Best Weed Killer for St Augustine Grass (Top 10)

Are you looking for the best weed killer for St Augustine grass? You are at the right place, we tested multiple weed killers from different companies, and here are the top products for helping you make the right decision.

St Augustin grass is a warm-season turfgrass with a thick and relaxing feel and robust growth.

Since it is prone to weed, among other things, we need to prevent an invasion of weed before it wrecks your grass. 

Best Weed Killer for St Augustine Grass (Top 10 Picks):

Model

Usage

Result Visibility

Price

Roundup Ready-To-Use Weed & Grass Killer

Kills all types of weeds from the root

3 hours

Gordon's SpeedZone Lawn Weed Killer

Works for common and troublesome weed species

Within hours

Natural Armor Weed and Grass Killer

Effective for 250+ types of weeds

Within hours

Spectracide 96451 HG-96451 Weed & Grass Killer

Works for weeds on driveways, trees, flower beds, etc

3 hours

Southern Ag Atrazine St. Augustine Grass Weed Killer

Kills broadleaf weeds

3 weeks

Scotts Liquid Turf Builder with Plus 2 Weed Control

Kills chickweed, ground ivy, henbit, among other weeds

24 hours

Ortho WeedClear Lawn Weed Killer Ready to Spray

Kills all main broadleaf weeds

A few weeks

Hi-Yield Atrazine Weed Killer

Kills Burweed

-

Scotts WeedEx Southern - 4,000 sq. ft., Weed Control

Works on southern grasses, including st Augustin grass, centipede grass, and carpet grass

3 weeks

Ortho 0430005 B Gon Weed Killer for Lawns

Kills weeds to the root

Within hours

1. Roundup Ready-To-Use Weed & Grass Killer

Roundup has been in the production of herbicides for long enough to be trusted. Their weed killer is one of the best out there:

  • Shows result in 3 hours
  • It kills all types of weeds from the root
  • Replacement policy
  • No-mix formula
  • Rainproof in 10 minutes
  • You can use it around vegetables, mulched beds, patios, etc.
  • Pump n go style.

This liquid kills the plants effectively enough. I had to take out a whole section of overzealous weeds in a raised bed, and it took two rounds of spraying a day, and it killed all the weeds! There were too many to pull up, so this was convenient.

The application of this weed killer is smooth and easy. Since the spray is battery operated and batteries are provided with the spray, it makes the whole process much quicker and hassle-free. Since it is ready to use, I could use it right out of the box. 

Also, this spray is super fast. After you have sprayed it on the weeds, you will see them die down within a day.

I have noticed that it does its job even faster when spread on a hot, dry day. I suggest keeping it away from the grass you don’t want dead.

However, one problem with this was that the tubing was kinked from inside the handle, and I had to pull the white tubing out enough to lessen the kink.

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2. Gordon’s SpeedZone Lawn Weed Killer

  • Visible results within hours
  • It Covers 14000 to 18000 square feet
  • Works for common and troublesome weed species
  • Cool-weather performance

The best part about this weed killer is that it targets all kinds of common and rare weeds.

It gets them to all and that too, quickly. I tried applying other herbicides, but some weeds were always left behind, but not with this one.

Also, this formula solved the issue of an infestation of sticker burs that plagued us.

They were all over the house, and were too many to pull out, but this weeds killer got rid of them as well. 

Moreover, this weeds killer gets the job done without harming your grass!

This year, I had creeping Charlie, clovers, and wild violets in my yard, and after two applications, I was pleased to find that the weed was gone, but my grass was still the same.

However, one issue with it is that although it works effectively, sometimes it takes weeks to show accurate results, so you need to stay patient.

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3. Natural Armor Weed and Grass Killer

This natural armor weed killer is one of its kind. The all-natural concentrated formula is highly in demand and for all the right reasons. Let’s see its features:

  • Contains no glyphosate
  • Effective for 250+ types of weeds
  • No mixing or diluting required
  • It can be used at all places where vegetation is not needed
  • Fast results
  • 30-days money-back guarantee

I am troubled with a hefty smell that comes after the weed killer is applied, but this weed killer had a pleasant after-smell that didn’t get too much into my head. Thus, it made the application a bit breezy.

Also, I lived in a desert community, and we recently had a lot of rain, thus creating a weed problem.

Some weeds were more troublesome than others, and I did not expect them to be gone so soon, but within hours, they vanished! 

Moreover, my item was well packaged. With other sprays, I noticed that there were mostly some leakages when they were delivered, but this one was appropriately packed, and I could use it immediately. 

However, note that the after-sale service is not up to the mark. I called them twice regarding an issue, and they took a week to get back to me.

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4. Spectracide 96451 HG-96451 Weed & Grass Killer

  • Volume is 64 fluid ounces 
  • Results visible in 3 hours
  • It kills the weed from the root
  • Works for weeds on driveways, trees, flower beds, etc
  • Mix and apply with a tank sprayer
  • Money=back guarantee

I used 7 ounces per gallon of water, waited 24 hours to see the weed die, and it will take up to 2 days for the weed to properly pass. It works slower in shady areas, so that it might take extra days in such areas. The results do start to show!

I have successfully killed the toughest weeds, including buttonweed, goosegrass, and spotted spurge.

It would help if you spotted spray these weeds as this weed killer will kill anything it touches, and you don’t want your entire yard ruined.

Moreover, as someone who lives in an area that receives heavy and regular rainfall, this product becomes more suitable.

It becomes rainproof in just 15 minutes, so I don’t have to wait for a sunny and dry day to apply it.

One trouble that I faced with this product is that the instructions are a bit misleading and confusing. However, the product works just fine.

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5. Southern Ag Atrazine St. Augustine Grass Weed Killer

  • Kills broadleaf weeds
  • You can use it in centipede grass
  • Provides suppression of grass
  • Controls weed from seeds and emerged weeds

Earlier this year, I noticed that crabgrass was taking over my St Augustin grass, and I found out that atrazine worked well with controlling crabgrass weed. Just know that atrazine is more effective in the spring and fall seasons.

One thing to be noted is that this weed killer takes a while to show results, so you have to remain patient.

I was getting worried after a week, but after three weeks, the weed did die down and made a significant improvement in my grass.

I used 5 ounces of surfactant and two-quarters of atrazine mixed into 5 gallons of water and applied it to approximately 7500 square feet. It worked well, and I could apply it in a short period.

One slight problem with the product is that it is more expensive than the rest, but the results make it worth it.

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6. Scotts Liquid Turf Builder with Plus 2 Weed Control

Scotts is a brand known for yard products and taking care of your garden needs. Following are the main characteristics of the product:

  • Volume is 32 oz
  • Shows result in 24 hours
  • It kills chickweed, ground ivy, henbit, among other weeds
  • Attach hose and spray
  • Don’t spray on flower beds, around trees or shrubs
  • Spray when weeds are actively growing

The key to effectively using this product is to water your lawn 20 minutes before spraying this weed killer. If you follow these directions, you’ll notice that it kills almost all weeds and keeps the grass green and healthy.

Also, after application, I noticed that it only killed the weeds and not the healthy grass, which is a great plus. There is mostly a spillover of the product on healthy grass, and they get destroyed in the process.

It not only targets weed only, but it accelerates the growth of the grass too, that too quickly! Also, since it is a spray, it is highly convenient to use; just keep an eye out on the liquid level and follow instructions.

One drawback of this product is that the bottle sometimes does not spray well and gets stuck. However, the product is not faulty.

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7. Ortho WeedClear Lawn Weed Killer Ready to Spray

  • Volume is 32 fluid ounces
  • Kills all main broadleaf weeds, including dandelion and chickweed
  • Deliver results in hours
  • Rainproof within an hour
  • Suitable for multiple types of laws, including bermudagrass, tall fescue, etc.
  • Treats up to 5000 square feet

The battery-powered sprayer it comes with makes life a lot easier. You can just grab the bottle and walk around the lawn to spot-treat the tough weeds without having to mix and pump a sprayer.

I lost most of my lawn to weeds after going organic for a couple of years.

Since it is a contract killer, most of my grass was intact even after I had sprayed them with it. This weed killer took some weeks, but the weed died.

Also, I would like to suggest adding some surfactant solution to the product as it helps the liquid stick on the weed, rather than running off them like water. I believe it quickened the process of weed dying.

However, one issue I faced was that it does not work well on dandelions, so you might want to reconsider if you plan to use it for that.

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8. Hi-Yield Atrazine Weed Killer

Atrazine’s weed killer has excellent reviews, to begin with, and is a lasting product. Listed below are some of its features:

  • Volume is 32 fluid ounces
  • Made in china
  • Concentrated

Where I live, there is a specific type of weed called burweed that grows unnoticeably and is like carpet grass, so it doesn’t grow too much.

The problem is that you can’t catch it in the initial stages. I could kill all of it with this weed killer when I did. It did a fantastic job!

It not only kills the existing weed but also prevents new weed from growing! I roamed around my lawn months after applying this product, and there was no sign of burweed anywhere.

One important tip is to follow the instructions word by word! It is only to be used twice a year, the temperature has to be greater than 90F, and the lawn has to be watered three days after applying the product. 

One issue that I noticed is that it sometimes kills some of the grass when there is a significant spillover.

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9. Scotts WeedEx Southern – 4,000 sq. ft., Weed Control

  • Suitable for southern grasses, including st Augustin grass, centipede grass, and carpet grass
  • Works in all seasons
  • Watering immediately post-application
  • It covers 4000 square feet

I put it on my st Augustin grass three weeks ago and finally saw the difference. The weeds are disappearing, and the grass is getting darker in the shade of green. When the rain stops, I’ll cut it out.

Also, the product is not very heavy on the pocket. The price is not unreasonable with the amount of area this bottle covers.

Since the price was competitive, I ordered two bottles and am still using them.

Moreover, the fact that it works in all seasons makes it all the more convenient.

Some weed killers are only suitable in certain weather conditions, but you can use this one at any time of the year.

However, the issue is that it does not work as well on bermudagrass as it does on st Augustin, and this is not mentioned on the product.

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10. Ortho 0430005 B Gon Weed Killer for Lawns

  • Volume is 128 fluid ounces
  • It kills all kinds of broadleaf weeds
  • Effective on 250+ types of weeds
  • Results visible within hours

I had patchy yellow grass for over months, and I finally decided to remove all the weeds and make my yard beautiful again.

Considering the cost of this weed killer, I’d consider it a wise move to use this as. Eventually, all the weed disappeared.

Also, this is the kind of weed killer that leads to a slow but sure death of weeds compared to an instant one. It does not kill them right away but kills every weed present in your grass.

Moreover, this product is excellent for significant areas. I had a 1-acre lawn, and to maintain that, I always struggled.

This product took care of everything; It not only killed weeds but prevented the emergence of new ones as well.

However, you should note that it is not recommended for chickweed as it is not as effective on them as on other kinds of weeds.

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Factors to consider before buying:

  • It is crucial to see that the product you use only kills the weed and not your grass, defeating the entire purpose. Herbicides, for example, will not kill your grass.
  • Type of weed: before you purchase the weed killer, inspect your garden, and try to find out the kind of weed you have since different products specialize in various types of weeds.
  • Coverage: some weed killers are diluted and won’t cover a large area, so it is highly recommended that you consider the size of the site you wish to use your product. Concentrated weed killers cover larger areas relatively. 

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