6 Best Weed Killer for St Augustine Grass: Say Goodbye to Weeds

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Picture this – you’ve got this beautiful St. Augustine grass in your garden or lawn. But now those pesky weeds are trying to crash the party! Isn’t that irritating? However, let us assure you are not the only one facing a problem. Most garden enthusiasts have faced this issue!

So, if you want the weeds gone without messing with the turf that you have grown and maintained so carefully, there might be better ways than turning up the garden.

What’s the solution, then? A weed killer is your answer.

Spectracide Weed & Feed 20-0-0

Spectracide Weed & Feed 20-0-0

Our Top Recommendation for Weed Killers For St. Augustine Grass

  • Dual-action formula
  • Kills weeds
  • Quickflip sprayer
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To provide you with a solution to this issue, we’ve researched a lot, coupled with our own experience, to come up with the safest and most effective weed killers that’ll do the job without giving your St. Augustine grass a hard time.

Whether you are a seasoned gardener or just starting out, most weed killers we have suggested here are ready-to-use, so you can avoid the hassle of perfecting the measurements.

So, without further ado, let’s dive in.

6 Best Weed Killers for St. Augustine Grass

In this section of the article, we have mentioned the best weed killers for your St. Augustine grass, along with their pros and cons. This will undoubtedly help you make an informed decision about which one to go for.

Spectracide Weed & Feed 20-0-0 (Ready-to-Spray)Spectracide Weed & Feed 20-0-0 (Ready-to-Spray)• Dual-action formula
• Kills weeds
• Quickflip sprayer
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Scotts Turf BuilderScotts Turf Builder SummerGuard Lawn Food with Insect Control, Fertilizer and Insect Killer• Feeds and strengthens your lawn against heat and drought
• Can be used on any grass type
• Protects against listed bugs
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 Southern Ag Amine 2,4-D WEED KILLERSouthern Ag Amine 2,4-D WEED KILLER• Use in turf, pastures, rangeland
• Controls many broadleaf weeds
• Low, economical use
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Ortho Weed B-gon Chickweed, Clover & Oxalis Killer for Lawns ConcentrateOrtho Weed B-gon Chickweed, Clover & Oxalis Killer for Lawns Concentrate• Cannot be applied directly out of its container
• Apply this product to buffalograss, fescues
• Formulated to kill tough weeds in your lawn
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BioAdvanced All-In-One Lawn Weed and Crabgrass Killer I, ConcentrateBioAdvanced All-In-One Lawn Weed and Crabgrass Killer I, Concentrate• Smarttrack marker
• All-in-one formula
• Rainproof protection
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Preen Garden Weed PreventerPreen Garden Weed Preventer• Can be used after flowering plants
• Preen should not be used on flower seeds
• Prevent new weeds from sprouting
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1. Spectracide Weed & Feed 20-0-0 (Ready-to-Spray)

Spectracide Weed & Feed 20-0-0
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At number one on our list, we have Spectracide’s weed and feed dual-action formula to kill major broadleaf weeds while feeding your lawn. This fertilizer has a 20 percent nitrogen formulation, ensuring your lawn’s health is maintained.

This weed killer will help you control dandelions, chickweeds, knotweed, plantain, clover, mallow, purslane, and other broadleaf weeds.

It comes in a premixed, ready-to-spray bottle that you can easily connect with your hose and spray-no hassle of measuring and mixing. One spray bottle contains 32 ounces, covering up to 7,500 square feet of lawn.

Rating: It has an average online rating of 4.3 out of 5 on Amazon based on 8752 ratings.


  • Easy to use
  • Does what it claims
  • Best for broadleaf weeds


  • It can be a little pricey
  • Overusing can damage your turf
  • Might turn Bermuda grass brown
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2. Scotts Turf Builder SummerGuard Lawn Food with Insect Control, Fertilizer and Insect Killer

Scotts Turf Builder
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While we know that your focus is on weed killing, you might end up damaging the turf in the process. Therefore, before you start spraying weed killers, you can use Scotts Turf Builder to ensure that the St Augustine grass stays healthy.

On the plus side, this turf builder also works as an insecticide that controls lawn pests like ants, armyworms, chinchbugs, crickets, fleas, grasshoppers, spiders, and ticks. Apply this bug killer at the beginning of summertime when these lawn insects start showing their activities.

This product is suitable for any grass type, and one pack (40.05 lb) can cover up to 15,000 sq. ft. area.

Rating: It has an average online rating of 4.5 out of 5 on Amazon based on 6944 ratings.


  • Kills lawn insects that affect your lawn’s turf
  • Being a lawn food, it also provides necessary nutrients to your lawn
  • Shows results in no time


  • It comes in granule form; hence, you need to mix it carefully
  • Not following directions can lead to scattered burn spots
  • It will not help you clear weeds
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3. Southern Ag Amine 2,4-D WEED KILLER

 Southern Ag Amine 2,4-D WEED KILLER
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If you are looking for a commercial-grade product, this is the one. It’s a highly potent herbicide that kills a variety of broadleaf weeds and works on woody vines, shrubs, and smaller trees. Therefore, if your lawn is under attack from poison ivy, this will do the job.

This highly concentrated herbicide will help eliminate some of the most invasive and stubborn weeds and plants without damaging your grass. So you can use this for turf, pastures, rangeland, ditch banks, and fences.

It is a silver amine-based liquid, and only 2 to 3 tablespoons of product is required in 3 to 5 gallons of water, and it can cover 100 sq ft of area. Therefore, a little goes a very long way.

Rating: It has an average online rating of 4.4 out of 5 on Amazon based on 6243 ratings.


  • Highly potent
  • Kills broadleaf weeds and other woody invasive plants
  • Requires very little quantity
  • It can be used for professional purposes


  • Not recommended for beginners
  • It would help if you were very cautious with the directions, or it can also damage the grass.
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4. Ortho Weed B-gon Chickweed, Clover & Oxalis Killer for Lawns Concentrate

Ortho Weed B-gon Chickweed, Clover & Oxalis Killer for Lawns Concentrate
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Ortho’s Weed B Gon is another good broadleaf weed killer that targets weeds like Clover, Oxalis, ground ivy, Speedwell, wild violet, and Chickweed. You need to dilute and spray a Triclopyr and Triethylamine salt-based formula.

It is claimed to be rainproof for up to 6 hours, and the manufacturers suggest using it during the active growth period of the weeds, which is usually when the temperatures are below 90 ℉. The product comes in a 16 fl oz size, treating up to 3200 sq ft area.

However, they have also launched a ready-to–spray variety that you can check out if you are not confident about getting the measurements right. You can connect it directly to a garden hose or tank sprayer or purchase their Ortho Dial N Spray.

However, we must mention that this product is not the quickest when it comes to producing results. Most people see good results after two courses of spray every two weeks. Hence, you can skip this if you want something that can give you immediate results.

Rating: It has an average online rating of 4.2 out of 5 on Amazon based on 5832 ratings


  • Beginners friendly.
  • Rainproof for up to 6 hours.
  • It comes in two varieties; one is ready-to-spray. 


  • It falls under more enduring and time-consuming weed killers.
  • Spraying too much too soon can burn your grass.
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5. BioAdvanced All-In-One Lawn Weed and Crabgrass Killer I, Concentrate

BioAdvanced All-In-One Lawn Weed and Crabgrass Killer I, Concentrate
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BioAdvanced’s all-in-one weedkiller claims to kill over 200 lawn weeds and crabgrass species without harming the grass.

Its “Smart-track non-staining” red marker helps you distinguish the areas you have already sprayed to avoid overlapping and over-spraying. But don’t worry, you won’t be left with red-stained grass, as the stain wears off with sunlight. The formula is also rainproof for up to 1 hour so that you can get away with a little cloudburst.

Although they mention that the product suits Bermudagrass, Buffalograss, Kentucky Bluegrass, Ryegrass, Fescue, Zoysia, and Bentgrass, people can use it for St. Augustine.

Rating: It has an average online rating of 4.1 out of 5 on Amazon based on 4311 ratings


  • Kills over 200 species of crabgrass and weeds
  • Has a smart marking formula that helps avoid overlapping
  • Provides rain protection for 1 hour


  • Takes time to show results
  • You might need to check the recommended dosage for certain weed types, like clovers.
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6. Preen Garden Weed Preventer

Preen Garden Weed Preventer
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If you have already applied a weed killer once and got results but now want to maintain it, try using this weed preventer by Preen. Instead of killing the weeds, it prevents them from growing and budding. Therefore, it is significantly less harsh than other weed killers discussed earlier.

It can help stop weed from growing for up to three months, so you might not need to spray those powerful weedkillers that often. It also ensures that the weed roots that dodged the weed killer and can’t be seen on the surface level don’t sprout and stay dormant. Unlike other weed killers, you can apply it anytime throughout the year.

Rating: It has an average online rating of 4.5 out of 5 on Amazon based on 1059 ratings


  • Easy to use
  • Does what it claims
  • Best for broadleaf weeds


  • It can be a little pricey
  • Overusing can damage your turf
  • Might turn Bermuda grass brown
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Things to Keep in Mind Before Spraying Weed Killers

Things To Keep In Mind Before Spraying Weed Killers

You must be very careful with herbicide applications, or they might harm your turf instead of killing the unwanted weeds.

So here are some things you should be mindful of before picking and applying weedkillers on your lawn.

1. Pick the Right Product

To pick the correct type of herbicide, you must have knowledge of the plants in your garden. Identify the plants you want to save and the weeds you want to kill and pick herbicides that will only kill the weeds without harming the plants in any way.

If you choose the wrong one, it can have an adverse reaction on your grass and might also stun the growth of your other plants.

2. Thoroughly Follow the Instructions

Thoroughly follow the instructions

It is almost a law that you MUST follow the instructions line by line. Failing to do so might stop you from getting the desired results and can also affect the turf.

3. Water Your Lawn Before Spritzing the Herbicide

A thin layer of moisture before spraying the weed killer ensures the product would stick better to the weeds. You can’t water your lawn for quite some time after spraying the herbicide, or it can get washed off. So, it’s better to water your lawn beforehand.

4. Avoid Spraying in Harsh Sunlight

Avoid spraying in harsh sunlight

Spraying herbicide in broad daylight can cause it to evaporate quickly. Some herbicide formulas (especially granular ones) require water for activation. Thus, they might not work under harsh sunlight.

5. Maintain Safety Precautions

Herbicides are harmful to plants and equally dangerous to humans and other animals. So, if you have pets and children at home, keep them away from the lawn for 24-72 hours after spraying herbicide.

Also, remember to wash the sprayer thoroughly before storing it. Keep the herbicide in a sturdy, airtight container. While spraying, wear gloves and a gas mask to avoid direct contact and inhalation.

What are Some Common Weeds Found on Your St. Augustine Lawn?

What Are Some Common Weeds Found On Your St. Augustine Lawn?

If you are having difficulties identifying the type of weed that infiltrated your St. Augustine grass, then we have listed here some common weeds that grow alongside it.

  • Dollarweed (Pennywort): Recognizable by its round leaves resembling small lily pads, dollarweed thrives in moist areas and can be a nuisance in St. Augustine lawns.
  • Clover: Clover leaves typically have three leaflets and can thrive in lawns with nitrogen deficiencies. It’s easily recognizable due to its distinctive leaf shape and tiny white or pink flowers.
  • Crabgrass: This grassy weed is known for its fast growth and can easily invade bare or thin areas of a St. Augustine lawn, especially in warmer months.
  • Dandelion: Dandelions are easily recognizable by their yellow flowers that transform into fluffy seed heads. They can spread quickly and are often found in lawns with nutrient imbalances.
  • Wild Violet: With heart-shaped leaves and purple or blue flowers, wild violets can be tough to control in St. Augustine lawns, especially in shaded areas.
  • Spurge: Spurge weeds have a prostrate growth habit and can form dense mats. They produce small, inconspicuous flowers and can be a challenge to manage.
  • Nutsedge: Also known as nutgrass, this weed has triangular stems and can grow faster than the surrounding grass, creating an uneven look in the lawn.
  • Plantain: Broadleaf plantains have oval-shaped leaves that form a basal rosette. They can be persistent in lawns and are often found in compacted soil areas.
  • Chickweed: Chickweed has small, star-like white flowers and can spread rapidly in cool-season conditions. It’s often found in lawns with moist soil.
  • Henbit: Henbit produces purple flowers and is a member of the mint family. It can grow quickly and is common in lawns during the cooler months.


Can I use vinegar to kill weeds in my St. Augustine lawn?

Yes, you can use vinegar solution as a natural weed killer. You need to mix equal parts of water and vinegar and spray it directly on the weeds. However, please don’t go overboard, as it might affect the surrounding plants.

How can I prevent weeds from invading my St. Augustine lawn in the first place?

Maintaining a healthy lawn is key to preventing weed invasions. Regularly mow your grass at the recommended height, water deeply but infrequently, and fertilize appropriately. These practices should help your St. Augustine grass grow thick and strong, making it harder for weeds to make space.

Is corn gluten meal safe for St. Augustine grass and effective against weeds?

Yes, corn gluten meal is safe for St. Augustine grass. Some people use it as a natural pre-emergent herbicide. It prevents weed seeds from germinating but doesn’t affect established plants. Applying it in early spring and fall can help control weeds like crabgrass and dandelions.

Final Thoughts

We hope this guide helped you find a suitable weed killer for your St. Augustine grass and have also shared some more information that can help you grow a healthier turf. While it is always a good idea to go natural and use home remedies to eliminate stubborn and invasive weeds, it might not work if the condition is severe.

During such times, using chemical weed killers becomes the only reliable option, and to maintain the results, you can always follow it up with a pre-emergent solution.

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