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will plastic keep weeds from growing

Will plastic keep weeds from growing

Love it or hate it, weeding your garden is a chore you have to do regularly. You’ve likely spent time and effort to stop weeds if you have a large garden space. Here, we’re myth busting the use of landscape fabric. By definition, it’s permeable and it’s not a permanent product.

Linda Chalker-Scott, Ph.D., extension horticulturist and associate professor at the Puyallup Research and Extension Center, Washington State University, is our expert resource.

Landscape fabric can be a temporary solution for an area but it's clearly not a long-term or permanent solution to stop weeds.

Thin plastic sheets can kill weeds and prevent future weed growth in your vegetable or ornamental garden beds. Solarization methods use plastic to prepare new beds, while mulching with plastic stops further weed growth after you plant. Plastic also retains soil moisture so you can use less water, while warming the soil in cool weather.

Soil Solarization

Clear plastic can stop weeds before you put in your new garden bed. Sunlight passes through the plastic, and the heat becomes trapped, effectively cooking the weeds and seeds near the soil surface. You must till in any fertilizer or amendments before you solarize, because tilling afterward can turn up deeply buried but still viable weed seeds. After moistening the soil, cover the bed with 2- to 4-ml plastic. It takes four to six weeks of intense sunlight to kill the weeds, so use this method during the hottest, sunniest part of summer.

Plastic Mulch

Water sometimes pools on the surface of black plastic mulch. Poking a few holes allows the water to drain into the soil, but too many holes makes it easier for weeds to penetrate through the plastic and invade the garden bed. Plastic also warms up the soil. Although this is beneficial in cool weather or early in the season, it can stress plants during hot weather. Covering the plastic with a 1-inch layer of straw helps cool down the bed. If you use plastic in an ornamental garden, a thin layer of bark mulch can camouflage the unattractive plastic. Dispose of plastic at the end of the growing season, because it won’t decompose in the garden or in a compost pile.