How Do You Kill Quackgrass Without Killing Grass?

How Do You Kill Quackgrass without Killing Grass

Quack grass is also known as common couch grass and can be a bane to many lawn owners who have issues with warm-season weeds. A patch of this grassy weed can choke out desirable grass, pop up in flower beds, and even take over the entire lawn. An invasive weed with upright grass blades that spreads by underground stems and rhizomes, quack grass is a worthy adversary for sure. 

I remember my first encounter with this particular grass weed, I was spreading grass seed on a warm season lawn in a transitional climate that had died from overshading. I spread some tall fescue seeds to mix and help in the shade, but that’s not what grew. By the time I was able to cut the turf, it was at least 60% quack grass and spreading. The info below is what I did about it.

How to Remove Quack Grass and Protect Lawn Turf

While a quack grass infestation can best be prevented before it even happens, in my situation, it was too late. I hadn’t even seen any quack grass prior, so when I prepared the soil and sowed the seeds, I didn’t think to spread a pre-emergent herbicide for the quackgrass plant.

Quackgrass

I know better now, but with these turf weeds encroaching on my lawn, I needed to look at all my options. I preferred a non-chemical approach and wasn’t in a hurry to redo the lawn, but in some cases, the right selective weed killers or post-emergent herbicide could have solved my problems. 

Over Seed Turf

One way to beat almost any stubborn weed is to plant way more seeds than you need, like your would in gardens. Make sure to try and coordinate sowing the seeds with the rain so you can have the greatest success. Cover the grass seed with a plastic net or anything to keep birds and pests from eating your freshly planted grass. 

To fill in your landscape and crowd out weeds with healthy plants, you will want to sow the seeds densely. A good amount is 2 lbs per 1000 sqft. depending on the turf type and the size of the grass seed. Filling in areas of bare or weak turf with lawn-type grasses will limit the growth of quackgrass but cannot kill the existing plants. Water and give fertilizer to the new grass and avoid foot traffic until the roots are established.

Adjust Lawn Routine

A well-maintained lawn has a way lower chance of being affected by weeds like quack grass than one that is inconsistently watered and mowed. Giving your lawn the right fertilizer and enough water, especially during the summer heat, is the only way to keep invasive summer weeds from popping up. Once they are established, it can be a lot of work to get them all out. 

In most climates watering at least an inch of water once a week can keep turf grass vibrant and green. Sometimes, thirsty turfs may need more water than that when it is exceptionally hot and dry.  If you have a lawn type that goes dormant in the summer, then reduce your watering to the correct rate or you may overwater and promote aggressive weed growth. 

Mowing can also be used to curb the growth and spread of a tenacious weed like quack grass. While it will not kill the grass, it can prevent seed heads from forming and increase the effects of non-selective herbicides like round-up. It is usually enough to mow anytime the turf grows taller than 3 inches but never mow more than 1/3 of the grass blade length at one time, or it may shock the plant.

Add Slow Release Fertilizer

A great lawn care program will always include a healthy fertilizer regime. To avoid a complete lawn takeover by nasty weeds like quack grass and to prevent crabgrass in lawns, the right fertilizer is needed. Often the hardest turf weed to kill with chemicals can be eliminated by helping make sure your lawn flourishes.  

Feeding your lawn high nitrogen fertilizer during active growth periods will give your turf grass a boost that can help it outgrow weeds. Using fast-release nitrogen fertilizer when quack grass is already growing can backfire and feed the weed instead. A healthy turf built over time on good soil is the key to defeating weeds like quack grass for good. 

Precise Spot Treatment

Non-Selective, foliar-absorbed herbicides can kill quackgrass but will harm the surrounding turf if not accurate. A common glyphosate herbicide like roundup will kill grass plants but is not discriminate and will harm turf and weeds the same. All-purpose herbicides must be applied precisely to avoid killing lawn grass.

 If your lawn is just beginning to get quack grass or the areas are isolated from other sections of lawn grass, you can use grass-killing herbicides. Very little of the chemical is transferred to the soil if no direct contact with herbicides like roundup is made, so make sure to spray very carefully.  Once the grass is dead, the poison will not spread, but you cannot party when it is windy. Herbicide applied in full sun, just after mowing, will work the fastest. 

Manual Extraction

Eliminating invasive plants without grass-killing herbicides can be difficult but is possible. Quack grass can be dug up or pulled out, but care must be taken to not break the rhizomes, or they will resprout. To achieve this, you will need to dig or remove a large area around the roots of the weeds and lift it all out carefully.

If you will be pulling, it is best done on young quack grass with shallow roots and attempted only when the soil is wet or damp. 

After the quack grass is removed, you will need to carefully dispose of it so that it will not reinfest your yard or garden beds. While digging up the weeds, you may have removed some desirable turf, this can be replaced after the quack grass roots have been detached. Amend the damaged soil with compost and plant new turf seed to make sure quack grass doesn’t come back. 

Solarization

Using the heat of the sun while blocking the light of the sun is an effective all-natural way to kill weeds. An anchored-down plastic sheet is often the preferred method of polarization used for weed extermination. A white plastic tarp over the weeds will weaken and kill the problem grass while sparing the other turf and soil microbes from chemicals. 

To treat sections of the lawn, you can cut black plastic into small pieces. As the sun heats up the ground and soil weed seeds, the grass blades and the entire root ball of invasive plants are killed.  Ideally, you will leave dark plastic for 6 weeks in summer and longer in cool shady conditions. Colored plastic or white plastic can also be used with different ambient heat results, but the main goal is to give the tarp lots of time to work and kill invasive weeds. 

How to Recognize Quack Grass?

Quackgrass

Quack grass is a very common weed in warm-season lawns and can be found spreading where turf grasses are weak or neglected. If given a chance to take hold, this weed will spread and grow and can be hard to tell apart from several other turf weeds when young. By the time you know it’s quack grass, it will be established and much harder to remove. 

Signs to look for with this weed, like the hairy lower half of the stem and smooth upper half, can help you identify and kill it before it becomes a real nuisance. check out these signs of quack grass on your lawn.

SignWhere to LookWhat It Means
Green-Blue ColoringLeavesIt’s not crabgrass
Broad LeavesLeavesIts warm-season weed
Hollow StemStemVulnerable to non-selective herbicides
Active Growth in Cool WeatherWhole grassCan grow in most climates
Stalky Upright Growth HabitStemIt’s not crabgrass
Dense GrowthWhole grassIt’s a warm-season weed
Clasping AuricleLeaf blade around the stemIt isn’t crabgrass or fescue

Appearance

The main weed that quack grass will be mistaken as early on is crabgrass. There are some herbicide methods that will kill crabgrass that may not be as effective on quack grass. Look for a green-blue coloring on the broad leaves of that weed. The hollow stem can be seen from above after cutting and is an indicator that this weed can sustain itself in hot, dry conditions once deep roots are set.

Growth Habit

Warm-season turf grasses start to go dormant in the cool winter, but quack grass can often use this time to grow dense patches that are hard to remove. Unlike crabgrass that sprawls prostate, quack grass grows upright and tall. The leaf blade curls around the stem of this grass as it grows in what is called a clasping auricle. These signs can help confirm you have quack grass to kill while there is still time to do it. 

Will Vinegar Kill Quack Grass and Lawn Grass?

Vinegar is often hailed as a quick weed killer, like boiling water and salt. While these all work, they may not be the best for your yard as everything tends to be affected by these methods. If you want to try a natural weed killer, then mixing the right concentration of vinegar will make it more effective. 

Vinegar kills all plants in the area and can stun or kill some soil organisms. Most of the time, one vinegar treatment is not enough, and reapplication is needed. This can further harm grass and make it tough for healthy turf to regrow. However, it is a better alternative to glyphosate if mixed correctly. 

A 10% vinegar solution is best to make sure you will be starting with a suitably acidic chemical. Add to water at a concentration of 20%. Hot or boiling water will do even more damage to stubborn weeds. You can add orange oil or other natural herbicides to increase efficiency and possibly prevent resprouting and healing of the surrounding weeds.

Combine the vinegar treatment with other methods of removal like plastic or manual extraction for faster results. Compost the area and resow after quackgrass is gone and resprouts have been eliminated to give new grass a better chance of no competition growing.

Is It Possible to Eliminate Quack Grass and Not Turf Grass?

Quackgrass

There is no immediate solution to quack grass removal that won’t harm neighboring turfs. Any chemical and herbicide treatments will take several weeks to go into effect and will most likely harm the surrounding grass. Altogether this will slow the rehabilitation of your lawn and take more time than other common weed issues. 

Instead of trying to constantly fight and remove weeds, better lawn management techniques are recommended.  Several stages of weed removal are the best solutions for quack grass since a single approach is unlikely to give you the results you want. After the pesky weeds are removed, resowing and lawn care are needed to prevent reinfestation or other weed issues. Make sure you fix the lawn care problems that led to the quack grass infestation in the first place.