Why Does My Mulching Mower Leave Clumps of Grass? (Solved & Explained!)

If you find that the grass is clumping quite regularly when you mow, then it typically boils down to one of two things. Either the lawn will need to be trimmed more frequently, so that too much mulch is not being produced (ideally you should only be cutting the top 1/3 of the grass), or it means that you are mowing the lawn often when the grass is wet.

In today’s article we’ve got a mulching Q&A that will go into some of the do’s and don’ts of mulching to help you avoid this and other pitfalls. Read on for the best practices to get the most out of your mulching!

How do you stop grass from clumping when mowing?

Avoiding grass clumps basically boils down to getting into 3 habits. First off, mow regularly. Regular mowing means that you are only cutting the top 1/3 of the grass and less grass, equals less clumps. Next, keep your blades sharpened regularly – once every 20 – 25 hours.

Finally, don’t mow the lawn when it’s wet if you can avoid it. Wet lawns dull blades faster and clumps are more likely.

Is it OK to leave mulched grass on lawn?

Yes. Mulched grass has been reduced into fine enough pieces that it leaving it on the lawn won’t look unsightly and even better – as it decays it’s going to provide nutrients for your grass. This will help to ensure fuller, thicker grass blades and the fertilizer that you are using is both free and natural. As a bonus, you don’t have to spend time raking it up!

Are mulching blades bad for grass?

No. Provided that you are mowing regularly, mulching blades are a great way to not only keep your grass looking trim and well-maintained, but the additional fertilization from the clippings is very much good for your lawn. Due to the size of the pieces, it decays fairly quickly and gives your grass a continuous source of extra nutrients.

Should I mulch every time I mow?

It’s best to avoid mulching if winter had just ended, so that you can give your grass a little time to revitalize, but once it’s warmed up a bit then mulching every time is fine. The only other exception would be during very hot summers if you haven’t been maintaining the lawn regularly.

This is because an overgrown lawn will produce excess mulch that might cover and heat the soil.

Can you side discharge with mulching blades?

You can, but it is recommended that you upgrade to Gator or other blades which are designed to have better air circulation. Standard mulching blades do not circulate air as efficiently as more specialized blade, as they push down on the grass rather than drawing it up. This can lead to less air-power when bagging or using side discharge.

 Gator blades do not have this problem, as they are designed specially to compensate for this.

Is it better to mulch or side discharge?

That all depends on what you want to do. If you just want to mow the lawn and don’t intend to bag the clippings later, than side discharge is the fastest method for simply getting the job done quickly.

If you intend to mulch, however, you’ll have to run over the clippings multiple times and even then, it won’t be as efficient as mulching – which lets you simply mow and leave the reduced clippings behind you.

Do you sharpen mulching blades?

Yes. Mulching blades should be sharpened, on average, every 20 to 25 hours of work use. Doing so will help to ensure that your blades are always performing at their best. They should also be replaced after approximately 100 – 200 hours of work use, depending on the wear and tear.

You can tell by seeing how evenly they are cutting – once it’s still uneven after sharpening and balancing, then it’s time to replace them.

Does mulching grass spread weeds?

No, mulching won’t spread weeds, provided that you are cutting your lawn regularly. When you cut your lawn on a regular schedule, then each time that you go out with the mower you will only be cutting the top 1/3 of the grass. This means that mulching won’t spread weeds any more than the weeds would spread on their own naturally.

Do you bag or mulch first cut?

For the first cut of spring, it’s recommended that you bag the clippings, rather than simply mulch them and leave them in place. This is because your lawn is just now revitalizing and waiting until the second cut gives it time to warm up and get a little more sunlight to return to a more vital state – at this time, mulching can actually slow this down a little.

What do you do with grass clippings after mowing?

Many recycling centers will now accept organic garden waste for free if you don’t want to simply mulch the clipping and use them to feed your lawn. If you don’t want to do this, you can also use those clippings with some newspaper or dry leaves to make an effective compost pile or to heat up your existing one.

Does mulching grass make it grow faster?

Yes! Mulching grass helps to provide extra nutrients to your lawn as it decays. The end results Is the production of 4% nitrogen, 2% of potassium, and 1% of phosphorous, as well. These ingredients are present in commercial fertilizers and your lawn will make good use of them, growing up healthy, strong, and much more vibrant in color.  

Can you put topsoil over mulch?

You might be able to do this with flowers, but it is not recommended for grass. This would create a thick enough covering and block out enough sunlight that it is likely to slow the growth of your grass and if it’s hot out, it might even overheat the soil. As such, topsoil over mulch is not recommended.

What happens to mulch over time?

Mulch decays naturally over time, converting into useful nutrients such as nitrogen, potassium, and phosphorous. How fast it decays will depend on the density of the mulch that is left in place. Typically with a mulching mower, an approximately 4 inch layer of grass clippings should decay completely within a period of only 2 – 3 months.