What Is Quackgrass and How Do I Get Rid of It?

There was a fair amount of quackgrass on the farm where I worked as a teen. In town, however, crabgrass was a more common problem — and one that was easier to solve since it spread by seed only and not aggressive underground runners. Quackgrass was a different story. Despite its whimsical name, quackgrass is a formidable enemy that can quickly run roughshod over a lawn.

Quackgrass’s strong, deep root system gives it staying power, and when split into pieces, that same root system sprouts easily into new plants, ensuring it won’t go away without a fight. Moreover, there isn’t a selective herbicide that kills quackgrass without hurting any surrounding turf. That’s why quackgrass — also known as couchgrass, quickgrass, quitch, scotch, twitch, dog grass and witchgrass — is one of the hardest weeds to eradicate.

Read on to learn how to identify and eliminate this aggressive invader.

What is Quackgrass?

Quackgrass (Elymus repens) is a perennial, cool-season grassy weed that lives primarily in northern latitudes. This invasive weed is easily identified by its broad, rough leaves, which usually stand taller than surrounding turfgrasses. “It has a higher vertical expansion rate, so it grows faster than other grasses,” says Jon Trappe, turfgrass extension educator for the University of Minnesota. That means it sticks out only days after mowing and can reach 3 to 4 ft. tall if left unmowed.

Identifying Quackgrass

Quackgrass resembles crabgrass but can be identified by its upright structure and clasping auricle, a claw-like appendage that wraps around the stem at the base of the leaf. It also has rhizomes with sharp points reaching up to 11 ft. long. These underground runners allow the plant to spread quickly. Quackgrass has a few other advantages in the fight for dominance. “It’s more drought tolerant than many grass species,” Trappe says, “and it is suspected to have some allelopathic properties.” Allelopathic plants release chemicals from their roots to stunt the growth of nearby plants. He explained that this is actually more common in nature than originally thought, yet it can be hard to confirm in individual species.

How Does it Spread?

Quackgrass generally spreads through rhizomes, the plant’s underground runners. It can also spread by seed. According to Oregon State University, each quackgrass plant produces a few dozen seeds, which can stay viable in the soil for one to six years.

How to Kill Quackgrass

Here are some methods to control or eradicate this pesky weed.

• Remove it by hand. If quackgrass has yet to establish itself in the lawn firmly, you can try removing it by hand. Moisten the soil and use a hand tool to remove young quackgrass plants growing individually or in small patches. Be sure to remove all root fragments because any left in the ground will resprout into new plants. If this happens, remove the regenerated plants before they have more than four leaves. According to the University of Vermont Extension, repeating this several times will eventually kill the stand.

• Turn up the Heat. You may be able to contain it through solarization, which bakes the soil. Fasten clear plastic sheets over the quackgrass area and leave them in place for five to seven days in summer. The plastic traps the heat close to the soil surface to kill the plant. “I have seen very mixed results with that. It is not completely effective for controlling quackgrass and can take several weeks in the middle of summer, but it does not kill all the rhizomes,” Trappe says. “It’s just really killing the aboveground portion. I would not recommend solarization unless you are following up with herbicide.”

• Treat it with Herbicide. One of the most effective control strategies is to apply a non-selective herbicide containing glyphosate when plants are young, green, actively growing and not stressed by drought. “You can kill it off in one application, but a lot of times you need to wait weeks for it to resprout from the rhizomes so you can get a good kill” with a second application, he says. “You just have to be patient.” The problem is that non-selective herbicides will damage or kill all living plant tissue that it touches. One strategy is to use a paintbrush to apply herbicide to the leaf surface of quackgrass, which is easy to visually isolate due to its height and gray-green color. Wear gloves to limit your exposure to the herbicide.

• Make it Disappear. Some have had success making existing quackgrass “disappear” into the turf. This is done by mowing more frequently and also fertilizing the lawn regularly with a nitrogen fertilizer to increase the vigor of surrounding turfgrasses and effectively choke out quackgrass. This won’t kill it entirely, but what remains will be darker green in color because of the increased nitrogen and therefore blend in better with other grasses. “You can help maintain a dense turf by following best turf management practices,” Trappe says. “Unless it’s something that is really important from an aesthetic standpoint, I don’t think they need to deal with it.”

Sod or Seed?

If an area of your lawn becomes badly infested, you may need to treat it and then replant the entire area with sod or seed. Sod has the advantage of smothering any new growth that might originate from remaining root fragments in the soil. But it is more expensive than seed and offers limited turfgrass options. “I’m a big fan of seeding,” Trappe says. “It gives you more flexibility and more options for cultivars or grass mixtures.”

About Our Expert

Jon Trappe is Extension Educator for the University of Minnesota, working with homeowners, master gardeners and turfgrass professionals to answer questions and furnish information on turfgrass management. He received his B.Sc. in Agronomy from Purdue University and M.Sc. in Horticulture from the University of Arkansas. After receiving a Ph.D. at Purdue University, Jon came to the University of Minnesota as a postdoc and focused among other things on projects related to weed suppression in fine fescues. He also played a role in the development of outreach programming, including helping launch an online course focused on roadside turfgrass installation and management.

Sources

• University of Minnesota Extension: “Quackgrass”
• The University of Vermont Extension: “Quackgrass Management”
• Turfgrass Science at Purdue University: “Quackgrass”
• University of Minnesota Extension: “Quackgrass Control in Turf”