How to Compost Grass Clippings (Add This To Keep It Dry)

Many gardeners end up with leftover grass clippings each week after moving the lawn.  Some even find extra grass clippings from family, friends, or local landscaping companies.  Although grass clippings can be used as a type of mulch, it can also be used as one ingredient in compost.

So, how do you compost grass clippings?  To compost grass clippings, be sure to add plenty of carbon-rich material (browns), such as fallen leaves, to your compost pile.  Keep the pile wet enough, and turn the pile often to help aerate the compost.  This will encourage bacteria to decompose the pile.

 Of course, you should always remember to wear a mask when working with grass clippings, especially if you are allergic.  Also, avoid using grass clippings from lawns that are treated with pesticides or herbicides.

Let’s take a closer look at how to compost grass clippings.  Then, we’ll answer some common questions about using grass clippings in the garden.

(You can also check out my YouTube video on how to make compost if you like!)

How to Compost Grass Clippings

The first step in composting grass clippings is to make sure that your source of grass clippings is safe.  Do not use grass clippings that come from lawns treated with pesticides or herbicides.

Avoid grass clippings that come from lawns treated with herbicides or pesticides to keep chemicals out of your compost and garden.

There are several ways to find grass clippings you can use for your compost pile:

  • Grass clippings from your own lawn
  • Grass clippings from neighbors, friends, and family
  • Grass clippings from local landscaping companies
  • Grass clippings from a municipal compost site

Once you have a safe supply of clean grass clippings, it is time to start your compost pile.  The next step is to find some “browns” to add to your pile.

Grass clippings contain lots of nitrogen, which makes it a “green” (nitrogen-rich) compost material.  Sawdust, on the other hand, contains lots of carbon, which makes it a “brown” (carbon-rich) compost material.

You want a good mix of brown and green materials in your compost pile, so that the carbon and nitrogen levels are balanced.  For example, too much carbon will tie up all of the available nitrogen in the pile, and if there is not enough, the pile will decompose slowly (if at all).

Some common carbon-rich brown materials that you can add to the grass clippings in your compost pile include:

  • Brown (fallen) leaves
  • Pine needles
  • Mulch or wood chips
  • Twigs and thin branches
  • Tree bark
  • Sawdust
  • Wood ash
  • Cardboard
  • Paper
  • Straw
  • Corn stalks
Sawdust is one “brown” (carbon-rich) composting material. Don’t use too much, since it contains a lot of carbon and can quickly dry out your compost pile.

For more information, check out some of my articles on composting:

Remember that grass clippings usually contain lots of water, so too much can leave you with a compost pile that is too wet.  To counter this, you can add sawdust, which is very dry and can help to absorb some of the water in the grass.

Just be careful not to add too much sawdust, since it is incredibly carbon-rich.  For more information, check out my article on composting sawdust.

How Long Does It Take To Compost Grass Clippings?

According to the University of Illinois Extension, grass clippings can be composted within 3 months.  This assumes a few things, though:

  • you have the proper ratio of carbon to nitrogen in the compost pile (browns, like leaves or sawdust, to go along with the greens, like grass clippings)
  • you maintain the proper moisture level in the compost pile (not too wet, not too dry)
  • you turn the compost pile to aerate it (to encourage bacterial growth and activity)
Grass can take anywhere from 3 months to a year to compost completely, depending on what else you put in the pile and the care you give.

Of course, this means that pure grass clippings by themselves will decompose much more slowly, perhaps a year or longer, especially if left unattended.

For more information, check out this article on compost from the Iowa State University Extension.

To give grass clippings a quick carbon boost, add a little sawdust (this will also dry out the pile a bit if it is too wet).

For more information, check out this article from the University of Missouri Extension, which has a table with carbon to nitrogen ratios for sawdust and other compost materials.

How to Compost Grass Clippings Faster

You may not want to wait a year or more for your grass clippings to turn into compost that is ready for the garden.  Luckily, there are a few steps you can take to speed up the composting process for grass clippings.  Let’s get into those now.

Add Finished Compost, Animal Manure, or Topsoil to Your Compost Pile

Many times, a compost pile has the proper air and moisture levels, and it has the correct ratio of green to brown materials.  It just needs a little “boost” to get it started on the path to decomposition.

One great way to give your compost pile the boost it needs is to add materials that already contain plenty of the bacteria that you want.  A few things that already contain bacteria that help to break down compost include:

  • Finished compost – this is compost that has completely decomposed.  It looks and smells like fresh earth, and there is no detectable trace of the materials that were originally part of the pile.
  • Animal manure – this includes waste from animals (such as chickens, cows, horses, etc.) and also their bedding (sawdust, wood shavings, straw, and hay).  In addition to containing bacteria, animal waste contains plenty of nitrogen (you can tell by the smell!)
  • Topsoil – healthy topsoil from your garden should contain bacteria that will help to break down the materials in a compost pile.  If you are lucky, your topsoil may also contain some worms, which can help to break down a compost pile even faster.
Adding manure to your compost pile can help to give it the bacterial boost it needs to speed up the decomposition process.

Keep Your Compost Pile Moist (But Not Wet!)

In order for the bacteria in a compost pile to do their work of decomposing the materials in the pile, they need the proper moisture levels.  It should not be too wet, and it should not be too dry.

Unfortunately, grass clippings are usually very wet, and adding a lot of them to your pile can absorb leave the compost too wet.  This will prevent the bacteria in the pile from doing their work.

Generally, you can tell that the bacteria are not working if the pile is cool or warm, rather than hot.  A compost pile can get up to 140 degrees Fahrenheit when the bacteria are really working!

Don’t worry if the compost pile gets too wet after a heavy rain, or if you added too much water by mistake.  In that case, simply add some sawdust to absorb the extra water.

A little sawdust can soak up a lot of water in your compost pile, and will add carbon if your pile is heavy on green (nitrogen-rich) materials.

Just make sure to add enough extra green compost materials (like grass clippings) to offset the extra sawdust you added (remember, it’s all about balancing the carbon and nitrogen in the pile!)

Aerate Your Compost Pile By Turning It

In addition to moisture, the bacteria in your compost pile need air (oxygen) in order to work properly.  If your pile just sits there, it may not get the air circulation it needs.

One way to aerate your compost pile is to simply turn it over with a shovel or pitchfork.  When you do this, you should see steam coming up from the hot compost if the bacteria are working properly.

Use a shovel or pitchfork to turn your compost pile regularly. This will provide aeration and give bacteria the oxygen they need to do the work of decomposition.

You should turn your compost pile anywhere from 1 to 2 times per week to give it the proper aeration.

Another option is to use a compost tumbler to store your pile.  This will allow you to protect the pile from getting too much rain.

More importantly, it will allow you to turn the tumbler by hand without using a shovel or pitchfork.  The best part of all is that you can put a wheelbarrow right under the tumbler and empty the compost for easy transport when it is fully decomposed.

For more information, check out this article on home composting from the Penn State University Extension.

Can You Put Grass Clippings In The Garden?

Yes, grass clippings can be used in the garden as mulch.  A layer of grass clippings as mulch can insulate the soil against temperature changes and help to retain moisture in the soil on hot, dry days.

However, you should not use grass clippings as compost in your garden.  Avoid mixing uncomposted grass clippings into your soil as you would with compost.

Without a rich source of carbon, the grass clippings may take a long time to decompose and release their nutrients into the soil.  You are better off composting the grass clippings in a separate pile with other browns, as mentioned above.

Will Grass Clippings Kill Weeds?

Yes, grass clippings will kill weeds.  A thick enough layer of grass clippings will smother any existing weeds by denying them air and sunlight, or by making it too hot for them to survive.

Grass clippings can be used to smother existing weeds to to prevent weeds from growing in the future.

A layer of grass clippings will also help to prevent seeds of weeds from taking root later in the growing season.


Now you have a much better idea of how to compost grass clippings, which can save you money on fertilizer for your garden.  You also know about its other uses, and how not to use it in the garden.

I hope you found this article helpful – if so, please share it with someone who can use the information.

You can learn how to use compost in your garden here.

This article can help you to decide whether to use a container for compost or not.

No-dig gardening is a great way to improve soil health that focuses on compost – you can learn more here.

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Jon M

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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