Quack grass, also known as couchgrass, is a perennial lawn weed that puts down deep regenerative roots. If even a small section of these roots gets left behind when weeding or left untouched by topical herbicides, quack grass will come back the following season. The only way to get rid of quackgrass for good is to remove all of its roots or use a systemic herbicide. Once the grass is gone, maintain the health of your lawn to help it fight off future invasions.
Dig out small patches of quack grass with a trowel. Take care to remove even small parts of the root system. Throw the plants away after you dig them. Do not compost them.
Spray quack grass with a non-selective glyphosate herbicide in the spring when growth is rapid. If you have caught the invasion early and there are only a few patches of quack grass in your lawn, use a product that comes in a hand spray bottle to spot treat them according to the manufacturer's instructions. If your lawn has almost completely been taken over, choose a hose-end sprayer and cover the entire lawn. The grass will die too, but this is the only method to get rid of heavy infestations. Re-spray as necessary according to the manufacturer's instructions.
Dig up the dead quack grass with your trowel.
Re-seed the area to keep the quack grass from reestablishing itself. Spread the seed so there is roughly 1 centimeter between individual seeds. Walk over the bare patch to help the seed make contact with the soil. Keep the re-seeded areas consistently moist with regular watering until two or three weeks after the grass seed germinates. Then resume your regular lawn care maintenance schedule.