any new invasions as they appear.

A more environmentally friendly option is to block light to the area with a covering such as mulch, cardboard, or newspaper. This can help smother grass growth, though you’ll likely still need to spray a few new shoots as they appear.

Once you’ve achieved good control of lawn invasions, you’re ready for the next challenge – keeping it from re-entering!  


Step 3 – Block the Lawn From Invading the Garden Bed

Establishing a border (“edging”) is the easiest way to keep your lawn from creeping into your garden beds. Hard borders can be made from virtually anything, from store-bought brands of plastic or metal edging that push part-way into the ground through to natural rocks. Whatever material you use, make sure the barrier is sunk deep enough to prevent grass from invading beneath the surface.

Another physical border option is the spade edge, or “English border”. It is basically a shallow ditch dug between the lawn and flower bed. It is quite easy to dig out and maintain and makes it easy to spot weeds and grass runners so that they can be either trimmed or sprayed immediately.

Your choice of edging will depend on many factors, particularly aesthetics and budget. Ideally, you should aim for edging that allows you to easily use a lawn-edger or whipper-snipper along the margin. This way, you can easily tend to your lawn edges at the same time as mowing for a neat, clean finish you can be proud of.

3 Practical Tips For Killing Off Lawn in a Garden Bed

Use a Weed Barrier

Before planting in the garden bed, it's important to lay down a weed barrier to prevent the regrowth of the lawn. A weed barrier can be made of materials such as landscape fabric or thick layers of newspaper. This will help block sunlight and prevent the growth of any remaining grass.

Cut and Spray

Cutting the grass as short as possible and then spraying the area with a non-selective herbicide like glyphosate can effectively kill off the lawn. However, it's important to use caution when using herbicides and follow the instructions carefully to avoid damaging surrounding plants or harming the environment.


This method involves covering the garden bed with a clear plastic sheet and leaving it in place for several weeks during the hottest part of the summer. The heat generated under the plastic will kill off any grass or weeds, making it easier to prepare the bed for planting. It's important to note that this method may also kill beneficial microorganisms in the soil, so it should be used judiciously.


Garden Bed Edging Ideas to Stop Lawn Growth

  • Stone Edging: Using natural stones as garden bed edging can create an attractive and durable barrier to prevent grass from growing into the bed. Depending on the desired look, stones can be placed in various configurations, such as stacked or staggered.
  • Recycled Plastic Borders: Recycled plastic borders are a low-cost and eco-friendly option for garden bed edging. They are easy to install, come in various sizes and colours, and can be cut to fit any bed shape. These borders will not rot or rust and can last for many years.
  • Gabion Walls: Gabion walls are made of wire mesh baskets filled with stones or other natural materials. They are a stylish and functional option for garden bed edging, as they provide a sturdy barrier to prevent grass from growing into the bed while adding texture and visual interest to the garden. Gabion walls can be designed in various shapes and sizes, making them versatile for any garden design.


Get Your Garden Beds Back to Their Best

Stick with these tips and you’ll be able to keep pesky grasses and lawn weeds out of your garden and flower beds for good!