Grass clippings won’t kill existing weeds in your lawn, but a 3–4 inch deep (7.5–10 cm) layer of dried clippings can be used as a weed-stopping mulch in gardens and flower beds. Grass clippings used as mulch block sunlight from reaching the ground, killing weeds as they attempt to sprout. For best results, remove existing mature weeds before laying mulch.
Can You Use Grass Clippings as Mulch to Stop Weeds?
The grass clippings produced by mowing can be repurposed as excellent garden mulch. Grass clipping mulch not only suppresses weeds, but also helps the soil retain moisture, insulates the ground against intense heat and cold, and gradually decomposes, returning organic matter to the soil.
- Grass clippings make an excellent garden mulch.
- A 3–4 inch deep layer of mulch stops weeds from sprouting your garden.
- The mulch layer prevents any weed seeds that blow into the garden from reaching the soil and taking root.
- Grass clipping mulch helps retain soil moisture to reduce watering needs.
- Grass clippings work as fertilizer. As it decomposes, the organic materials in the mulch layer feed your garden.
Grass blades are the equivalent of a slow-release fertilizer. They contain 4% nitrogen, 1% phosphorus, and 2% potassium. As your grass mulch layer breaks down over the course of 2–3 months, it will return these nutrients to the soil. Lawn clipping mulch performs a dual purpose as garden fertilizer and mulch.
How to Use Grass Clippings as Weed-Stopping Mulch
When using grass clippings as mulch, it’s essential to use grass clippings that have been given the appropriate time to dry. Wet grass clippings fresh from your lawn mower will release heat as they dry, which can damage the plants in your garden. For best results, leave the grass clippings to dry for 1 day after mowing. Then, rake them up and use them as mulch.
- Allow grass clippings to dry in your lawn for 1 day before raking them up for use as mulch.
- Spread grass clippings 3–4 inches (7.5–10 cm) deep, to suppress weeds and prevent weed seeds from sprouting.
- Small annual weeds can be smothered with a good mulch layer
- Do not cover desirable plants with mulch. They may be smothered.
A 3–4 inch layer of grass clippings will serve as an effective weed barrier that keeps new weed growth from invading your garden. Small annual weeds will be smothered by mulch and die. Established perennial weeds, such as dandelion, may find a way to survive and poke through the mulch. These should be removed before mulching. Just make sure none of your garden plants are buried beneath the mulch layer.
Mistakes to Avoid When Using Grass Clippings to Stop Weeds
Do not use grass clippings as mulch if your lawn has been treated with herbicide in the last 60 days. Systemic herbicides used to kill weeds attack broadleaf plants, meaning they kill both weeds and garden plants. If you use lawn clippings that were recently sprayed with a herbicide that kills broadleaf weeds, you run the risk of killing the plants in your garden by introducing herbicides.
- If your grass has been treated with herbicide in the last 2 months, do not spread it in your garden.
- Do not spread grass clippings from a weedy yard in your garden bed.
- Avoid using fresh grass clippings as mulch.
If your lawn has a lot of weeds, don’t use the grass clippings to mulch your garden. Weeds in the grass clippings can drop weed seeds in the garden and cause more harm than good. Weedy grass used as mulch can introduce lawn weeds into your garden. Similarly, do not use fresh grass clippings as mulch. Grass clippings that have just been through your mower blades will release a lot of heat as they go through the initial drying stages. If the grass clippings are piled near the base of your plants, the heat they release can damage roots, stems, and leaves.
Do Grass Clippings Help Control Weeds?
If used as mulch, weed-free grass clippings suppress weed growth in gardens. The mulch barrier smothers weed seeds that sprout, killing them before they break through and reach the sun. Additionally, any weed seeds that enter the garden will be trapped in the mulch, preventing them from reaching the soil where they can sprout and take root. Use the cut grass left over from mowing as free mulch that keeps your garden happier and healthier the natural way.