Do I Have to Spray Weeds Before I Mulch?

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Mulching helps prevent weed growth and makes weeding easier.
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Mulching is one way to control weeds in your garden or landscaped areas. You may wonder, "Do I have to spray weeds before I mulch?" Simply putting down a layer of mulch won't stop those weeds from returning or continuing to thrive in your garden or landscaped area. Clearing, spraying and mulching can make it significantly more difficult for weeds to wind up in your garden or landscaped areas.


A layer of mulch makes an ideal home for weed seeds and spores carried by the wind or introduced to the mulched bed, so spraying is a good idea.

Prepare the Area for Mulch

Before mulching, prep the area with a garden edging tool to create a sharp boundary. This will help keep weeds and grass from creeping into the area that has recently been cleared.

After it is all laid out neatly, mulch will settle and fall onto the grass, concrete or surrounding material. The bits of mulch can create a mess and give the garden an untidy appearance. Use a spade to dig a small trench of about 2 or 3 inches around the edge to give the mulch room to roll.

Spray for Weeds Before Mulching

While a few straggly and thin weeds just getting a start can be plucked from the area before mulching, established weeds need to be pulled and the area sprayed to ensure roots and spores don't return and find a way through the barrier of mulch.

Before mulching a new bed, pull all weeds from the area. Spray a weed killer on the area where the weeds were pulled. Be careful not to overspray and hit the foliage of nearby plants' leaves or roots with the weed killer.

An organic weed killer can be used for vegetable gardens. To be safe, wear gloves and safety goggles when working with weed killer. A particle mask will help keep any fumes from irritating your nose or mouth.

Second Layer of Weed Killer

After pulling weeds and spraying the area, apply a pre-emergent weed killer over the bed. Water in the pre-emergent, making sure it won't affect healthy plants, trees or shrubs. Always check the label to make sure it works well for the landscaping and plants that surround or are in the area where it will be applied.

The pre-emergent weed killer will form a barrier within the soil and keep new weeds from sprouting up from underneath the layer of mulch. This should last about six months before it needs to be refreshed. Finally, a layer of landscape fabric is designed to allow air movement for plants but to block weeds from sprouting from below.

Mulch After Spraying

The space between the base of the plant and the layer of mulch allows the plant to breathe. The air movement is important for the plant's growth, so don't pack mulch up against the base of plants' stems. A layer of fresh mulch can be applied over old mulch that has been tilled and loosened but don't apply too much. A good 2 inches of mulch is all you need.

A thicker layer of mulch will prevent essential oxygen from reaching the soil and will eventually suffocate the plants. This will keep weeds from sprouting but will also kill any healthy plants in the area. If you've applied too thick of a layer of mulch, then just thin it out.


Kimberley McGee is an award-winning journalist with 20+ years of experience writing for a variety of clients, including The New York Times, Las Vegas Review-Journal Home section and other national publications. As a professional writer she has researched, interviewed sources and written about home improvement, interior design and related business trends. She earned a B.A. in Journalism from the University of Nevada, Las Vegas. Her full bio and clips can be viewed at

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