Is Compost Bad for Grasses? 5 Things To Know

Compost can be a great asset to help with plants, fruits, and vegetables around your garden. Seeing how much it can benefit other parts of your garden, it is no surprise that some people wonder if it can help their grass as well. 

Compost is not bad for your grass. In fact, there are many benefits to adding compost to your struggling grass as long as you do it carefully. Compost is full of nutrients that your lawn needs to thrive, but these nutrients can also help weeds thrive so it’s important to avoid this.

Before you leap straight into using compost on your lawn let me walk you through a few things you need to know.

Things To Know Before Using Compost on Grass

Adding compost to your grass is a great idea when it needs some extra nutrients to keep it growing healthier. In fact, some people may use compost on their grass without even considering that it may not be best for their situation. So, let’s break down some things to know before you start adding that compost heap to your grass. 

1. Compost Feeds Weeds As Well as Grass

First, compost contains many nutrients that your grass and other plants need for healthy growth. Unfortunately, there is no direct way to specify how the soil uses these nutrients. If your lawn is prone to grow weeds, then compost will also give nutrients to those weeds allowing them to spread throughout your lawn.

Of course, this can happen with grass or plants of any type if weeds are nearby. However, the unwanted growth of weeds can make people hesitate to add compost to their grass. 

Consequently, it is important to address the issue of weeds in your lawn before adding compost, as this can worsen your weed problem. 

In addition to aiding weed growth on your lawn, it is possible that you might even have weeds in your compost pile. Weeds can also sometimes survive the composting process and begin new growth on your lawn when you add compost. If you want to ensure that your compost pile has no weeds, check out my other article for more help: How to Know If Your Compost Is Weed Free?

2. Only Use Compost on Struggling Grass

Another important thing to keep in mind when using compost on grass is to only use compost on grass that is struggling. Using compost on healthy grass can actually create a negative reaction. If your grass is struggling to grow, it requires more nutrients that it is clearly not getting naturally. Compost helps a lot here by supplementing the required nutrients to the plant. Think of it like a booster shot.

However, already healthy grass does not require the extra nutrients that compost provides. So, adding compost to grass that is already getting enough nutrients can cause the grass to become unhealthy and begin to die. You might eventually notice your once green grass turns yellow and brown in some places.

This is indicative that you are overfeeding your grass with nutrients. Compost and fertilizers are usually a mix of multiple nutrients and there is no way for grass to only take the nutrients from compost that it needs and leave the rest. 

So, we are responsible for ensuring our grass gets enough nutrients but not too much. Compost is high in nitrogen, which is great for your lawn and plants. However, excessive nutrients in your soil is almost never a good thing as it leads to a nutrient surplus which has it;s own group of problems.

For example, overloading your grass with nitrogen can cause a phenomenon called “lawn burn,” which means that parts of your lawn are overheating and drying out. 

So, avoid lawn burn by only adding compost to grass that is not currently thriving to ensure you don’t overload it with nitrogen and other nutrients it may not need. Add compost only to grass that needs help for best results. 

3. Avoid Composting Freshly Cut Grass

You should avoid adding compost to your freshly cut grass for many reasons. Majorly, your lawn is most vulnerable immediately after mowing the grass. So, adding compost right away is not the best idea. 

One problem with adding compost right after mowing the lawn is that grass clippings tend to stick around after you finish. Even if you have a mower that picks up the excess cut grass, there is still a good chance you will see it spread in areas of your lawn.

The freshly cut grass clippings sitting on your lawn may be a great source of nitrogen, but when mixed with compost, it can be a bit much for your lawn. You never want to apply your compost with anything underneath it, especially nothing as nitrogen heavy as grass clippings. 

The main reason for this is, like before, a nutrient surplus. Compost already provides nutrients so adding it with grass clippings still fresh on your lawn can cause problems since these clippings will likely decompose under the compost and add a surplus injection of nitrogen to soil.

4. Apply Your Compost Sparingly

Above, we discussed lawn burn and how too many nutrients are bad for your grass. The same applies in this example. Even if your grass clearly needs the help of nutrients that compost can provide, too much of it can cause the same problem.

Adding too much compost can overload your grass with nutrients that it doesn’t need and cause it to “burn”.It can also cause your lawn to yellow or brown with time which are both symptoms of overfeeding. This makes limiting your compost application vital for lawn health. 

Another important reason to limit your compost is to prevent smothering. While compost piles benefit the soil, they can also be quite heavy. Sure, the decomposition process can help the pile be lighter and easier to handle, but it will still have some weight to it. So, adding too much can weigh down your grass and even more importantly, smother it.

To avoid this, it is best to add only a small amount of compost at a time to your grass. 

5. Ensure the Compost Pile Is Ready 

One last thing you want to make sure you do before adding compost to your grass is to ensure it is ready to use. The composting process can take a long time to achieve. Some people lose patience and end up using compost piles that have not completely decomposed. There are many reasons why this is not a good idea. 

If your compost pile is not yet fully decomposed, you may still have chunks of materials like branches or twigs in your pile. These can take a long time to decompose. If you don’t wait for the process to complete, these chunky materials can weigh down your grass and prevent sunlight from reaching the grassroots. 

Not only are chunks of material bad for your grass, but unfinished compost is also bad for it. Until your compost pile finishes the process, it will absorb nitrogen from any source that it can. This means that adding it to your grass too soon can cause a nitrogen deficiency in your lawn. The compost pile will absorb these nutrients from the grass instead of providing them. 

If you want to ensure that your compost pile is ready to use, we have a few ways you can test it. Take a look at my other article: How to Test Your Compost to Know If It’s Ready. Here we provide you with some helpful ways of ensuring your compost pile is ready to go so you don’t risk harming your grass. 

Final Thoughts

Overall, there is nothing wrong with using compost on grass that needs a little help. The main risk comes when using compost on healthy or freshly cut grass. 

It’s also important to always limit the amount of compost you use, to avoid creating more problems than you solve. 

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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