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How Does Mulching Help To Control Weeds?

Mulch provides several key benefits in the garden, such as keeping the soil moist and regulating its temperature. If weeds are destroying the look of your garden, fortunately mulch can keep them away too. This means weeds won't steal your plants' water and nutrients leading to healthier looking plants.

But from a scientific standpoint, how does mulch actually prevent or suppress weed growth? Like any plants, weeds need light to germinate and grow, which means blocking sunlight from the soil it effectively prevents them from developing. By blocking sunlight from the soil, it can therefore, prevent weed germination and photosynthesis. The depth of the mulch is also important as the mulch you use. Studies have shown that the best depth of organic mulch to lay is 2-4 inches. Too low a depth will not block sunlight effectively, and too big a depth will prevent oxygen and moisture from reaching plants roots.
There are two main types of mulch to use in your strategy against weeds: organic and inorganic, which will have different effects on the soil and other nearby plants.

Organic mulches can keep weeds at bay while slowly releasing nutrients to your other garden plants. Chunky mulches are best for shading the soil; examples include bark or wood chips that are slow to decompose, leaves that are quick to decompose and grass clippings that provide lots of nitrogen to green plants and lawns. Straw or hay is also effective at shading the soil to prevent weed germination — but some hays have weed seeds in them.

If you have a heavy weed problem in your yard, some inorganic mulches are more effective than natural mulches. The most successful is black plastic, which completely blocks sunlight to your soil. However, it can increase the soil temperature more rapidly and deprive soil of oxygen, which may end up damaging the roots of some plants. A lighter option is newspaper, which also keeps sunlight from the soil. To keep it from blowing away in the breeze, you'll need to put something on top of it, such as an organic mulch.