Should I Leave Grass Clippings on Lawn: What Can Happen?

By   | Last Updated :   October 15, 2022 | Filed In :   DIY & How To

So you’ve mowed the grass and it’s covered in a fresh layer of grass clippings, but should you leave them on the lawn? As every gardener knows, raking the grass cuttings after every cut is a bit of a palaver. You may have heard contradictory things about leaving grass cuttings on the lawn and wonder whether you can save yourself some precious time by just leaving them.

We’ve put together a handy guide about the pros and cons of leaving grass clippings on the lawn so that you can make up your own mind.

should you leave grass clippings on lawn

Are grass clippings good for your lawn?

Grass cuttings are rich in nitrogen and potassium and as they break down on the surface of the lawn, they release water and valuable nutrients back into the soil. This biodegradable mulch can provide as much as a quarter of the nutrients that a lawn requires. So the good news is that it’s safe to leave grass cuttings to decompose on your lawn, at least some of the time.

Because chopped grass blades are so fine, they will take around a month to decompose. If you have a mulching mower, it’ll chop the grass blades into a super fine mix that’s perfect for the lawn, the cuttings won’t sit around in clumps and the grass will break down more quickly.

grass clippings on lawn

Image credit: @aerobincomposter

Should you leave grass clippings on lawn?

Yes, you can, but it’s better to leave grass clippings on the lawn at certain times of the year. You don’t need to leave the clippings after every cut, especially during the summer when you’ll be mowing the lawn at least once a week. Take into account the condition of your lawn and whether or not you think it would benefit from a regular dose of grass clippings, or if a monthly nutrient boost is enough.

Grass cuttings will decompose more quickly during the warmer months of the year, so you can leave the cuttings on the grass during spring and summer, but remove them after the first and last grass cuts of the year

As well as providing a welcome nutrient boost, leaving grass clippings can also help to prevent weeds from establishing. As good as grass clippings can be for a living lawn, if you’re wondering whether putting grass clippings on bare spots helps grass grow, the answer is, sadly, no. But, you can always overseed the bare spots!

When to rake grass clippings

Grass clippings can be hugely beneficial to the existing lawn and will provide a nutrient boost, helping the grass to grow and strengthen, but there are times when bagging or raking them up is a better option:

When to leave grass cuttings

Unless your lawn is in terrible condition, in which case you probably wouldn’t have many grass cuttings anyway, it’s usually fine to leave the grass cuttings on the lawn at certain times of the year, as long as your grass is healthy, dry and relatively weed-free. 

Can there be too many grass clippings on the lawn?

If you’ve left it a little too long between grass cuts, the longer blades can create a thick layer of clippings after mowing. Too much grass clippings on the lawn will block the airflow to the living grass underneath and increase the risk of fungal lawn diseases such as brown patches, powdery mildew and Pythium blight.

Although dead grass won’t generally kill grass, it can be a factor in damaging lawns if it affects the airflow, causes more weeds to grow or spreads disease.

What to do with picked-up grass clippings after mowing?

thin layer of grass cuttings to your compost heap

Add a thin layer of grass cuttings to your compost heap. Image credit: @joclarkcookingetc

Compost them

If you’ve got a garden compost heap, and your lawn is disease-free, the best thing to do with grass cuttings is to compost them. Because of their high nitrogen content, grass clippings are the perfect addition to a homemade compost heap. It’s best not to add them in one thick clump because they’ll smell pretty bad when decomposing, instead, layer them with other organic matter to help the airflow.

Recycle them

If you don’t have space for a compost bin, just pop the clippings into your green council waste bin.

Use them as mulch

You can use grass cuttings as an effective weed suppressant (as long as they aren’t from a weedy lawn). Place the cuttings at the base of hedges or trees, or use them as mulch in garden beds.

grass clippings can make a perfect mulch

Grass clippings can make a perfect mulch. Image credit: @sams.allotment.revamp

Top Tip: Don’t be tempted to use grass cuttings as animal feed, fresh cuttings, in particular, can cause digestive problems and even choking in many animals.

How to clean up grass clippings

Cleaning up grass clippings can be quite labour-intensive. The best way to collect them is to use either a grass box that fits onto your lawnmower or a tow-along lawn sweeper which will collect the cuttings, ready for you to compost them.

You can also use a good, old-fashioned rake, there are many different designs and, although it’s hard work, it’s a great way to get those feel-good endorphins flowing!

So, should I leave grass clippings on the lawn?

Grass cuttings from a healthy lawn can be left to break down during the warmer months of the year. As long as the cuttings aren’t too thick, which will affect the airflow to the living lawn beneath, there’s no reason why you shouldn’t leave your clippings to feed the lawn. 

Remember that clippings from a mulching mower are the gold standard for lawn cuttings. Their finely chopped texture means they’ll quickly get to work without any risk of damaging the lawn, this is especially important if your lawn is in less-than-perfect condition.

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