Oh No, My Lawn Looks Worse After Roundup! How to Fix Grass Killed by Roundup

Many homeowners apply Roundup to their lawns, only to have the panic of discovering later that the lawn looks even worse than it did before. Roundup produces several products that contain herbicides that work on different broadleaf weeds as well as multiple varieties of grasses. Sometimes homeowners choose the wrong type of Roundup for their gardening.

How to fix grass killed by Roundup | Dead lawn.

It is possible to fix grass killed by Roundup by reseeding. Roundup Weed and Grass Killer is a non-selective glyphosate herbicide that kills broadleaf plants and grasses. Roundup For Lawns is made from herbicides that kill weeds but not most grasses. Bermuda grass may turn yellow but will recover.

When attempting to kill weeds in your lawn, it is vital that you choose the correct Roundup product. Choosing the wrong product will result in a dead lawn – woops!

Sometimes a homeowner actually uses the right weed killer for their lawn, but then the lawn dies, and they discover that what they thought was grass turned out to be mostly weeds and crabgrass.

Today we will explore exactly what product to use, and how to fix grass killed by Roundup.

Our first step is to understand the difference between Roundup Weed and Grass Killer vs. Roundup for Lawns.

Roundup Weed and Grass Killer

This Roundup product is made specifically to kill all grass and weeds in a specific area.

Roundup Ready-to-Use Weed & Grass Killer III - with Pump 'N Go 2 Sprayer, Use in & Around Vegetable Gardens, Tree Rings, Flower Beds, Patios & More, Kills to The Root, 1.33 gal.
  • Kills the toughest weeds and grasses to the root. Guaranteed (Consumer Guarantee: If for any reason you are not satisfied after using this product, simply send us original proof of purchase and we will refund the purchase price.)

It is a glyphosate-based herbicide that is non-selective. When caring for your lawn it’s important to understand that anything that gets this glyphosate spray on it will die.

Sometimes homeowners mistakenly use this type of herbicide thinking that it will kill only the weeds in their lawn, without realizing it will also kill the grass.

  • Roundup Weed and Grass Killer can be used to kill any unwanted weeds and grasses in any area. This is a favorite product for keeping sidewalk cracks, driveway edges, and rock paths clear of weeds and creeping grasses.
  • This product can be used to spot-spray weeds in vegetable and flower gardens. Apply it to the unwanted plants until all leaf surfaces are wetted with the product. Overspray or unintentionally applied Roundup can be immediately rinsed off of plants and they will be fine.
  • Roundup Weed and Grass Killer can be applied before rain as long as it has had 10 minutes to settle in. This means that homeowners can apply this product with less worry about it washing onto wanted plants and causing unintentional damage.
  • This product should never be used to control weeds that are growing in the lawn. It will kill the surrounding grasses as well.
  • Homeowners who apply this product to the lawn will kill the lawn. The lawn will need to be reseeded.

The basic rule of thumb for using Roundup Weed and Grass Killer is that you should not spray it on anything unless you want it to die.

Weeds and grasses that are treated with glyphosate will die down to the root. Replanting can occur right away, depending on what you are going to plant in the area. We will go over those details later in this article.

Roundup For Lawns

Roundup For Lawns is a mix of selective herbicides that kills broadleaf weeds and keeps turfgrasses looking healthy.

It will kill dandelions, crabgrass, clovers, foxtail grasses, and every other invasive nuisance while keeping turf grasses such as bluegrass, fescues, and ryegrasses looking green and healthy.

  • Lawns that are mostly clovers, crabgrass, dandelions, and other invasive species will die from application of Roundup For Lawns. This is the perfect opportunity for the homeowner to start over and reseed the lawn.
  • Lawns that are planted with bermudagrass may turn yellow. However, the lawn will recover with time and watering. Bermudagrass can not tolerate Roundup For Lawns if it is applied in temperatures over 85 degrees Fahrenheit (29.44 degree Celsius). 
  • Roundup states in the product information that Roundup For Lawns will kill grasses such as bent grass, St. Augustine, bahia grass, Centipede grass, and carpet grass. Lawns that are made of these varieties of grasses will be killed with the application of this product. 
  • Homeowners who do not know what type of grass they have in their lawn can consult their local extension office or try a grass identification guide such as this one from the Roundup website.

Another thing to keep in mind when applying an herbicide to the lawn is to avoid doing this during vulnerable times of the year. Do not apply herbicides when the lawn is recovering from other procedures such as aeration. A lawn that has recently been plugged will be in an active recovery phase. It will not tolerate an herbicide as readily as an established lawn.

Also, do not apply these herbicides to recently sodded or planted lawns. Give the lawn a good three-inches of growth, roughly six weeks after seeding, before applying any kind of herbicide. Then, be careful to purchase and apply the correct type of Roundup.

How To Fix a Grass Killed By Roundup

As you can see, it’s quite easy to make a mistake and accidentally use the wrong type of Roundup on your lawn.

Thankfully, both formulas are very forgiving when it comes to replanting in the area.

The only formulation of Roundup that will require a long recovery time after application is Roundup Extended Control Weed and Grass Killer Plus Weed Preventer. This product kills all grasses and weeds in an area and will not allow germination in the soil for at least the next four months.

Homeowners often panic after treating the lawn with Roundup, thinking that they have made an irreversible mistake by applying the herbicide. However, these brown patches are a blessing in disguise. They make a perfect opportunity to overseed the grass and begin nurturing a lawn that will be much more enjoyable in the long run.

Overseed for Roundup Repair

Overseeding is the process of applying a fresh layer of grass seed on an existing lawn to refresh the turf.

This is a great way to reinvigorate an existing lawn without starting over from scratch.

Overseeding will also fill in bare patches left behind from herbicide application. This method also helps to avoid the appearance of lush patches of reseeded grass in an otherwise tired lawn.

  • Begin by mowing the lawn. Normally the lawn should be mowed only one-third at a time, keeping the blades about three-inches tall. Before overseeding, the grass should be cut a bit lower to accommodate the new soil and seeds.
  • Aerate the lawn. This can be done with a plug aerator or a thatching rake. Both methods help to break up the top layer of soil and loosen up the thick layer of thatch that keeps nutrients from entering the soil to feed the grass roots.
  • Apply a quarter-inch layer of very fine mulch or high-quality soil. This should not be a layer of plain topsoil. The goal is to give the lawn a shot of high quality nutrients. Spread this mulch with a rake evenly across the entire lawn. The mulch should not be thick enough to kill existing grass. This is called topdressing.
  • A fertilizer can be applied over the top of the mulch. Some turf builder grass seed mixes have fertilizers pre-applied to the seeds so that homeowners can skip the step of fertilization.

When the new seeds come up, they will begin to blend in with the existing lawn, creating a new surface of turf.

This process can be repeated yearly, as the lawn begins to grow again. This method of topdressing the soil will help improve soil quality over time, and help to ensure that the grass stays healthy and thick enough to resist weedy invaders.


There are a few reasons why homeowners have a bad experience with Roundup.

The lawn may have been mostly weeds that are rightfully killed by the application of Roundup herbicides.

Secondly, the wrong product may have been broadcast on the lawn, causing the death of both weeds and grass.

In either case, it is possible to recover from a Roundup kill-off, and the process can begin right away.

Roundup is a forgiving herbicide that does not stay in the soil. Grass seeds can be replanted very soon, depending on the product that was used. The resulting lawn will look better than ever.

More Lawn Care Advice:

How to regrow grass after Roundup