how long does it take for grass clippings to decompose

During the summer months, it can feel like you are drowning in grass clippings.

The lawn grows in the blink of an eye and you are trimming, strimming, and mowing what feels like every other day. What to do with the clippings can be a bit of an issue if you’re bagging them and sending them to landfills where they take up a lot of space and often cause ground pollution.

Really, it’s a waste to send your clippings to the landfill because they contain so many nutrients that can help your lawn and other areas of your garden grow.

There are many ways to use your clippings in the garden from leaving them where they lie to making compost with them. All these processes rely on the clippings decomposing and releasing the nutrients they have stored.

Leaving the clippings on the lawn is known as grasscycling and it is a really effective way to reduce the amount of grass that ends up in landfills.

However, it also has great benefits for your garden and lawn. As the grass decomposes it releases the nitrogen it has stored making it a great fertilizer substitute.

An added benefit is that you no longer need to spend hours raking and bagging your clippings. Just leave them where they lay! 

Sometimes it is not feasible to leave the clippings on the lawn. Perhaps the clippings are very long or it has rained recently.

In these cases, you can use your lawn clippings in your compost bin to create some really rich compost for your garden. 

Another great way to use your lawn clippings is to turn them into mulch for your flowerbeds or vegetable patches. Fine cuttings are easily spread onto the soil and release their nutrients as they decompose. 

All these processes rely on the clippings decomposing and releasing the nutrients they have stored.

So how long does this process take? 

Well, it depends on the method, length, and condition of the clippings. No matter whether you are leaving them on the lawn or composting or mulching, you do not want long clippings.

This is because bigger pieces of organic matter take much longer to decompose. In the case of grass clippings, longer pieces can mat together and create thatch which is dry, dead plant material.

It can become hard and difficult to remove and prevents water and sunlight from reaching anything underneath. 


Grass clippings go flying out of a rotary style lawn mower.

Clippings of around an inch in length are perfect for leaving on the grass. You can achieve this by setting your mower blades to a higher height or by using a mulching mower.

Either way, once you’ve mown the lawn, leave the clippings to settle near the roots. This shouldn’t take more than a day but if you are still seeing the clippings clinging to the leaves of the grass you can rake them into the root area. 

After a few days, the clippings will begin to decompose. This process will vary in length depending on the weather. To decompose grass needs moisture and warmth so in hot, humid areas it will decompose in a few short weeks. In cool, dry areas this could take a bit longer. 

You can help the process along by regularly watering your lawn as normal and making sure larger bits of debris or piles of clippings are picked up or raked out.


Using your clippings for mulch in other areas of your garden works in a similar way to leaving them on the lawn. 

Once you have mown the lawn, collect the clippings, and make sure they are no longer than an inch in length. This can mean having to chop them if they are longer. Don’t skip this step because you’ll end up with thatch on your flower beds which will prevent water and sun from getting to your soil. 

This mulch will decompose in about a week or two providing you only do a thin layer over the soil. Thick layers or clumps will lead to matting as the microbes in the soil won’t be able to reach all of the material. 


Composting, as any gardener will tell you, is a long game. Grass clippings can be used to make rich compost for your garden but you need to get the ratios right.

For the most effective compost, you should mix your clippings with dry materials such as straw or leaves this should be a 50/50 mix. You can mix your compost materials on top of bare soil or in a compost bin with a layer of soil at the bottom. 

You want to make sure that you don’t have thick layers of grass as this can lead to anaerobic decomposition which is the smelly kind. It won’t retain the nutrients that you want for your compost if it is decomposing anaerobically. 

A key step to composting is turning the material over so that you don’t get clumps of material. A good guide is to turn a pile every week and a tumbler every few days. This will help your compost pile breakdown and mix in. 

Composting your clippings will take about four months depending on the mix and the soil you have used. It is not a quick process but definitely a worthy one. 

Some people claim to have grass clippings turned into compost in little over a week by adding a tonic of beer, cola, and ammonia but for your average compost pile, a few months should do the trick. 


Things to Remember:

  • However you plan on using your clippings, make sure they are short to prevent mats from forming.
  • Wet grass clumps and mats much more than dry grass so don’t use wet grass for mulch or grasscycling. 
  • If you have sprayed your grass with herbicides before cutting, you need to wait about 4-6 weeks before you can use it as mulch or compost. This is because the chemicals will be present even after being cut.

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