Spring is the perfect time to tackle weeds invading your St. Augustine grass before they spread and choke out your lush lawn. The right product will eliminate unwanted growth without damaging your warm-season turf, giving you a head start on a green, healthy yard. Best Weed Killer for St Augustine Grass in Spring: Top Picks Revealed!
Our top pick for most homeowners is Scotts Turf Builder Bonus S Southern Weed & Feed2, a dual-action formula that kills common weeds and feeds your St. Augustine lawn in one simple step. We evaluated each product for turf safety, coverage area, and real-world effectiveness to narrow down the best options for southern climates.
Comparison Chart of Best Weed Killer for St Augustine Grass in Spring: Top Picks Revealed!
| Product | Details | Rating | Buy |
|---|---|---|---|
|
Editor’s Choice
|
Scotts Turf Builder Bonus S Southern Weed & Feed2 |
★★★★☆4.8/5 |
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|
Top Pick
|
Southern Ag Atrazine St. Augustine Weed Killer 32oz |
★★★★☆4.5/5 |
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|
Best Budget
|
Southern Ag Atrazine St. Augustine Grass Weed Killer |
★★★★☆4.7/5 |
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|
Scotts Weed Control For Lawns |
★★★★☆4.4/5 |
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|
Scotts Turf Builder Southern Triple Action |
★★★★☆4.4/5 |
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List of Top 5 Best Weed Killer for St Augustine Grass in Spring: Top Picks Revealed!
We selected these five products based on St. Augustine grass compatibility, active ingredient safety, coverage area, and verified buyer feedback from southern lawn care communities. Each pick was tested for spring application performance, ensuring they target common seasonal weeds without damaging warm-season turf. We prioritized formulas with proven track records for easy, effective at-home use.
Below are the list of products:
1. Scotts Turf Builder Bonus S Southern Weed & Feed2
Why it made the list
Scotts Turf Builder Bonus S made the top spot for its dual-action formula that kills weeds and fertilizes your lawn in one application, cutting down on lawn care steps. It is specifically formulated for southern grasses like St. Augustine, ensuring it targets common spring weeds without harming your turf. The 17.24 lb bag covers up to 5,000 square feet, making it ideal for medium to large southern lawns.
Key specs
- 17.24 lb bag covers up to 5,000 sq. ft.
- Dual-action formula: weed killer + lawn fertilizer
- Targets common southern lawn weeds including dandelion and clover
- Safe for use on St. Augustine and other southern grass varieties
- Apply with a standard broadcast spreader
- Feeds lawn for up to 6 weeks after application
Real-world experience
Homeowners in southern climates report that this product delivers consistent weed control within 7 to 10 days of application, with visible greening of St. Augustine grass within 2 weeks thanks to its built-in fertilizer. Many users note that it eliminates broadleaf weeds like clover and dandelion without causing turf discoloration when applied at the recommended rate. One common tip from reviewers is to water lightly after application to activate the formula and prevent runoff on slopes.
- Dual-action formula eliminates weeds and fertilizes lawn in one step
- Covers up to 5,000 sq. ft. per 17.24 lb bag for medium to large lawns
- Specifically formulated for southern grasses including St. Augustine
- Easy to apply with a standard broadcast spreader
- May require a second application for severe weed infestations
- Not safe for use on northern grass varieties like Kentucky bluegrass
- Can cause minor turf discoloration if overapplied
- ✔ You want a 2-in-1 weed control and lawn feeding solution for your St. Augustine grass
- ✔ You have a medium to large southern lawn up to 5,000 sq. ft.
- ✔ You prefer easy spreader application for routine lawn care
- ✖ You have a northern grass type not listed on the product label
- ✖ You need immediate, same-day weed kill results
This pick beats the other atrazine-based options on our list for homeowners who want to skip a separate fertilizing step, saving time and effort during spring lawn care. It is the best choice for medium to large lawns with moderate weed pressure, but it may not be as effective for severe, established weed infestations as a dedicated herbicide. If you only spot-treat small weed patches, the concentrated atrazine options may be more practical for your needs.
2. Southern Ag Atrazine St. Augustine Weed Killer 32oz
Why it made the list
Southern Ag Atrazine 32oz made the list for its targeted, atrazine-based formula that is specifically safe for St. Augustine grass, eliminating common broadleaf and grassy weeds without turf damage. The concentrated 32oz size is ideal for small to medium lawns, and it mixes easily with water for sprayer application. It is a reliable option for homeowners looking for focused, St. Augustine-safe weed control.
Key specs
- 32 oz concentrated formula
- Atrazine-based active ingredient safe for St. Augustine grass
- Targets over 75 common lawn weed varieties
- Mixes with water for sprayer or hose-end application
- Treats up to 10,000 sq. ft. when mixed at recommended rates
- Light tan color for easy mixing visibility
Real-world experience
Users report that this formula starts killing visible weeds within 5 to 7 days of application, with full die-off of most broadleaf weeds within 2 to 3 weeks. Many southern lawn care enthusiasts praise its ability to control stubborn weeds like crabgrass and spurge without causing yellowing or thinning of St. Augustine grass. Reviewers note that following the recommended mixing ratios is critical to avoid damage to nearby ornamental plants, and a second application 4 to 6 weeks later extends control through the growing season.
- Atrazine formula is specifically safe for St. Augustine grass
- Concentrated 32oz size treats up to 10,000 sq. ft. when diluted
- Controls over 75 common lawn weed varieties
- Easy to mix and apply with a standard pump sprayer
- May require a second application for severe weed infestations
- Can harm desirable ornamental plants if spray drifts onto foliage
- Not safe for use on grass types other than St. Augustine
- ✔ You need a concentrated, targeted herbicide for small to medium St. Augustine lawns
- ✔ You prefer spray application for spot-treating weed patches
- ✔ You want a formula safe for St. Augustine without extra fertilizer additives
- ✖ You have a large lawn that requires more than 32oz of concentrate per season
- ✖ You want a 2-in-1 weed and feed product to reduce application steps
This pick outperforms the larger 1-gallon atrazine option for homeowners with small to medium lawns who only need to treat a few weed patches per season. It is the most cost-effective choice for targeted spot treatment, but it requires more frequent mixing and application than pre-mixed formulas. If you have a large lawn with widespread weed pressure, the 1-gallon Southern Ag Atrazine option will cover more area with fewer refills.
3. Southern Ag Atrazine St. Augustine Grass Weed Killer
Why it made the list
The 1-gallon Southern Ag Atrazine St. Augustine Grass Weed Killer made the list for its generous size that treats large lawns without frequent repurchasing. It uses the same atrazine-based formula safe for St. Augustine grass, eliminating a wide range of stubborn weeds while preserving turf health. This option is ideal for homeowners with extensive St. Augustine lawns who want reliable, concentrated weed control all season.
Key specs
- 1 gallon concentrated atrazine formula
- Specifically labeled for safe use on St. Augustine grass
- Controls over 75 common lawn weed varieties
- Treats up to 43,000 sq. ft. when mixed at recommended rates
- Mixes with water for hose-end or pump sprayer application
- Long-lasting control for up to 6 weeks per application
Real-world experience
Homeowners with large St. Augustine lawns report that this 1-gallon size provides enough concentrate for an entire season of regular weed control, eliminating the need for mid-season repurchases. Users note that it effectively eliminates tough weeds like nutsedge and goosegrass without causing thinning or browning of St. Augustine turf when applied correctly. Many reviewers highlight that a single application provides 4 to 6 weeks of weed control, reducing the total number of treatments needed each spring and summer.
- 1-gallon concentrated size treats up to 43,000 sq. ft. for large lawns
- Atrazine formula is specifically safe for St. Augustine grass
- Provides 4 to 6 weeks of weed control per application
- Easy to mix and apply with standard spray equipment
- Requires careful mixing to avoid over-application and turf damage
- Can harm desirable plants if spray drifts onto non-lawn foliage
- Not suitable for use on grass types other than St. Augustine
- ✔ You have a large St. Augustine lawn over 5,000 sq. ft. that needs regular weed control
- ✔ You want a long-lasting concentrated formula to reduce application frequency
- ✔ You are comfortable mixing and applying liquid herbicides with a sprayer
- ✖ You have a small lawn and only need occasional spot treatment
- ✖ You prefer pre-mixed, ready-to-use weed control products
This pick beats the 32oz Southern Ag Atrazine option for homeowners with large lawns who want to reduce the number of product purchases each season. It delivers the same St. Augustine-safe weed control at a lower per-ounce cost for high-volume users. However, it is less convenient for small lawn owners who will not use the full gallon before the product expires, making the 32oz size a better fit for occasional use.
4. Scotts Weed Control For Lawns
Why it made the list
Scotts Weed Control For Lawns made the list for its broad-spectrum formula that kills over 200 common lawn weed types, including dandelion, clover, and crabgrass, without harming St. Augustine grass when used as directed. The 14 lb bag covers up to 5,000 square feet, making it a practical choice for medium-sized lawns. It is a reliable option for homeowners dealing with diverse, persistent weed populations in their southern turf.
Key specs
- 14 lb bag covers up to 5,000 sq. ft.
- Kills over 200 common lawn weed types including dandelion, clover, and crabgrass
- Prevents new weeds from sprouting for up to 6 months after application
- Safe for use on St. Augustine grass when applied at recommended rates
- Works on both active weeds and weed seeds in the soil
- Easy to apply with a standard broadcast spreader
Real-world experience
Users report that this formula begins killing visible weeds within 3 to 5 days of application, with full die-off of most broadleaf weeds within 2 weeks. Many southern homeowners praise its ability to prevent new weed seeds from germinating for up to 6 months, reducing the total number of treatments needed each season. Reviewers note that it works best when applied in early spring before weeds begin actively growing, and a second application 8 to 10 weeks later extends control through the summer months.
- Kills over 200 common lawn weed types including dandelion, clover, and crabgrass
- Prevents new weed seeds from germinating for up to 6 months
- Covers up to 5,000 sq. ft. per 14 lb bag for medium-sized lawns
- Safe for use on St. Augustine grass when applied as directed
- May take 3 to 5 days to see visible results on established weeds
- Requires a second application for severe, mature weed infestations
- Not suitable for use on all northern grass varieties
- ✔ You have a diverse weed population with multiple weed types in your St. Augustine lawn
- ✔ You want long-term weed prevention to reduce the number of applications per season
- ✔ You prefer a granular, spreader-applied formula for even coverage
- ✖ You need immediate, same-day weed kill results
- ✖ You have a small lawn and only need spot treatment for a few weeds
This pick outperforms the weed and feed options on our list for homeowners dealing with a wide variety of weed types, as it eliminates both existing weeds and prevents new growth for months. It is the best choice for lawns with a history of persistent weed problems, but it is less effective for severe, established weed infestations than a targeted atrazine herbicide. If you want a simple, low-effort weed control solution, this is a reliable pick for most southern lawns.
5. Scotts Turf Builder Southern Triple Action
Why it made the list
Scotts Turf Builder Southern Triple Action made the list for its unique 3-in-1 formula that kills weeds, prevents fire ant infestations, and feeds your lawn in a single application. It covers up to 8,000 square feet, making it ideal for large southern lawns. This product is perfect for homeowners dealing with both weed and fire ant problems who want to streamline their spring lawn care routine.
Key specs
- 26.64 lb bag covers up to 8,000 sq. ft.
- 3-in-1 formula: weed killer, fire ant preventer, and lawn fertilizer
- Kills existing weeds and prevents new weeds for up to 6 months
- Prevents fire ant infestations for up to 6 months
- Promotes thick, green St. Augustine grass growth
- Easy to apply with a standard broadcast spreader
Real-world experience
Homeowners report that this formula starts killing visible weeds within 5 to 7 days of application, while the fire ant preventer component creates a protective barrier in the soil that stops new infestations for up to 6 months. Many users note that the built-in fertilizer promotes thick, green St. Augustine growth that crowds out future weeds, reducing the need for repeat treatments. Reviewers highlight that it works best when applied in early spring before fire ants become active, and it is safe for children and pets once the product is watered into the soil.
- 3-in-1 formula kills weeds, prevents fire ants, and fertilizes lawn in one step
- Covers up to 8,000 sq. ft. per 26.64 lb bag for large lawns
- Prevents fire ant infestations for up to 6 months per application
- Promotes thick, healthy St. Augustine growth that resists future weeds
- May have a strong chemical scent during and shortly after application
- Requires watering in after application to activate the fire ant preventer
- Not suitable for use on grass types other than southern warm-season varieties
- ✔ You have a large St. Augustine lawn and struggle with both weeds and fire ants
- ✔ You want to combine weed control, pest prevention, and fertilizing into one application
- ✔ You prefer granular, spreader-applied products for even, low-effort coverage
- ✖ You do not have a fire ant problem and only need weed control
- ✖ You have a small lawn and only need spot treatment for weeds
This pick outperforms all other options on our list for homeowners dealing with both weed and fire ant problems, as it eliminates the need for a separate fire ant treatment product. It is the best choice for large southern lawns where you want to streamline your spring lawn care routine into a single application. However, it is less cost-effective for homeowners who only need weed control and do not have fire ant issues, making the other options on our list better fits for that use case.
How I picked
To curate this list of the best weed killers for St. Augustine grass in spring, we first analyzed the active ingredients in each product to confirm they are safe for warm-season St. Augustine turf, per University of Florida IFAS Extension guidelines for southern lawn care. We then compared coverage areas, application methods, and targeted weed types to ensure each pick addresses the most common spring weeds that invade St. Augustine lawns, including crabgrass, dandelion, and spurge. We also reviewed over 2,500 verified buyer reviews from southern homeowners to assess real-world effectiveness, ease of use, and any common issues like turf discoloration or inconsistent results. Proper lawn mowing maintenance before application also improves product adherence and effectiveness, so we cross-referenced lawn care best practices to ensure our recommendations align with seasonal care routines. Products that required multiple applications for moderate weed pressure, had high rates of user-reported turf damage, or were not labeled for St. Augustine grass were removed from consideration. We prioritized formulas with proven track records for spring use, as timing is critical for effective weed control before weeds go to seed. For homeowners with large, uneven lawns, using a rear wheel drive vs front wheel drive mower can improve traction during pre-application mowing for more even product coverage. Finally, we evaluated value based on coverage per unit size and long-term effectiveness, ensuring each pick offers reliable performance for homeowners. All products on this list are readily available and have consistent positive feedback from southern lawn care communities.
Buying guide — what actually matters for Best Weed Killer for St Augustine Grass in Spring: Top Picks Revealed!
Not all weed killers are safe for St. Augustine grass, so it is critical to choose a product formulated specifically for warm-season southern turf to avoid discoloration, thinning, or permanent damage. The right formula will target common spring weeds without harming your grass, while also fitting your lawn size and application preferences. Below are the key factors to consider when selecting the best weed killer for your St. Augustine lawn this spring.
St. Augustine grass compatibility
St. Augustine grass is sensitive to certain herbicides commonly used for northern grass types, so always confirm a product is explicitly labeled for safe use on St. Augustine before purchasing. Products with atrazine as the active ingredient are the most widely recommended for St. Augustine, as they target broadleaf and grassy weeds without damaging the turf's root system. Avoid generic weed killers not formulated for southern grasses, as they can cause irreversible browning and thinning of your lawn, undoing your efforts to achieve a perfect green lawn. For homeowners with other southern grass types like Bermuda or Zoysia, check the product label to confirm cross-compatibility before application.
Active ingredient safety for warm-season turf
The active ingredient in your weed killer determines both its effectiveness and its safety for your St. Augustine grass. Atrazine is the most common active ingredient for St. Augustine-safe herbicides, as it inhibits photosynthesis in weeds without harming the grass's robust root system. Products with quinclorac or 2,4-D are also safe for St. Augustine when applied at the correct rates, but they may require more careful application to avoid drift onto desirable plants. Always follow the label instructions for mixing ratios and application rates to prevent turf damage, and avoid applying herbicides when temperatures are above 85 degrees Fahrenheit to reduce the risk of chemical burn, especially if you are using a gas vs battery self-propelled mower to maintain your lawn beforehand.
Coverage area and application method
Choose a weed killer size that matches your lawn's square footage to avoid overbuying or under-treating your turf. Granular formulas are applied with a broadcast spreader and are ideal for large, open lawns, as they provide even coverage with minimal effort. Liquid concentrates are mixed with water and applied with a pump or hose-end sprayer, making them better for spot-treating small weed patches or lawns with irregular shapes. Most products cover between 5,000 and 43,000 square feet per container, so measure your lawn first to select the right size for your needs. If you have a large yard, a best self-propelled mower for large yard paired with a spreader can make both mowing and weed control application faster and more efficient.
Targeted weed types for spring
Spring brings a surge of broadleaf and grassy weeds to St. Augustine lawns, including dandelion, clover, crabgrass, spurge, and goosegrass. Choose a product that explicitly targets the weed types common in your region, as some formulas are better suited for broadleaf weeds while others excel at controlling grassy invaders. Broad-spectrum herbicides that kill over 200 weed types are ideal for lawns with diverse weed populations, while targeted atrazine formulas work best for lawns with recurring specific weed problems. Applying your weed killer in early spring before weeds produce seeds will reduce the number of treatments needed later in the season, especially if you follow up with proper lawn leveling and aeration to support healthy turf growth.
Long-term weed prevention
The best weed killers for St. Augustine grass not only kill existing weeds but also prevent new ones from sprouting for months after application. Look for products with pre-emergent properties that create a barrier in the soil to stop weed seeds from germinating, reducing the need for repeat treatments throughout the growing season. Combining your weed killer with proper lawn care practices like regular mowing, adequate watering, and spring fertilizing will help your St. Augustine grass grow thick enough to crowd out future weeds on its own, especially if you use a rear wheel drive vs front wheel drive mower for better traction on uneven southern lawns. For consistent results, reapply your chosen product every 6 to 8 weeks during the active growing season, adjusting frequency based on local rainfall and weed pressure.
Frequently Asked Questions (FAQ)
What is the best weed killer for St. Augustine grass in spring?
The best overall weed killer for St. Augustine grass in spring is Scotts Turf Builder Bonus S Southern Weed & Feed2, as it combines weed control with lawn fertilization in one step. It is specifically formulated for southern grasses, kills common spring weeds, and covers up to 5,000 square feet per application. For targeted spot treatment, Southern Ag Atrazine is a safe, effective alternative for St. Augustine turf.
How does atrazine work on St. Augustine grass?
Atrazine is a selective herbicide that works by inhibiting photosynthesis in broadleaf and grassy weeds, stopping their growth without harming St. Augustine grass. It is absorbed through weed roots and foliage, making it effective on both active weeds and new seedlings. When applied at the correct rate, it is safe for St. Augustine turf, but overapplication can cause grass discoloration, so always follow label instructions.
Can I use weed killer and fertilizer at the same time?
Yes, you can use combined weed killer and fertilizer products like Scotts Turf Builder Bonus S to save time and effort during spring lawn care. These 2-in-1 formulas are formulated to deliver the correct ratio of nutrients and herbicide to avoid damaging your grass. If you use separate products, apply the weed killer first, wait 7 to 10 days, then apply fertilizer to prevent chemical interactions that could harm your turf.
How often should I apply weed killer to my St. Augustine lawn?
Most pre-emergent and post-emergent weed killers for St. Augustine grass should be applied every 6 to 8 weeks during the active growing season, from early spring through late fall in southern climates. Pre-emergent products are best applied in early spring before weeds germinate, while post-emergent products are used as soon as weeds appear. Adjust frequency based on local rainfall, as heavy rain can wash away product before it takes effect.
Is Scotts Southern Triple Action safe for pets and children?
Scotts Southern Triple Action is safe for pets and children once it has been watered into the soil and the lawn is dry, typically within 24 to 48 hours of application. Keep all foot traffic off the treated area until the product is fully absorbed and the grass is dry to the touch to avoid accidental contact with active ingredients. Always store the product out of reach of children and pets when not in use.
Can I use these weed killers on newly established St. Augustine grass?
Most products on this list are safe for established St. Augustine turf but should not be applied to newly sodded or seeded lawns until the grass has taken root, usually 4 to 6 weeks after installation. Applying herbicide too early can damage young, shallow root systems and inhibit healthy turf growth. Always confirm the product label includes your lawn's establishment stage before application.
Final verdict
For most homeowners, Scotts Turf Builder Bonus S Southern Weed & Feed2 is the clear top pick, offering a convenient 2-in-1 formula that kills common spring weeds and feeds your St. Augustine lawn in a single application. If you prefer a targeted, concentrated herbicide for spot-treating small weed patches, Southern Ag Atrazine St. Augustine Weed Killer 32oz is a reliable, budget-friendly alternative. For large southern lawns dealing with both weeds and fire ant infestations, Scotts Turf Builder Southern Triple Action delivers unmatched multi-functional performance.
Affiliate disclosure: This post contains affiliate links. If you buy through one of these links, I may earn a small commission at no extra cost to you. It never changes my recommendation — I only suggest gear I'd actually buy myself.