Weed fabric is placed over soil to deter weeds from growing. If you want to place it on an area that is covered with weeds, choose an opaque fabric so no sunlight reaches the weeds. As Sound Native Plants notes, this is useful for controlling weeds that don't respond to herbicides, like field bindweed, hedge bindweed and reed canarygrass.
About this Author
Marie Notnats enjoys learning about new topics and teaching people new skills. She has been writing professionally since 2008. She is a professional horticulturist with a Bachelor of Science degree in horticulture from Brigham Young University. She writes for About.com, Examiner.com, eHow, and assorted gardening blogs.