St Augustine grass is a favorite of Southern lawn lovers but requires a delicate touch when it comes to weed killer. Some products will kill your grass along with the weeds!
No need to wander the hardware store staring at instructions because we’ve got you covered.
In this article we’re going to cover our 5 favorite weed killers for St Augustine grass with thorough reviews, handy informational content, and FAQs.
Top Weed Killers for St Augustine Grass – Reviews
1. Scotts 26008A Turf Builder Southern Triple Action
Scotts usually comes in on our top 5 lists because they try to provide the total package – and at a reasonable price.
We love how this formula not only kills weeds and nasty ants, but also nourishes your grass to better withstand intense heat and drought. Because the happier your lawn is, the easier it will be to prevent weeds!
Specifications:
- Active ingredient Atrazine
- Kills stubborn Southern weeds, prevents fire ants for 6 months, feeds grass for 3 months
- Combination selective post-emergent weed killer, insect killer, and lawn fertilizer
- Covers 4,000 square feet
Pros:
- Kills & prevents weeds and strengthening lawn against drought and heat
- Formulated specifically for St Augustine grass and warm climates
- Cover more grass for less money
Cons:
- Slightly more labor-intensive application
2. Southern Ag Atrazine St. Augustine Grass Weed Killer
Specifically formulated for St Augustine grass, this atrazine-based weed killer from Southern Ag is highly for killing weeds and preventing those that germinate by seed. It’s as simple as mix and spray, and you should begin seeing results within a week.
It is less labor intensive to apply, but the bottle doesn’t go very far for folks with big yards. A 1-gallon bottle will only get 1,000 square feet.
Also, due to the toxicity of the product we don’t necessarily recommend this option for families with pets and kids.
Specifications:
- Active ingredient Atrazine
- Kills many common broadleaf and grassy weeds
- Selective post-emergent weed killer, mild pre-emergent control
- Covers 1,000 square feet
Pros:
- Kills weeds and helps prevent growth
- Easy to apply
- Formulated specifically for St Augustine grass
Cons:
- Must use caution mixing and applying
- More money to cover less grass
3. Scotts 26003 Turf Builder Triple Action
Here, we have another excellent example of weed killer that also increases your lawn’s ability to fend off weeds by itself from Scotts.
Folks who struggle with crab grass and broadleaf weeds will love this triple action formula. It kills already sprung weeds, prevents weeds and crabgrass, and fertilizes lawns!
This formula is not specifically designed for St Augustine grass, and is suited best to Northern climates. It will not harm your lawn but is not the best option for those in the deep South.
Specifications:
- Kills most common broadleaf weeds and prevents crabgrass for 4 months
- Combination selective pre-emergent & post-emergent weed killer, plus fertilizer
- Covers 4,000 square feet
Pros:
- Safe for St Augustine grass
- Kills & prevents weeds while strengthening lawn
Cons:
- Slightly more labor intensive
- Better for Northern climates and grasses
4. Southern Ag Amine 2,4-D WEED KILLER
For the most bang for your buck against post-emergent weeds, check out Southern Ag’s incredibly powerful and cost-effective weed killer. 2-3 tablespoons mixed with water will cover 1,000 square feet!
Do keep in mind however, that this effectiveness is due to the high potency and toxicity of the product. Take those provided directions as unbreakable commandments, or you may hurt your lawn, surrounding plants, the environment or local wildlife.
We do not recommend this to families with small children or pets.
Specifications:
- Active ingredient 2,4-D
- 1-4 pints of product per acer
- Selective, post-emergent weed killer
- Effective for many broadleaf weeds and woody plants
Pros:
- Safe for use on St Augustine grass
- Covers huge amount of lawn
Cons:
- Only effective for post-emergent weeds
- Highly toxic, not for use with pets and children
- Repeated use may damage lawn
5. Espoma Organic Weed Preventer
Those with pets and children that love playing on the lawn will want to go for a non-toxic formula, like Espoma. This brand is well respected in organic growing circles and families alike for their safe and effective products.
The corn gluten is spread across the lawn and does a great job of preventing common weeds and nourishing the lawn. However, this product will not take out any post-emergent weeds.
Specifications:
- Corn gluten meal formula
- Combination general pre-emergent weed control and lawn fertilizer
- Covers 1,250 square feet
- Certified organic
Pros:
- Safe for all grass types
- Prevents weed growth and strengthens lawn
- Completely non-toxic, safe for pets and children
Cons:
- Does nothing to post-emergent weeds
- More expensive
- Covers less lawn
Buyers Guide
A Little About St Augustine Grass
St Augustine grass is native to the coasts of the Gulf of Mexico and the Mediterranean. The blades are broad and flat and form a thick, springy mat.
This grass spreads quickly through above ground runners but is easy to control. It is one of the most shade tolerant turfgrasses, though it still requires at least 4 hours of sun per day.
St Augustine grass goes through a winter dormancy when it turns brown and is inactive. When temperatures rise, it puffs back up and quickly becomes green for Spring and Summer.
Unlike some turfgrass, St Augustine is best planted as plugs, sprigs, or sod. Sod will give you an almost instantaneous plus, green lawn. But with proper care, both sprigs and plugs will fill in rapidly and densely.
Check out Franklin Hernandez’s video for more on the care and keeping of St Augustine grass.
Different Types of Weed Killers Safe for St Augustine Grass
Before we get into the types, we wanted to stress the importance of thoroughly reading the label of any weed killers you plan to use.
St Augustine grass is known for being sensitive to certain chemicals, so be sure that any herbicide you use specifically states it is safe for this type of grass.
Do not apply any type of weed killer to drought stressed grass, as this only heightens the danger of damaging your lawn.
The label is law! Follow the directions as closely as possible to prevent harming your St Augustine grass, environment, and local wildlife, as well as yourself.
Pre-emergent weed killers
Pre-emergent herbicides are usually a granular or liquid product that you spread over the lawn to stop weeds from ever developing. This is the most effective type for the sensitive St Augustine grass.
You can apply a weed preventer in the grass’ dormant season, when it is brown, and avoid stressing it out with chemical sprays.
However, it will do nothing against weeds that have already sprung up.
Pre-emergent weed killer chemicals safe for St Augustine Grass include:
- Benefin
- Dithiopyr
- Isoxaben
- Oryzalin
- Prodiamine
Post-emergent weed killers
This type of weed killer is for – you guessed it – weeds that have emerged from the ground already.
Many of the most pernicious weeds will start popping up before your St Augustine grass is out of dormancy. If possible, apply a safe, post-emergent weed killer when the grass is still brown.
If you’ve waited too long, however, this type is best to apply when the grass is fully green and at its most robust and well irrigated.
Post-emergent weed killer chemicals safe for St Augustine grass include:
- 2,4-D
- Atrazine
- Bentazon
- Halosulfuron
- Imazaquin
Frequently Asked Questions
Are there weed control alternatives for St Augustine grass that don’t involve weed killer?
Most definitely! Besides pre-emergent weed killer or weed preventers, the most effective way to control weeds on St Augustine grass is to keep your lawn healthy and happy.
That means:
- Irrigate appropriately: keep an eye out for drought stress signs, and water your lawn as weather, season, and rainfall dictates
- Mow regularly: this grass does best at heights between 2-4 inches, so get a regular mowing schedule. Don’t remove more than 1/3 per mow, keep mower blade sharp, and mulch the clippings to leave on the lawn as fertilizer
- Fertilize your lawn: begin fertilizing after the last frost and consider applying more every eight weeks. Test your soil nutrients or go for a complete lawn fertilizer.
For more in-depth care and weed control instructions, check out Clemson University’s St Augustine Grass Yearly Maintenance Program.
How often should I apply weed killer to St Augustine grass?
The short answer is that most experts recommend treating your lawn with weed killer no more than twice yearly.
But always follow the directions on your weed killer’s label. If the brand you choose says once a year, then don’t go for two just to be sure – you could seriously damage you lawn and the local wildlife.
As mentioned above, the two best times are in the offending weed’s dormant period and right before they usually start popping up.
Are there pet safe alternatives to chemical and toxic weed killer for St Augustine grass?
Yes! The best pet safe weed killer for St Augustine grass is the pre-emergent kind. There are many brands, like the Espoma Organic Weed Preventer made from corn gluten meal, which will prevent weed seedlings from popping up out of the ground and fertilize your lawn at the same time.
There are many effective and usually vinegar based port-emergent weed killers as well, like Green Gobbler. Unfortunately, they are all non-specific. That means you need to be extra careful when spraying, because it will kill anything it touches!
For more options, check out our article, the Top 5 Best Pet Safe Weed Killers for 2020.
Conclusion
The finnicky, warm weather St Augustine grass needs a little extra care when selecting a weed killer. That’s why we love Scotts 26008A Turf Builder. This Southern specific formula attacks weeds in three ways: killing them, preventing them, and encouraging healthy grass growth.
Whether you’re getting rid of broadleafs, crab grass, or just trying to give your grass the space and nutrients it needs – there’s an effective and safe weed killer for St Augustin grass out there for you!
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