Quackgrass
Grassy weed
Quackgrass (Elymus repens, formerly Agropyron repens) is a cool-season perennial grass and one of the most persistent weeds in North American lawns, gardens, and cropland. Gardeners and growers notice it because it spreads aggressively underground and comes back year after year, often taking over a bed or patch of turf before it is recognized.
How to identify it
The leaves are flat, rough or slightly hairy on the upper surface, and blue-green to dull green, usually 1/4 to 1/2 inch wide. A key feature is the pair of small, clasping, claw-like appendages (auricles) that wrap around the stem where the leaf blade meets the sheath. It grows upright to 1 to 4 feet tall and produces a slender, wheat-like seed spike at the top of the stem. Below ground it forms long, straw-colored, sharp-tipped rhizomes with a whitish, jointed appearance that can spread several feet in a season.
Where it grows
Quackgrass thrives in disturbed soil, garden beds, lawns, field edges, roadsides, and cropland across the cooler regions of the United States, especially the Northeast, Midwest, and Pacific Northwest. It grows most actively in spring and fall and tolerates a wide range of soils and moisture levels. It spreads mainly by its extensive creeping rhizomes, and also by seed, so even small root fragments left in the soil can start new plants.
Why it is a problem
Quackgrass competes strongly with crops, vegetables, and turfgrass for water, light, and nutrients, and its dense rhizome mat can crowd out desirable plants. The rhizomes also release compounds that can suppress the growth of nearby plants, reducing garden and crop yields. Because it regrows from tiny root pieces, it is very hard to eliminate once established and can quickly reclaim cleared ground.
How to manage it
The most reliable non-chemical approach is repeated, thorough removal of the rhizomes: dig carefully and sift the soil to lift out as much of the underground root system as possible, since fragments left behind will resprout. Smothering an infested area with a thick layer of mulch, cardboard, or an opaque cover for a full growing season starves the rhizomes of light and weakens them over time. In lawns, keeping turf dense and healthy through proper mowing height, adequate fertility, and good soil helps crowd out new seedlings and slows invasion. Prevent spread by cleaning soil and rhizome pieces off tools, boots, and tillers, and by not composting fresh rhizomes, since tilling alone chops them into new plants rather than killing them.
Commonly confused with
Quackgrass is often confused with tall fescue and with young crabgrass, but the clasping auricles at the leaf base and the long, sharp, spreading white rhizomes set it apart. Crabgrass is a warm-season annual with no rhizomes, and tall fescue grows in clumps rather than running underground.
General guidance for US lawns and gardens, focused on prevention and non-chemical control. For a confirmed identification and options specific to your area, contact your local Cooperative Extension office. Page updated Aug 4, 2026.