How do you kill quackgrass without killing grass?

What is quackgrass?

Quackgrass is a creeping perennial grass weed that can be very invasive in home lawns, gardens, and agricultural fields. Its scientific name is Elymus repens. Quackgrass spreads rapidly through its aggressive rhizome root system and can quickly take over areas, crowding out desired plants and grasses. It’s considered a noxious weed in many areas. Quackgrass is quite difficult to control because any small pieces of root or rhizome left in the soil can re-sprout into new plants.

Why kill quackgrass?

There are several reasons why you may want or need to kill quackgrass:

• It crowds out desired lawn grasses, gardens plants, and agricultural crops.
• Its rapid growth can quickly dominate lawns and flower beds.
• It’s ability to regenerate from rhizome fragments makes it very hard to eradicate.
• It forms thick mats of stems and leaves that obstruct lawn mowers.
• Quackgrass harbors some viral diseases that can infect wheat crops.
• The sharp pointed seeds can injure mouths of grazing livestock.
• It produces chemicals that inhibit growth of other plants.

Quackgrass is considered an invasive weed in most situations, so killing it and limiting its spread is important for maintaining healthy lawns, gardens, and agricultural fields. Allowing quackgrass to thrive can quickly lead to monocultures of quackgrass that crowd out desired plants.

Challenges of killing quackgrass

Eliminating quackgrass is challenging for several reasons:

• It reproduces through seeds and an extensive underground rhizome (root) system that can penetrate lawn and field soils very deeply.
• Any small sections of quackgrass rhizome left in the soil after attempted removal can re-grow into new plants.
• Most weed control methods that kill the aboveground stems and leaves of quackgrass will not kill the underground rhizomes.
• Many herbicides that are effective on quackgrass can also kill or injure desirable lawn grasses and plants.
• Quackgrass is resistant to some types of commonly used herbicides.
• Its deep and extensive root system makes manual digging ineffective for complete removal.

These challenges mean quackgrass requires very persistent and thorough control methods to fully eradicate from an area. Often, multiple control techniques used together provide the best results.

How to kill quackgrass without killing other grasses

The keys to selectively removing quackgrass while sparing desirable surrounding plants are:

• Applying herbicides that target grasses but do not injure broadleaf plants.
• Spot treating quackgrass infestations rather than blanket applying herbicide.
• Using selective manual digging and removal of quackgrass plants.
• Repeated applications of control methods to kill regrowth from rhizomes.
• Encouraging healthy growth of desired plants to outcompete quackgrass.

Here are some recommended methods to achieve selective quackgrass control without harming other grasses and plants:

Selective Herbicides

• Glyphosate – This non-selective systemic herbicide will kill most plants including lawn grasses. However, if carefully spot sprayed only on quackgrass, it can be effective. Use a wand attachment on the sprayer to treat only quackgrass and avoid spraying desirable plants.
• Fluazifop – A selective grass killing herbicide labeled for use in many common cool season lawn grasses like bluegrass, fescue, and ryegrass. It will turn quackgrass yellow and kill it without injuring most surrounding lawn grasses.
• Sethoxydim – Another grass-selective herbicide that controls quackgrass but won’t harm other grass species. Can be used on lawns, golf courses, athletic fields.
• Clethodim – Used to control annual and perennial grass weeds in broadleaf crops, landscapes, and turf. Effective on quackgrass infesting areas of desirable plants.

Always check herbicide labels for listed use sites and specific application instructions. More than one treatment may be needed.

Manual Removal

• Use a spade or shovel to dig out quackgrass clumps. Try to sever rhizomes 4-6 inches below soil surface.
• Remove entire quackgrass plant along with roots and rhizomes – leave no fragments behind.
• Replace soil and reseed treated areas with desired grass species.
• May need to periodically spot treat regrowth.
• Can be labor intensive but avoids herbicide use.

Smothering

• Cover quackgrass infested areas with thick black plastic for a full growing season.
• Blocks light which kills quackgrass and most other plants under the plastic.
• Reapply plastic next season if rhizome regrowth occurs.
• Can use tarps, cardboard, or layers of newspaper instead of plastic.

Vigorous Grasses

• Maintain thick, vigorous stands of desirable grasses like tall fescue.
• Healthy grass crowds out space so quackgrass struggles to establish.
• Mow high and fertilize appropriately to encourage desired grasses.
• Overseed thin lawn areas vulnerable to quackgrass.

Solarization

• Cover quackgrass infested soil with clear plastic sheeting during hot sunny weather.
• The greenhouse effect solarizes the soil, heating it to temperatures that kill quackgrass.
• Can use clear poly tunnels, hoop houses, or cold frames to solarize soil.
• Needs full sun and at least 4-6 weeks of hot weather to be effective.

Vinegar

• Spray full strength vinegar directly onto quackgrass leaves.
• Works best on young, emerged plants less than 6 inches tall.
• Vinegar provides a non-selective burn down of vegetation, so avoid contacting desired plants.
• May take several applications. Vinegar does not translocate to the roots.

Salt

• Apply ordinary table salt or rock salt directly to quackgrass foliage and crowns.
• The salt desiccates and kills the plants over 1-2 weeks.
• Avoid heavy salt applications that can make soil incapable of supporting plant growth.
• Works best on young quackgrass plants under 6 inches tall.

What time of year is best for control?

Quackgrass control is most effective when attempted during these phases:

Spring

• Treat with glyphosate or systemic grass herbicides when quackgrass is 4-6 inches tall and actively growing.
• This ensures herbicide translocation down to the roots and rhizomes.
• Spring applications often require follow up treatments later in summer.

Fall

• Also a good time to directly spray foliage with glyphosate or grass herbicides.
• Cooler weather promotes herbicide absorption.
• Healthy desirable grasses are often going dormant, reducing risk of injury.
• Late fall applications may not take full effect until the next spring.

Summer

• Most challenging time due to weed stress from heat and drought.
• Herbicide effectiveness can be reduced.
• Risk of harm to desirable grasses is higher as they experience stress.
• Manual digging can be effective if soil is workable and all roots removed.

Conclusion

Quackgrass can be selectively removed from lawns and fields without killing desirable grasses, but doing so requires an integrated approach combining proper timing, selective herbicides, and thorough manual control methods. No single technique will completely eliminate quackgrass – it requires persistence over multiple seasons to fully eradicate. But with diligent effort and repeating control steps, it is possible to remove quackgrass while sparing desirable surrounding turfgrasses and plants. The keys are using selective systemic herbicides, thorough digging, proper timing of applications, and promoting vigorous growth of wanted vegetation.