Does mulch kill grass? Technically, mulch prevents light and oxygen from reaching the grass, dying on its own. We have been using mulch to kill unwanted grass and weeds from our lawn for over a decade.

Comprehensive Guide of Using Mulch on Grass

This article includes all the practical pointers we have collected over time on how best to utilize mulch to remove grass from where it does not belong.

Does Mulch Kill Grass?

Yes, a layer of mulch that is adequately thick will kill grass if kept on top of it for an extended period. Mulch has been used to kill invasive grasses and weeds in turfs and lawns for a long time. The type of mulch you choose and the specie of grass to be eliminated are also important factors to consider.

– How Does Mulch Destroy Grass?

Mulch will kill your grass by the simplest means possible: by suffocating it. It will not allow enough sunlight to reach grass blades, and they will be unable to carry out photosynthesis and make food for themselves.

If the mulch layer is thick enough and made of more waterproof material, it will also block the air supply to the plants. This helps the grass die even faster as it cannot carry out any gaseous exchange.

Unlike chemical methods of killing grass, you should give mulch a lot of time to perform its suffocation. 

– Choose Your Mulch Wisely

The most common type of mulch that we find is bark mulch. It makes a decent cover and can kill all except the most invasive types of stolon-growing grasses. It is available almost everywhere and is quite long-lasting. The only downside is that it is light and blows away in strong winds and rain.

Paper mulch is a good option because you can use as many newspapers as possible to make a thick layer. Wetting the newspaper layers slightly will help them stick to each other and give cohesiveness to the mulch. We like to use paper mulch as a base material with all other types of mulch.

Choosing Mulch Wisely for Grass

Plastic mulch suffers from one major disadvantage: its inability to decompose organically. However, if you search for it, you might also find degradable types of plastic mulch. This mulch works perfectly to smother grass from any light or oxygen. You can then top it off with the organic mulch of your liking.

Rock mulch or gravel is another personal favorite option. It will kill not only grass but most weeds as well. Some stolon-based grasses will try to grow through cracks in the gravel, and you can stop that by adding a layer of another type of mulch.

– Cut Down Grass First

Demarcate the area where you want to remove the grass by mulching. You need to mow the grass in this area down to the very base of the soil using a lawn mower

If the grass is already shorter than three inches, you can leave it as such. Otherwise, set your lawn mower at the lowest possible setting.

Cutting Grass on the Lawn

The grass needs to be as short as possible so that the overlying newspaper and mulch will lay evenly and flat over it.

See if any perennial weeds are growing along with the grass in that area. These are very tough species that will die with the grass under the mulch but then return after a while. It is better to uproot these weeds by hand or using a rake.

– Spread Cardboard Or Newspaper Over Grass

Next, you must decide whether you want to lay newspaper or cardboard over the grass first. When choosing a newspaper, it needs to be at least ten layers thick. 

The cardboard layer needs to be thick enough as well. Please ensure all pieces of cardboard and newspaper are overlapped at the edges so that no light or air can escape through them.

Water this layer with a little water to make it more compact and for newspapers and cardboard to stick together. Don’t water too much, or they will become soggy, defeating the whole purpose.

– Lay Mulch Over The Cardboard

Once your newspaper and cardboard layer is established, it is time to cover it with mulch. The perfect thickness of mulch is six inches or more and four inches at the minimum. Mulch thinner than four inches will not be able to block out light properly.

While laying mulch, take care not to disturb the cardboard or newspaper base you had established. Mulch will also need to be watered to compact and adhere to the base. 

Mulch Over the Cardboard

You must give mulch for at least three months to kill the grass completely. During this time, the mulch and the cardboard layer will break down. There will be no more reason to water mulch anymore.

If you live in a windy region, you must put something weighted on top of the whole ensemble to keep it from blowing over. 


– Preventing Grass From Growing Through Mulch

Putting mulch over a base of newspaper or cardboard will prevent grass from growing and kill it over time. However, some stubborn and invasive varieties, such as bermudagrass, might persist and regrow again when the mulch is removed.

This is when you need to go for a landscaping fabric instead of a cardboard piece. Put the fabric over the area of grass that you have chosen and hold it down using pins or nails. Again, place a thick layer of an appropriate type of mulch to cover it. You can obtain reasonably priced landscaping fabric from any local hardware store.

You can combine mulching with chemical means to increase the efficacy of your grass-killing action. Either sprinkle vinegar mixed in water with a dash of dishwashing soap to help kill grass before adding mulch. Concentrating salt water will also desiccate grass and add dehydration and suffocation.

– Organic vs Inorganic Mulch

Organic mulch includes wood chips, compost, bark, pine needles, and paper. Ironically some of these things, such as compost, are also used to make grass grow. The good thing about this mulch is that it breaks up eventually and gets added to the soil in one useful form.

Using Organic Mulch on Grass

As for inorganic mulch, its prime examples include sheet mulching and landscape fabric. Instead of making grass grow, they kill it by cutting off its light. Some of them, like black plastic, also produce a large amount of heat that aids in getting rid of the grass. 

Unless you use special degradable types of inorganic plastics, this latter type of mulch will not break down on its own. You will have to collect and discard it after the grass underneath has been killed.

Frequently Asked Questions

– Does Grass Grow Through Mulch?

Grass can grow through mulch when it is not layered properly. Some grass species are particularly resistant to mulching. These primarily include those that spread through above-ground stolons. They will stay alive even if there are minor gaps in your mulch layer and continue to grow through those gaps.

– Will Mulch Kill Weeds Underneath?

Mulching will kill most weeds that are placed underneath it. However, this is never a permanent solution. Only the upper grassy parts of the weeds die while the roots remain unaffected. Once mulching is removed or compromised, the weeds will grow back.


Today you learned how to utilize mulch to get rid of grass wherever you don’t want it.

Here are some key points about grass-killing mulching you need reminding of.

  • You must create a very thick and nearly impenetrable layer of mulch to kill any grass underneath it.
  • It is best to place a layer of newspaper or cardboard and then layer another mulching material over it.
  • It will take a long time for mulch to kill weeds and grass properly. You might have to wait as much as three months or even more in some cases.
  • Mulching will kill most weeds that are placed underneath it. However, this is never a permanent solution.

We hope that the next time you have to use a mulch to kill any patch of grass you will know exactly what to do. Information from this article will come to your aid in your endeavours.

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