Quack grass (Elytrigia repens)

Common weeds at a glance

Also known as couch grass or devil's grass, quack grass is an aggressive perennial that invades lawns and gardens in most of the country. It can reach 3 feet tall, but it stays much lower in mowed areas. It produces an extensive mass of long, slender, yellowish white branching rhizomes (underground stems) that can spread laterally 3 to 5 feet.

Because it reproduces readily from even small pieces of rhizome left in the soil, quack grass is difficult to manage. Before planting, thoroughly dig the area and remove all visible pieces of rhizome; this will slow the weed's growth for a few years. You can also suppress quack grass by smothering; leave the cover in place for at least a year.

For chemical control, use selective herbicides containing fluazifop-butyl or sethoxydim; these will suppress quack grass and most other grasses. Or use a nonselective herbicide containing glyphosate, taking care to avoid contact with desirable plants.