A triple layer of 80-pound grade roofing paper is also useful as a permanent barrier on areas such as driveways or permanent borders. Both types of mulch can be covered with decorative material such as woodchips or gravel. The quackgrass can grow out around the edges however, so either extend the mulch six to eight feet beyond established quackgrass plants, or monitor the edges for new plants, and treat with glyphosate or glufosinate-ammonium any which emerge from under the mulching. Barriers set down into the soil can prevent this, and also keep the gravel or bark chips from migrating into areas where it is not wanted. The barriers must extend deeper in the soil than the quackgrass roots, probably at least one foot deep.
Quackgrass is very good at what it does, so persistence is the key to managing it.
Montana Weed Management Handbook. Extension Service Pub. Montana State Univ - Bozeman. Bozeman, MT 59717. Pacific Northwest Weed Control Handbooks.