The advantages of clipped grass mulch are, unfortunately, few are far between. However, if used in combination with other mulching materials in the proper amounts, grass mulch can benefit your plants.
What Are the Dangers of Grass Mulch?
Grass mulch can be quite a bother if it is not prepared and used properly. If it has been sprayed with insecticides, it can be harmful to your plants and soil. Furthermore, if you use it alone and not in concert with other mulching materials, it can become matted rather quickly. This will simultaneously block water from being able to flow through and reach the soil and create excessive heat and odor as it decomposes. It will also brown quickly adding a possible eye sore to your garden or landscape.
How Do I Make Grass Mulch Beneficial?
Because grass is composed of so much water, it can provide fast decomposing times to compost. This may or may not be an advantage. Always combine grass with other mulching materials that have already decomposed for a time. Unlike more common mulching materials like wood chips that take at least two years to get to an effective and useful state, grass mulch takes but a few weeks. So add some grass to other materials that you plan to use as mulch such as shredded twigs, wood chips or leaves.
Remember only to add a small amount of grass; about ten percent of the whole of your mulching material. This will add fluffing material to the grass, preventing it from becoming matted. Water will be able to penetrate and the compost will remain open to aeration. Another reason to hold the grass to 10 percent is that higher grass levels could cause faster decomposition and result in much higher soil temperatures as decomposing grass can become quite warm.
It isn't advisable to attempt to mix grass with other quickly decomposing materials such as food scraps. More often than not this is simply an invitation for insects and other bacteria to grow. Moreover, it could easily spread diseases to the very plants you are mulching to protect.
While grass is not the best material for mulching if you mix it with other mulching materials in small quantities, you should be able to avoid the problems usually associated with grass mulch and instead reap the few benefits it offers. And since it comes from free grass clippings, the price is right.