Quack grass, also known as couch grass, is a pesky weed that often invades lawns and gardens. It can be difficult to get rid of this perennial pest, which lays down an extensive system of rhizomes. While you can pull up quack grass, it will keep growing back if you don't remove the roots or starve them to death. It isn't difficult to learn how to keep quack grass out of your flower beds.
Use a garden fork or spade to dig up as much of the quack grass and its roots as possible. Start with patches of the quack grass that are far enough away from your flowers not to interfere with their root systems. Take care not to disturb your flowers' roots. Leave the quack grass roots where they are if you encounter flower roots while digging.
Use a sharp pair of pruning shears to cut back the quack grass you were unable to dig up.
Re-cut the quack grass every time it re-sprouts. Do this as soon as you see it. Repeatedly culling the quack grass prevents it from photosynthesizing and feeding its underground roots. Eventually, the roots will starve to death and the quack grass will be gone for good. It may take more than one growing season to eliminate the quack grass using this process.
Coat the quack grass with a non-selective glyphosate herbicide. Do this in place of repeated cutting-back or in conjunction with it. As soon as the quack grass grows back 1 to 2 inches, pour a little of the herbicide in a disposable plastic container. Dip a small paintbrush in the herbicide and paint it on the quack grass. This method protects your flowers from the herbicide, which will kill them. Repeat at the intervals prescribed by the herbicide's manufacturer.