Mower leaving clumps of grass clippings

Symptoms

• Visible piles or windrows of clippings after mowing
• Grass looks torn rather than cleanly cut
• Clumps left even in areas mowed slowly
• Deck underside packed with wet debris

Likely causes

• CommonMowing wet grassWet clippings stick together and clog the discharge chute instead of spreading evenly.
• CommonGrass too tall for one passCutting more than a third of the blade height at once produces heavy clippings that clump.
• CommonDull bladeA dull blade tears rather than cuts, producing larger clumping debris.
• PossibleClogged deck undersideBuilt-up wet grass under the deck blocks airflow needed to disperse clippings.

What to do

1. Wait until the grass and dew are dry before mowing when possible.
2. If the lawn has grown very tall, mow it in two passes at different heights instead of cutting it all at once.
3. Disconnect the spark plug wire and scrape out any packed grass from under the deck.
4. Check the blade sharpness and sharpen or replace it if it's nicked or dull.
5. Slow your mowing speed in thick grass so the blade has time to fully process clippings.
6. Consider mulching or bagging attachments if clumping continues in normal conditions.

Tools and parts

• Putty knife or scraper
• Blade sharpening file

When to call a pro

A mower shop can sharpen and balance the blade professionally if clumping continues with a dull blade suspected.

Safety