Mulching with grass clippings adds organic matter and nutrients back to your lawn. However, using fresh clippings as mulch also comes with some potential downsides.

In this guide, our expert outlines what you should and shouldn’t do with your grass clippings. Here is what you need to know about mulching with grass clippings.


When Not to Mulch with Clippings

Most of the time, when you mow, leave grass clippings on the lawn. Mulching blades on lawnmowers chop up clippings into tiny pieces that break down rapidly. The fresh clippings decompose quickly and release nutrients back into the soil. 

However, sometimes bagging clippings makes more sense.

Bag them when you mow an overgrown lawn for the first time. Long grass clippings clump together and smother grass if left on the lawn.

If you have to mow when the grass is wet or if it has many weeds, it’s also best to use a bag. Wet clippings decompose slowly, and weeds will spread seeds if left on the lawn.

Today’s Homeowner Tips

Bag if you think chemicals contaminated the clippings. If you recently applied weed killers, fertilizers, or insecticides, bagging prevents these chemicals from going directly into the soil. In these cases, consider bagging the clippings and then using them as pre-treated mulch in your garden beds. 


Advantages of Grass Clippings as Mulch

Using grass clippings as mulch offers some potential benefits.

Clippings contain nitrogen, phosphorus, potassium, and other useful nutrients that can feed garden plants as mulch breaks down. You can reduce the need for chemical fertilizers.

Grass clippings are a free waste product available anytime you mow. A single mowing can generate enough clippings to mulch small garden beds.

A thick layer of clippings blocks light from reaching weed seeds and smothers small weed seedlings attempting to sprout. This natural mulch barrier reduces the need for you to use herbicides.

Mulching with clippings helps soil retain moisture. As clippings decompose, they improve soil structure to enhance water retention. Less frequent watering saves you time and money.


Disadvantages of Clippings as Mulch

While using grass clippings as an organic mulch has benefits, remember that it has some potential drawbacks. Green clippings decompose quickly, especially in hot weather, and can leave plants under-mulched if you don’t mix them with new clippings consistently.

grass clippings
Image Credit: Canva

Applying more than 1 inch of fresh clippings can cause the trimmings to mat and prevent water and air from reaching plant roots.

Also, decomposing green materials generates heat. Too thick of a layer can burn plant roots and crowns. Ideally, limit each addition of mulch to 1 inch.

Any weed seeds that mix into your clippings can sprout later in your garden or wherever you throw your organic mulch. Remove weeds from your lawn before bagging them for mulch or leaving them to mix back in with your lawn.

Similarly, fungal diseases and pests like grubs may inadvertently transfer to your garden plants with your new grass mulch.

Finally, clippings may contain herbicide or fertilizer residues that could damage garden plants. Avoid using clippings after chemical applications.


Best Practices for Mulching with Grass Clippings

Follow these tips to use grass clippings successfully and safely as mulch:

  • Let clippings dry and brown completely before spreading them in the garden. This prevents matting, reduces heat buildup during decomposition, and gives weed seeds time to die. (A tip: Spread clippings in a thin layer on a tarp or concrete driveway. After one to two weeks, they should be ready to use as mulch.)
  • Apply clippings in layers 1 inch deep or less, allowing them to dry between applications to prevent matting and smothering plant crowns. (Tip: Only apply 1 inch of dried clippings at a time before letting them dry out for a few days. Adding too much at once can suffocate plants.)
  • Pull weeds from your lawn before you mow to reduce weed transference. Target broadleaf weeds with herbicides at least one week before generating clippings.
  • Avoid using clippings from lawns recently treated with weed killers, fertilizers, or insecticides. Wait at least two mowings after any chemical applications.
  • Monitor plants for any pest outbreaks after applying grass clippings mulch. Treat pests immediately to avoid spreading issues.
  • Rotate grass-clipping mulch with organic mulches like shredded leaves or wood chips. This practice provides a variety of nutrients and prevents matting issues.

Mulching with grass clippings can benefit your garden and reduce expenses for mulch and fertilizer. However, fresh green clippings present some risks in terms of matting, heat buildup, and weed propagation that require careful management.

I find that the best approach is to leave clippings on your lawn whenever possible. Sometimes, you must bag clippings. With proper drying and layering techniques, along with preventive weed and pest management, you can mitigate the modest risks of grass clippings mulch. Consider the pros and cons to decide if grass clippings mulch fits into your garden plans.


FAQs About Mulching with Grass Clippings

How long should I let grass clippings dry before using as mulch?

In my experience, you should allow clippings to dry for one to two weeks after mowing before using as mulch. They should be brown, dry to the touch, and no longer give off a green grass odor.


Should I avoid using clippings from the first mowing of spring?

You should avoid using any clippings from the first mowing of the spring as mulch. Mow two or three times before you collect the clippings for mulch.


How do I calculate how much mulch I’ll get from mowing my lawn?

The formula for figuring out mulch volume is that 5,000 square feet of lawn area yields 1 cubic yard of clippings.


Can I compost grass clippings instead of using them as mulch?

You can always compost your grass clippings instead of using them for mulch. Mix the clippings with dry leaves or straw in a 50/50 ratio for balanced composting. Avoid thick layers of green clippings alone, which may rot into a smelly, slimy mess. Also, turn the pile regularly.


Should I shred leaves in the fall to mix with grass clippings?

Adding shredded leaves is ideal to mix with grass clippings. Leaves help the grass decompose faster and mix evenly with nitrogen-rich clippings for a balanced, fine-textured compost or mulch.


Editorial Contributors
avatar for Coty Perry

Coty Perry

Expert Writer & Reviewer

Coty Perry is a lawn and garden writer for Today’s Homeowner. He focuses on providing homeowners with actionable tips that relate to the “Average Joe” who is looking to achieve a healthier and greener lawn. When he isn’t writing he can almost always be found coaching youth football or on some trail in Pennsylvania in search of the next greatest fishing hole.

Learn More

photo of Sabrina Lopez

Sabrina Lopez

Editor

Sabrina Lopez is a senior editor for Today’s Homeowner with over 7 years of writing and editing experience in digital media. She has reviewed content across categories that matter to homeowners, including HVAC services, home renovations, lawn and garden care, products for the home, and insurance services. When she’s not reviewing articles to make sure they are helpful, accessible, and engaging for homeowners like herself, Sabrina enjoys spending time with her family and their two parrots.

Learn More