Winter & Quack Grass

Seasonal Pattern

• Quack grass remains underground during the winter, but it starts to push up in the early spring, around March. It grows most during the cool season. The green tops start growing more slowly in the hottest part of summer. However, the rhizomes spread out sideways all during June, July and August. The old grassy shoots die back in the fall. At that time, the rhizomes put out new primary shoots. The next winter, the new buds again become dormant until spring. Quack grass flourishes especially well when the soil remains undisturbed all year, for example among perennial plantings.

General Control Techniques

• Frost can kill quack grass rhizomes in the winter. Except for during the coldest weather, you must expose them to the frost by digging them to the surface. In summer, dig out the rhizomes and let them dry in the sun. If you slice the rhizomes into pieces without removing them, the plants will multiply. Slice off new grassy shoots to prevent photosynthesis and starve the rhizomes. Keep the lawn mowed around the edge of the garden so that seeds cannot blow in. Don't mulch flower or vegetable beds with grass clippings that contain quack grass. Application of other mulches will help control the small quack grass shoots, but mulch cannot kill the rhizomes.

Winter Planting

• Competing winter plantings help choke out quack grass during its dormant season. The University of Minnesota Extension recommends planting winter rye plus crown vetch, followed by a covering of buckwheat. The University of Maine Agricultural Program recommends winter rye and hairy vetch or oats and peas. It also recommends continuing to plant a winter cover in successive years to prevent the quack grass from returning.

Chemical Control

• The best chemical remedy for quack grass is an herbicide made with glyphosate, such as Monsanto's Roundup, according to the University of Minnesota Extension. Do not use it during the winter dormant season. Apply it only during the growing season on a day with still air. First apply a nitrogen fertilizer to activate the buds so that glyphosate works better. Use the pesticide when rain is not predicted for at least 48 hours. Do not cultivate the area for two weeks afterward, and reapply it every four to six weeks. Herbicides with fluazifop also kill quack grass among perennials. However, follow package directions to avoid damaging neighboring plants or harvesting fruits or vegetables before they are safe. Use gloves and protective clothing when applying pesticides.