Best Weed Killer for St Augustine Grass | BestLawnGear

Best weed killer for st Augustine grass (St. Augustine) is a common warm-season turfgrass that can withstand heat, humidity, and salt. It grows in USDA plant hardiness zones 8 through 10, and its wide green blades make a dense mat, creating a rich, appealing lawn.

The simplest technique to have a weed-free lawn is to do routine care such as mowing and irrigation. However, because St. Augustine is sensitive to some chemicals, you’ll need to apply a herbicide that the grass tolerates and won’t harm your lawn if weeds appear.


What Is the Best Weed Killer for St Augustine Grass

Atrazine, a member of the triazine family of herbicides, is used to control broadleaf weeds in maize fields and turfs such as residential lawns and golf courses. So, how long does atrazine take to take effect? When using atrazine to kill weeds in your yard, you should expect it to take 3 to 4 weeks.

Best Weed Killer for st Augustine Grass | BestLawnGear

If you’re using this herbicide, the best way to administer atrazine to St. Augustine grass is to apply it twice a year, in November and January, to kill both broadleaf weeds and annual grasses. 

Types of Weeds

Weeds with Broad Leaves

After your lawn has greened up in the spring, apply a herbicide to your St. Augustine grass that is designed to kill broadleaf weeds like dandelions. To avoid harm, avoid using herbicides that contain 2,4-D, mecoprop, or dicamba. Instead, look for products that contain atrazine for St. Augustine grass.

Grasses for the Cool Season

To handle cool-season grasses including crabgrass, bluegrass, and fescue, as well as small-seeded broadleaf weeds, look for a pre-emergent herbicide with dithiopyr control. When used correctly, pre-emergent herbicides can disrupt the growth process, but they should not be used on lawns that have been over-seeded with annual ryegrass.


If you’re not careful, trying to control broadleaf weeds and perennial grasses using a post-emergent herbicide that can destroy any plant it comes into contact with will also harm your St. Augustine lawn. To reduce the risk of damage to the surrounding St. Augustine grass, use a small stream of spray or apply the herbicide with a brush to specific grasses and weeds instead of a broad application.

1. Image Herbicide for St. Augustinegrass & Centipedegrass Concentrate

  • Kills the toughest weeds-down to the root Kills the weeds not the lawn when used as directed Safe on floratam lawns 32 fl. oz. covers up to 5,000 sq. ft. Fast acting, see results in hours is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.

The Image Herbicide for St. Augustine Grass is an easy-to-use concentrate that will starve your weeds to death while killing and preventing tough weeds in your St. Augustine grass.

This is a selective herbicide that targets strong broadleaf weeds in order to control grassy weeds. Image Herbicide Concentrate, which contains 4% atrazine, is efficient against weeds in Centipedegrass and St. Augustine grass.

Image Herbicide’s concentrated solution allows for a simple and quick application that kills weeds on contact and covers over 3,000 square feet. Spurweed, sandspur, and dollarweed, as well as bluegrass and Florida betony, are all controlled by it.


  • It’s difficult to find a good product for St. Augustine grass like this.
  • Weeds begin to die after a few weeks, but the grass remains healthy.
  • This product can effectively take care of out-of-control weeds, according to Image herbicide reviews, and it’s a terrific value for an excellent product.


  • For some users who only work in patches, this can be a problem.
  • There’s a fine line between too little and too much, so be cautious with amounts.

2. Ortho RTS Weed B Gon Weed Killer for St. Augustinegrass

  • For use on St. Augustinegrass including Floratam
  • Kills 250+ listed weeds (See label for listed weeds.)
  • Won’t harm the lawn – Guaranteed (When used as directed.)
  • Rain-proof in 1 hour
  • Treats up to 2,500 sq. ft. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.

Ortho Weed-B-Gone Weed Killer is one of the best weed killers for St. Augustine Grass and will effortlessly kill more than 200 weeds without harming your lawn. This easy-to-use product comes with a ready-to-use spray bottle and allows you application control over broad areas. You get a guaranteed product with Ortho Weed B Gon Weed Killer that will destroy your weeds down to their roots.

This simple product becomes rainproof in approximately an hour and does not wash away. Ortho Weed-B-Gone comes with a nozzle that is simple to attach to your hose and has a washer to keep it in place. It also has a three-way valve that allows you to clean off the nozzle by running water through it.


  • It’s simple to attach the bottle to a hose.
  • Great for use on large lawn areas. A reliable product that won’t wash away in the rain.


  • It takes a few weeks and a few rainstorms for the weeds to die.
  • There are no instructions included.

3. Bayer Advanced 704840B 3-in-1 Weed and Feed for Southern Lawns

  • Southern lawns: specially formulated for southern lawns
  • 6-Month protection: prevents broad lead, grassy weeds, and crabgrass for up to 6 months
  • Weed killer: kills weeds including dandelion, dollar weed, and clover
  • Lawn fertilizer: feeds, greens, and strengthens your lawn
  • 50% Slow release formula
  • Won't harm lawns when used as directed
  • For use on southern turfs Bermuda Grass, St Augustine Grass, Centipede Grass and Zoysia Grass is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.

Bayer Advanced Weed & Feed combines pre-emergent and post-emergent herbicides to prevent weeds from growing for up to six months. Bayer Advanced is ideal for use on St. Augustine grass, Bermuda grass, Zoysia grass, and Centipede grass, and contains an amazing fertilizer.

For as long as six months, a single application of Bayer Advanced Weed and Feed will prevent new weeds from sprouting and destroy existing weeds in your lawn, including crabgrass. This weed and feed product will also strengthen, feed, and green your lawn, resulting in thick, healthy green grass with weed control throughout the season. When used as stated, this is a basic and easy-to-use product that will not hurt your lawn.


  •  The grass is maintained in excellent shape and grows thicker.
  • The grass is kept in excellent shape and thickens.
  • When compared to its competitors, it provides the best outcomes.


  • If you’re not careful, it can harm your lawn.
  • It’s fantastic as a fertilizer, but it’s not so good on weeds.

4. Scotts Turf Builder Bonus S Southern Weed and Feed

  • Kills dollarweed, clover and other listed lawn weeds
  • Feeds grass to crowd out future weeds
  • Builds strong, deep grass roots to strengthen against heat and drought
  • Not for use on Bermudagrass
  • Only for use on St. Augustinegrass (including Floratam), centipede, zoysia and carpetgrass lawns
  • Available in TX, FL (except Panhandle region), LA, AL, GA, MS, NC, and SC. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.

Apply Scotts Turf Builder Bonus S when your grass and weeds are actively growing. Southern Weed & Feed will assist in the eradication of existing weeds while also establishing a thicker law that will prevent future weed development.

Feeding your grass with Scotts Turf Builder on a regular basis will provide it with the nutrients it requires to look its best while also assisting it in resisting weed stress. This treatment is also effective against clover and dollar weeds in extreme weather conditions such as drought and heat.

St. Augustine grass, Centipede grass, Zoysia grass, and Carpet grass are all suitable to use with Scotts Turf Builder. This is a southern lawn formula that can cover up to 5,000 square feet.


  • It works on dollar weeds.
  • Great fertilizer that aids in the regrowth of your lawn.
  • Works well on lawns with a variety of grass kinds.


  • It can’t be used around shrubs or trees.
  • Work is slow.

5. Southern Ag Atrazine St. Augustine Weed Killer

Southern Ag Atrazine Weed Killer is a broadleaf weed killer that is effective against Centipede Grass and St. Augustine Grass, as well as crabgrass. This is a pre-emergent and post-emergent treatment that can manage weeds that have already emerged as well as prevent weeds from growing.

Southern Ag Atrazine contains 4% atrazine and can cover 1,000 square feet, allowing it to control several common grass weeds. This is an efficient weed killer for St. Augustine Grass that may be used in both broad and spot applications.


  • It’s more effective than other weed killers and won’t destroy your lawn.
  • Also effective as a spot treatment.
  • The majority of weeds are eliminated with just one spray.


  • a cumbersome application system
  • For application, a hose-end sprayer would be preferable.

6. Simple Lawn Solution Commercial Grade Lawn Energizer

  • Liquid Iron, Nitrogen and Micronutrient Blend: Lawn Energizer booster provides essential nutrients needed to darken the green of your lawn
  • Covers 3,200 SQ. FT: Commercial grade intense booster treatment in a ready-to-use hose end sprayer
  • High Quality Nutrients: Lawn Energizer Booster is a 6-0-0 Nitrogen, Iron and Micronutrient blend.
  • All Grass types: Including Bermuda, St. Augustine, Zoysia, Buffalo, Centipede, Florida Palmetto, Bahia, Fescue, Ryegrass & Kentucky Bluegrass
  • Produced In The United States: Lawn Energizer is manufactured in the United States of America, by a family owned business with 25 years of former experience in the commercial professional turf industry. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.

Simple Lawn Solution’s fertilizer is a commercial-grade product that can also be used on your residential lawn.

You may expect your health, color, and development to be at their best. Your Zoysia grass lawn will be supplied with all of the necessary minerals and vitamins. This fertilizer can be used as a booster to cover 3,200 square feet with just one bottle. With the ready-to-use bottle, there’s a hose-end sprayer provided. You may fertilize your Zoysia grass lawn at any time during the growing season.

Chelated micronutrients, nitrogen, and iron combination are the major components of this product.

The iron was made available to the soil by the Chelates micronutrients, which were administered to alkaline soils.

This fertilizer can be used on Bermuda grass, centipede grass, and St. Augustine grass in addition to Zoysia grass.


  • Provides complete nutrition
  • Helps in quicker green-up
  • Treats nutrient deficiencies
  • Designed for easy application


  • Weeds may infest portions of the grass sometimes

7. Syngenta Tenacity Turf Herbicide

Mesotrione 40 percent is the active ingredient, a systemic pre-emergence and post-emergence herbicide approved by the Environmental Protection Agency for use on sod farms and golf courses. It’s approved for use as a pre-emergent and post-emergent herbicide in commercial applications.

Bentgrass, carpetweed, chickweed, clover, crabgrass, dandelion, foxtail, goosegrass, henbit, nimble grass, purslane, thistle, yellow nutsedge, and other broadleaf weeds are all killed by it.

This tiny 8-ounce container of concentrate will make 96 gallons of herbicide using just 1/2 teaspoon of concentrate per gallon of water, and it has a shelf life of 5-8 years. This equates to less than $1 per gallon.


  •  The powerful composition eliminates a wide range of weeds.
  • Excellent per gallon price


  • The syringe that comes with the kit is difficult to use.


Image Herbicide is the winner of the Best Weed Killer for St. Augustine Grass roundup. Image Herbicide is strong on weeds, preventing and killing weeds that grow in Centipedegrass and St. Augustine grass using Atrazine. This selective herbicide was developed to combat stubborn broadleaf weeds with an easy-to-apply concentrate that starves them to death.

Image Herbicide is a quick and easy-to-use herbicide that kills weeds on contact and covers an area of over 3,000 square feet. Spurweed, sandspur, and dollarweed, as well as bluegrass and Florida betony, are all targets. Image Herbicide for St. Augustine & Centipede Grass is the clear winner of the Best Weed Killer for St Augustine Grass roundup.


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