Why Is My Lawn Mower Leaving Clumps Of Grass?

A well-manicured lawn is the pride of every homeowner. But what happens when your trusty lawn mower starts leaving unsightly clumps of grass behind?

This puzzling issue can be frustrating, but fear not! Understanding the reasons behind this phenomenon is the first step toward finding a solution.

In this article, we’ll discuss why my lawn mower leaves clumps of grass. Ranging from cutting height and dull blades to wet grass and mower deck clogging.

Learn how you can overcome this challenge and maintain a beautifully groomed lawn that will be the envy of the neighborhood.

Clumps of Grass Meaning

When we talk about “clumps of grass,” we are referring to the uneven distribution of grass cuttings left behind by a lawn mower.

Instead of the grass clippings being evenly dispersed, they gather in clumps or piles on the lawn’s surface.

This can make the lawn look messy and untidy. Clumps of grass are often caused by various factors, such as improper cutting height, dull mower blades, wet grass conditions, or clogged mower decks.

Understanding the meaning of grass clumps is essential to addressing the issue and maintaining a well-groomed lawn.

What Are Clumps of Grass Called?

Clumps of grass left behind by a lawn mower are commonly referred to as “grass clippings” or “grass clumps.” These are the accumulations of cut grass that gather in patches on the lawn after mowing.

While some grass clippings can be beneficial as natural mulch or a source of nutrients, excessive clumping can hinder the aesthetic appeal of the lawn and potentially affect its health.

Understanding why clumps form and implementing appropriate mowing techniques can help prevent this issue and maintain a well-groomed lawn.

Troubleshooting and Solutions: Why Is My Lawn Mower Leaving Clumps of Grass?

Problem 1: Excessive Grass Clumping

Excessive grass clumping can be frustrating and leave your lawn looking untidy. Here are some potential causes and solutions for heavy clumping:

  1. Cutting Height: If your mower’s cutting height is set too low, it can cause the grass to be cut too short, resulting in clumps. Adjust the cutting height to a higher setting to allow for better grass dispersion.
  2. Dull Blades: Dull mower blades tear the grass instead of cleanly cutting it, leading to clumps. Sharpen or replace the blades regularly to ensure a clean cut and prevent clumping.
  3. Mowing Frequency: Waiting too long between mowing sessions can result in excessive grass buildup. Increase the frequency of your mowing routine to avoid overloading the mower with large clippings.
  4. Wet Grass: Mowing wet grass can cause clumping as the grass sticks together. Try to mow when the grass is dry, or wait for the moisture to evaporate before mowing.
  5. Mower Deck Clogging: If the mower deck becomes clogged with grass clippings, it can lead to clumping. Clean the mower deck regularly, especially during mowing sessions, to prevent clogs and ensure proper grass discharge.

Problem 2: Uneven Clipping Distribution

Uneven clipping distribution can make your lawn look patchy and uneven. Here’s how to identify the causes and resolve this issue:

  1. Mowing Patterns: Mowing in the same pattern every time can cause uneven clipping distribution. Vary your mowing direction with each session to ensure an even distribution of clippings.
  2. Mower Blade Alignment: Improper alignment of mower blades can result in uneven cutting. Check and adjust the blade alignment according to your mower’s manual to achieve a consistent cut.
  3. Mower Speed: Mowing too quickly can cause the mower to miss spots, leading to uneven clipping distribution. Slow down your mowing speed to ensure thorough coverage.
  4. Uneven Lawn Surface: If your lawn has uneven areas, it can affect the distribution of clippings. Consider leveling your lawn or addressing any unevenness before mowing to achieve a more uniform cut.

Problem 3: Ineffective Bagging or Mulching

Sometimes, bagging or mulching functionality may not work as expected. Here’s how to troubleshoot these issues:

  1. Bagging: If the mower’s bagging system is not effectively collecting clippings, ensure that the bag is properly attached and not overfilled. Clear any debris or blockages in the bagging chute or collection system.
  2. Mulching: Inadequate mulching can lead to clumping of grass clippings. Check that the mulching blades are sharp and properly installed. Avoid mowing when the grass is too tall or wet, as it can hinder effective mulching.
  3. Mulching Plug: If your mower has a mulching plug, ensure it is correctly installed and not obstructed. A malfunctioning or missing mulching plug can result in poor mulching performance.

Problem 4: Recurring Clogging

Persistent clogging of the mower deck can be a common issue. Here are some strategies to address this problem:

  1. Grass Buildup: Regularly clean the underside of the mower deck during and after mowing to prevent grass clippings from accumulating and clogging the deck. Use a brush or scraper to remove debris.
  2. Wet Grass Clippings: Wet or damp grass clippings can easily cause clogging. Try to mow when the grass is dry or allow the grass clippings to dry out before mowing. If necessary, use a leaf blower or rake to disperse any clumps of wet clippings.
  3. Mower Deck Adjustments: Check if the mower deck height is properly adjusted. If the deck is set too low, it can increase the likelihood of clogging. Raise the deck slightly to create more space for the clippings to pass through.
  4. Grass Type: Some grass types are more prone to clumping than others. If you have a particularly clumping-prone grass variety, consider mowing more frequently or using a mower with better mulching capabilities.

Problem 5: Scalping or Damage to Grass

Scalping occurs when the mower cuts the grass too short, leading to bare patches or damage.

To prevent scalping and protect your grass, consider the following prevention and remedies:

  1. Cutting Height: Adjust the cutting height of your mower to the appropriate level for your specific grass type. Different grasses have different recommended cutting heights to maintain their health and prevent scalping.
  2. Uneven Lawn Surface: Address any unevenness in your lawn by topdressing or reseeding. Leveling the surface can help prevent the mower blades from scalping the high spots and damaging the grass.
  3. Mower Wheel Adjustment: Check the mower’s wheel height to ensure they are even and properly adjusted. Uneven wheels can cause uneven cutting, resulting in scalping in some areas.
  4. Slow and Steady: Mow at a slow and steady pace to give the mower blades enough time to cut the grass evenly. Avoid rushing or making abrupt turns, as it can increase the risk of scalping.

Tips for Optimal Mowing

To ensure a well-maintained and clump-free lawn, it’s essential to follow some best practices and techniques during the mowing process.

Here are some valuable tips for achieving optimal results:

Tip-1: Pre-Mowing Preparation

Before you start mowing your lawn, it’s important to prepare adequately to set the stage for a successful mowing session. Follow these steps for effective pre-mowing preparation:

  • Clear the lawn: Remove any debris, branches, or large objects from the lawn to prevent damage to the mower and achieve an even cut.
  • Check the mower condition: Inspect your lawn mower for any signs of damage or wear. Ensure the blades are sharp and in good condition. Replace or sharpen them if necessary.
  • Adjust the cutting height: Set the cutting height of your mower according to the recommended height for your specific grass type. This helps avoid cutting the grass too short, which can contribute to clumping.
  • Trim the edges: Before mowing the main area of the lawn, trim the edges with a string trimmer or edging tool. This creates a clean and polished look and prevents overgrowth from spilling onto the walkways.

Tip-2: Mowing Techniques

Proper mowing techniques play a crucial role in preventing grass clumping and achieving an even and clean cut. Follow these best practices:

Avoid cutting too much at once: Never remove more than one-third of the grass blade’s height in a single mowing session. Cutting too much stresses the grass and increases the likelihood of clumping.

Alternate mowing patterns: Change the mowing direction each time you mow. This helps prevent the grass from leaning in one direction and promotes even growth.

Overlap each pass: Ensure there is a slight overlap between each mowing pass to avoid missed spots and create an even appearance.

Slow down when mowing: Move at a steady pace to give the mower blades enough time to cut the grass evenly. Rushing through the process may result in uneven cuts and clumping.

Maintain a straight line: When mowing in straight lines, use a fixed point at the end of the lawn as a guide. This helps maintain a consistent pattern and prevents crooked cuts.

Tip-3: Post-Mowing Care

After mowing your lawn, it’s important to perform certain post-mowing maintenance tasks to enhance the appearance and health of your grass. Consider the following steps:

Remove grass clippings: If you’re not mulching, collect the grass clippings using a bagging attachment or rake. Removing clippings prevents them from clumping and suffocating the grass.

Clean the mower deck: Grass clippings can accumulate on the mower deck and lead to clogging. Use a brush or scraper to remove any residual clippings to prevent future clumping issues.

Water the lawn: After mowing, water your lawn if it’s necessary. Watering helps the grass recover from the stress of mowing and encourages healthy growth.

Apply fertilizer: If it’s the right time in your lawn care schedule, consider applying a suitable fertilizer to promote strong and lush growth. Follow the recommended application rates for your specific fertilizer.

Inspect for damage or issues: Take a quick walk around your lawn to inspect for any damage or irregularities. Address any areas that may require additional care or attention.


Including cutting height, dull blades, mowing frequency, wet grass, mower deck clogging, grass discharge direction, grass type, and condition.

We also provided troubleshooting solutions for common issues and shared tips for optimal mowing techniques. It is crucial to address grass clumping to maintain a beautiful and healthy lawn.

By implementing the knowledge gained here, you can achieve a flawlessly manicured lawn that will be the envy of your neighbors.


How does cutting height affect grass clumping?

Cutting the grass too low can result in clumping because it puts stress on the grass and inhibits proper airflow. Adjusting the cutting height based on the grass type and growth stage is crucial to avoid clumping. Generally, it’s recommended to follow the one-third rule, where you remove no more than one-third of the grass blade length in a single mowing.

What role do dull blades play in grass clumping?

Dull mower blades tear the grass instead of making clean cuts. This can leave uneven edges and lead to clumping. Regularly sharpening the mower blades ensures clean cuts, reduces stress on the grass, and minimizes clumping. It’s recommended to sharpen the blades at least once a mowing season or more frequently if needed.

How does mowing frequency impact grass clumping?

Mowing too infrequently can cause excessive clumping because the grass becomes too long and difficult to mulch or discharge properly. On the other hand, mowing too frequently can also contribute to clumping, as the grass clippings are too short to disperse evenly. Finding the right balance and mowing at the appropriate frequency for your grass type can help prevent clumping.

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