Can you put down a weed barrier on top of grass?

Updated November 21, 2016

Weed barriers, or landscape fabrics, are used to smother weeds. When used correctly, weed barriers control grass weed growth and prevent weed seeds from germinating. However, installing weed barriers over grass will not ensure success. Gardeners must install the weed barrier correctly, apply mulch and monitor the fabric for sun deterioration.

Weed Barrier

There are 2 different types of weed barriers that gardeners can use on top of grass: plastic and perforated fabric. Plastic weed barriers prevent light and air from entering, while building up heat to smother grass. They are less expensive than landscaping fabric, but will degrade in the sunlight more quickly. Landscape fabric allows air and water to flow through the fabric. To prevent weeds from thriving underneath the material, gardeners must spread mulch over the top.


Spread out your weed barrier next to the grass weed area. Cut the barrier with a sharp blade or scissors so that it covers the entire weed site. Press landscape pins around the perimeter of the fabric. You may need a rubber mallet to hammer the pins in, depending on the hardness of your soil. Avoid using plastic weed-barrier material if the grass is growing on top of tree roots. Use landscaping fabric to allow enough air and water through.


Mulching the top of the weed barrier generates more heat. Gardeners should avoid using an organic mulch, because weed seeds colonise and germinate in the organic mulch material, according to Washington State University. To prevent growing weeds on top of weeds, use an inorganic mulch. The inorganic mulch that you use should not create too many cracks, which can allow weeds to pop up through the small crevices. A mulch like pebbles prevents weeds from growing on top of the fabric or through the mulch.


Weed barriers are not permanent. Over time, plastic and landscape fabric will degrade in the sun. However, mulch slows down the deterioration. Yard pests and weather cause holes in weed barriers; therefore, you must monitor the fabric for holes. Use leftover landscape fabric to patch up holes in the fabric. Keep the weed barrier on the weedy area for at least 6 weeks during the heat of the summer to effectively kill off the grass weeds.

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