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Weeds and Your Garden

Block Weeds with Plants and Mulch

You can prevent light from reaching weeds for a season, while your plants get established—or, in severely weedy situations, for a year or more.

Advantages of living plants and mulches

The leaves of living plants prevent light from reaching the soil. Try wide-canopy plants—such as closely planted broccoli—or dense ground covers (for example, woodruff or drifts of daylilies or hostas).

Cover crops or "living mulches," such as clover, have many benefits. Some interfere chemically with weed growth; sorghum sudangrass, winter rye, and fescues, for example, excrete substances from their roots and shoots that suppress weeds. Many gardeners recommend a season or more of cover crops to minimize weeds in newly planted sites. A dense canopy of buckwheat blocks weeds and is pretty, too. Tilling under cover crops also increases the organic matter content of the soil.

Organic mulch

A 4-inch thick layer of shredded bark, straw, leaves, wood chips, or several other organic choices can prevent seeds from germinating. You might also consider laying down sheets of newspaper beforehand.

Plastic or black landscape fabric

using landscape fabric to thwart weeds
Preparing beds with cardboard or black plastic can thwart quackgrass and other plants that reproduce by underground runners, but these weeds are persistent.

You can lay black plastic or landscape fabric around established flowers, shrubs, or vegetables to prevent weeds from emerging near them. Alternatively, lay down the sheeting on newly prepared beds and poke holes into which you’ll plant. Try to prevent weeds from emerging from the edges of those holes. When planting shrubs or trees with root systems that will expand outward, beneath the sheeting (versus straight down), use landscape fabric that allows water—but not light—to penetrate. Certain synthetic fabrics can be expensive and difficult to install and remove, especially once weeds have rooted into them or sunlight has degraded them. They also separate the decomposing mulch from the soil organisms.

Some gardeners place chopped leaves or other organic material under the plastic. Once the plastic is removed, the soil generally has better tilth, or texture, from the activity of soil organisms and the decomposition of organic matter.