One of the biggest misconceptions in lawn care is that leaving grass clippings behind after mowing causes thatch.

In this edition of Healthy Lawns with Dr. Jim, Dr. Jim Wilkinson, founder and owner of SeaScape Lawn Care, explains why that’s simply not true.

In fact, leaving grass clippings on your lawn is usually one of the easiest ways to improve its health.

What Is Thatch?

Thatch is a layer of dead and living organic material that builds up between the green grass blades and the soil surface.

Many homeowners assume grass clippings are responsible for this layer, but that’s not how thatch forms.

Instead, thatch is made primarily of old roots, stems, and other tough plant material that decomposes much more slowly than grass blades.

Grass Clippings Break Down Quickly

Fresh grass clippings contain a high percentage of water and decompose rapidly—often within just a few days.

Because they break down so quickly, they do not contribute to thatch buildup.

Instead, those decomposed clippings become valuable organic matter that benefits your lawn.

Why You Should Leave Grass Clippings Behind

When mowing conditions are normal, returning grass clippings to the lawn offers several advantages:

• Recycles valuable nutrients back into the soil
• Adds organic matter that improves soil health
• Reduces the need to bag and dispose of clippings
• Can return enough nutrients to equal roughly one fertilizer application over time

It’s a simple practice that saves time while helping your lawn stay healthier.

When You Should Pick Up Grass Clippings

There is one important exception.

If your lawn has become unusually tall because of heavy rainfall, vacation, or missed mowings, cutting it may leave behind large clumps of grass.

Those heavy clumps should be removed because they:

• Block sunlight from reaching the grass
• Can temporarily turn the lawn brown
• May eventually contribute to localized thatch problems if left in place repeatedly
• Create an unhealthy environment for the turf underneath

You can remove these clumps by using your mower’s bagging attachment or by raking them up after mowing.

The Bottom Line

For most lawns, leaving grass clippings behind is one of the simplest ways to improve lawn health.

The clippings decompose quickly, return nutrients to the soil, and do not create thatch. The only time they should be removed is when they’re left in thick clumps that can smother the grass.

Following proper mowing practices—and understanding what actually causes thatch—can help keep your lawn greener, healthier, and easier to maintain throughout the growing season.

About SeaScape

For more than 40 years, SeaScape has helped homeowners throughout Rhode Island and southeastern Massachusetts achieve healthier, greener lawns through science-based lawn care programs. From fertilization and weed control to insect management and expert lawn advice, SeaScape provides customized solutions that keep your lawn looking its best year-round.