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Mulching Mower Leaving Clumps – Why And What To Do?

Whether it's summer or winter, you can count on having to mow the lawn at some point during the year. You will be aware that when the clippings clump together, it is a problem that only makes the process more time-consuming and labor-intensive: whether you like to bag the clippings.

Luckily, we've extensively researched this topic and have the answers below!

The table below shows what causes the clumping that your mulching mower leaves and what you should do about it.

 Why It Happens

What You Should Do About It

  • The grass is too wet. 
  • You have long grass on your lawn.
  • Your tool is not sharp enough.
  • Only mow when the grass is dry. 
  • Frequently mow your lawn.
  • Never make cuts larger than a third at once.
  • Consider upgrading your mower. 

Keep reading as we elaborate on each cause of a mulching mower leaving clumps. We'll also discuss how to prepare your mower to do the task properly. Additionally, we'll share tips to prevent the mulch from clumping, the perfect time to mow your lawn, and how often you should do it.

Why Does Wet & Long Grass Cause My Mulching Mower To Leave Clumps?

Grass loves to stick to the grass around it when it is wet, and based on how moist the ground is or how much rain has fallen recently; this can be disastrous for your lawns.

Mulching after lawn mowing fresh hay

The deck of your lawnmower and its catcher will become clogged with matted, soggy wads of grass due to heavy mowers sinking into the grass and whipping up moisture as they cut your lawn.

When these clumps are present on your lawn, they can prevent sunlight and nutrients from reaching the grass below them, harming the health of your property and possibly even creating dead patches.

Additionally, when you haven't mowed the lawns in a while, you could believe that you can cut the grass by setting the mower to its typical cutting height and restoring things to normal. Think again!

Longer grass spreads less than shorter grass, but if too much is applied all at once, your lawns may also turn discolored and uneven.

What Are The Signs That Your Mulching Lawn Mower Is Not Working Properly?

Lawn mower cutting green grass in backyard

The symptoms of an improper mulching lawn mower are pretty obvious. They include:

Clumps Of Grass Clippings

Are a sign that your lawn mower is not mulching correctly or that you are misusing it.

Additionally, it's an indication that you should address the problem since clumps of partially mulched grass clippings serve as a breeding ground for undesirable organisms like lawn fungus and block sunlight from penetrating the soil, which can ultimately kill the grass.

Your Mower Isn't Working Properly

Suppose the grass clippings left behind on your lawn don't differ much from those dropped into your grass catcher when you bag. That is far too coarse of a chop for the clippings.

Another sign is that each time the mower makes a pass, a trail of grass clippings is left behind.

Signs That There Is Something Wrong With Your Mower

Sometimes, problems with clumping can be caused by the mulching mower itself. Here are some of the signs that your mower may not be working correctly:

1. The Blade Used Is Not A Mulching Blade

  • A different kind of blade won't create the ideal environment for mulching. Mulching blades are different from regular blades.
  • Mulching blades have a slightly longer cutting edge and a curved shape that increases their surface area in touch with the clippings and circulates them rather than ejecting them from the deck.
  • On the other hand, a standard blade is made to cut and discharge the clippings considerably more quickly since it is much straighter and aerodynamic in shape, which increases lift (suction action in the deck).

Click here for this mulching blade on Amazon.

2. Clogged Mower Deck

  • Many people believe that the blade of a lawn mower is the only component that matters. However, that is untrue. The cutting deck needs to be kept clean and in good working order at all times.
  • Mulching requires repeatedly circling the deck with the clippings to achieve a fine mulch, but a jammed or broken deck will make this process much less efficient.

3. Your Mower Is Not Designed For Mulching

  • A mower not made to mulch will likely perform poorly if you attach a mulching blade to it.
  • Mulching mowers typically feature deeper decks, which aid in recirculating the clippings and bigger motors and engines, as the mulching operation calls for that extra power.

4. The Blade Is Not Sharp Enough

  • A mulching blade must be sufficiently sharp to perform its function. Clippings won't become mulch if it is on the dull side. You'll probably notice a lot of too-big cuttings.

Click here for this blade sharpener on Amazon.

5. There's A Loose Mulching Plug

  • Likely, your mulch plug isn't correctly fitted if you're observing a trail of grass clippings on one side of your mower.
  • Unmulched clippings are "leaking" through a bit of space on one side and "creating a trail" of their own.

How Do You Know If You're Misusing Your Mower?

Man using a lawn mower, Mulching Mower Leaving Clumps - Why And What To Do?

Here are some of the things you need to remember to execute the mowing task at hand perfectly:

1. It Takes Time

  • One thing to keep in mind is that your mower will have to work much harder when you mulch than when you use it to bag.
  • Since you're asking it to do so, the grass won't be cut into regular-sized clippings that are dropped into the grass catcher and afterward thrown away, but rather into tiny clippings.
  • Because of the additional time required to cut the grass numerous times, it may appear that your mower isn't mulching correctly if you move through your lawn quickly. You're not allowing it enough time to mulch correctly, which is the issue.

2. Let The Ground Dry

  • It's a recipe for disaster when mulching, and the lawn is moist. Wet grass is very fond of clinging to other pieces of grass and will stick to anything.
  • When mowing in rainy weather, clumping is a necessary evil, but it can give you the impression that your mower isn't mulching correctly.

3. Take It Easy

  • The best approach to ensure that your lawn has great, huge clumps of grass throughout it is to mow it when it is particularly long. No matter how efficient a lawn mower is, cutting too much grass at once can result in too many clippings.
  • Never remove more than one-third of the height of your grass at once. It damages the lawn and will clog your mower, particularly during mulching.
  • When you do this, a considerable amount of clippings will be spread throughout your mower's deck. There will be too much grass for your blade to cut effectively, putting strain on your mower's engine or mower.

How Often Should You Mow Your Lawn?

Man mowing the grass

Mowing the grass maintains your lawn's health and keeps it neat.

The timing of this changes depending on the grass on your lawn, but you won't need to mow your lawn as frequently during the dormant season as you do during the active growing season.

The key to maintaining a healthy, green lawn is to keep your grass at the right height and to avoid removing too much at once.

The frequency of mowing depends on the grass growth rate and your lawn's desired height. Mowing your lawn once a week should be plenty to keep it healthy during the growing season.

If necessary, you might lower the cutting frequency to every other week throughout the remaining time.

When Should You Mow Your Grass?

Mowing the grass

During the growing season, grass requires the most cutting. While cool-season grasses thrive in the spring and fall, warm-season grasses bloom in the summer.

If they are not damp and heavy, leave the grass clippings on the lawn to fertilize it. These clippings might have a nitrogen content of 3–4% and a potassium content of 2.5–3.5%.

Additionally, when the grass is dry in the morning, try to mow your lawn at that time. If not, mowing should be done late afternoon, around 4:00.

To Finish

To avoid clumping your mowed mulch grass, ensure you do the task while your lawn is dry. Also, ensure that your tool is adequately equipped to do the job. Check if the blades aren't dull and if you use the right equipment.

Furthermore, make it a routine to mow your lawn frequently, and to prevent clumping, don't chop more than 1/3 of the grass' height.

Lastly, mowing your lawn takes time. Take it easy and take your time while you do the job. Rushing only makes you prone to making more mistakes along the way.

Made it this far? Check out these related articles below:

What Angle to Sharpen Lawn Mower Blades

Can Mulching Leaves Kill Grass?