Landscape Fabric Or Black Plastic
In all landscape planting beds you should have some form of weed barrier between your bedding material and the soil. When properly installed, these weed barriers prevent the roots of weed seeds from reaching the soil and gathering nutrients.
Black Plastic Weed Barrier
The best features of black plastic, and the reasons for its continued popularity, are its abilities to suppress weed growth and retain soil moisture. Unfortunately, although black plastic prevents water from exiting the soil, it also prevents water from entering the soil. Plastic is not recommended for poorly-drained areas as it may cause the soil to remain too wet, which could result in root disease problems. If exposed to sunlight, black plastic is broken down fast, losing its effectiveness as a weed barrier. Some thin or poor grades of plastic can have problems with cracking over time, creating holes or rips where weeds can grow.
Landscape Fabric Weed Barrier
These woven and nonwoven fabrics of polypropylene or polyester are an improvement over traditional black plastic. They not only block weed growth and reduce surface evaporation but also allow water, fertilizer, and oxygen to penetrate easily through to the soil. They are used more frequently as mulch and stone underliners, enhancing the weed-suppressing ability of the mulch while separating the mulch and soil. Landscape fabrics need to be fastened down to the soil with special staples so it will not be pushed up by perennial weeds.
Clear plastic is not recommended as a weed barrier. Clear plastic will not suppress weed growth because light penetrates the film and raises the soil temperature, which may result in an increased growth of weeds in early spring.