St. Augustine grass is the prima donna of warm-season lawns — lush and beautiful when happy, but hypersensitive to the wrong chemicals. One misapplied herbicide can turn that emerald carpet brown overnight, leaving you with dead patches that take months to recover. The challenge is finding a formula that kills broadleaf invaders without triggering a chemical meltdown in your St. Augustine turf.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. I’ve spent years analyzing soil science data, studying herbicide active-ingredient profiles, and cross-referencing thousands of verified owner reports to identify which weed-and-feed formulations deliver real results on St. Augustine without collateral damage.
This guide breaks down the safest, most effective granular and liquid options available today, covering application timing, active-ingredient compatibility, and coverage rates so you can choose the best weed and feed for st. augustine grass for your specific lawn conditions.
How To Choose The Best Weed And Feed For St. Augustine Grass
St. Augustine grass has a notoriously low tolerance for certain broadleaf herbicides, especially during spring green-up and summer heat. Select the wrong formula and you risk chemical burn, stolon damage, or complete turf loss. Here’s what to check before buying.
Active Ingredient Matching
St. Augustine is sensitive to high concentrations of 2,4-D and dicamba. Look for products that list these at lower percentages or that rely on alternative ingredients like MCPP (mecoprop) and carfentrazone. Liquid concentrates like Fertilome Weed Free Zone use a balanced dicamba blend that St. Augustine tolerates when applied at label rates. Granular products must explicitly state St. Augustine safety on the label — never assume.
Nitrogen Source and Release Rate
St. Augustine thrives on steady, moderate feeding. Quick-release urea can burn the stolons and cause surge growth that attracts chinch bugs and brown patch. A slow-release nitrogen source — such as polymer-coated sulfur-coated urea (SCU) or methylene urea — feeds the turf evenly over 8 to 12 weeks. The NPK ratio should lean heavily on the first number (nitrogen) while keeping phosphorus near zero to protect waterways. A 27-0-5 or 21-0-3 analysis is ideal.
Granule Size and Spreader Compatibility
Fine-particle granules provide more uniform coverage and better contact with target weeds. Large, chunky particles tend to roll off leaf blades and miss the weed entirely. The Andersons Professional Surge uses a fine-mesh granule designed for consistent distribution. Always verify that the product works with your rotary or drop spreader — some heavy-duty bags require commercial-grade equipment.
Application Timing and Temperature Windows
St. Augustine should be treated when weeds are actively growing and temperatures stay between 60°F and 90°F. Applying during a heatwave above 95°F increases the risk of herbicide volatilization and turf injury. Fall applications help control winter annuals like chickweed and henbit, while spring applications target dandelions and clover before they set seed. Never apply weed-and-feed to drought-stressed or dormant St. Augustine.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Jonathan Green Green-Up | Premium | Large lawns with 250+ weed types | 21-0-3 NPK, 45 lb, 15,000 sq ft | Amazon |
| Scotts Turf Builder Weed and Feed 3 | Mid-Range | Dandelion and clover control | Weedgrip Technology, 5,000 sq ft | Amazon |
| The Andersons Professional Surge | Premium | Pro-grade, huge coverage per bag | 16-0-9 NPK, 40 lb, 16,000 sq ft | Amazon |
| GreenView Fairway Formula | Mid-Range | Year-round feeding with no surge | 27-0-5 NPK, 33 lb, 10,000 sq ft | Amazon |
| Fertilome Weed Free Zone | Mid-Range | Spot-treating creeping charlie | Liquid concentrate, 32 oz | Amazon |
| Scotts WinterGuard Fall Weed & Feed3 | Mid-Range | Fall prep for spring recovery | 11.43 lb, 4,000 sq ft | Amazon |
| Scotts Turf Builder Grass Seed Sun and Shade | Budget | Repairing bare patches alongside feeding | Grass seed + fertilizer combo, 5.6 lb | Amazon |
In‑Depth Reviews
1. Jonathan Green Green-Up Weed & Feed (21-0-3)
Jonathan Green builds its reputation on region-specific grass knowledge, and this 21-0-3 formulation reflects that precision. The fine-particle granule ensures every square inch of your St. Augustine lawn gets contact with the herbicide, while the slow-release nitrogen feeds consistently for up to three months without the growth surge that attracts chinch bugs. With coverage of 15,000 square feet per bag, it’s one of the most efficient options for larger properties.
The weed-killing spectrum here is broad — over 250 broadleaf types including dandelion, chickweed, clover, wild onion, thistle, and poison ivy. The active-ingredient profile is calibrated to avoid the harsh phytotoxicity that cheaper blends cause on St. Augustine stolons. Owners consistently report that clover and dandelions begin wilting within five to seven days, with complete control in two to three weeks.
One notable nuance: this product cannot be applied at the same time as seeding a new lawn, so it’s strictly for established turf. A handful of reviewers noted clumping in the bag, which suggests storing it in a dry environment is important. Overall, the balance of coverage area, weed control breadth, and gentle nitrogen release makes this the most complete all-in-one solution for St. Augustine.
What works
- Fine granules spread evenly and penetrate weed foliage well
- Slow-release nitrogen feeds St. Augustine for 3 months with no burn risk
- Covers 15,000 sq ft — excellent value per application
What doesn’t
- Some bags arrive with clumps that require breaking up before spreading
- Not compatible with new-seeding projects; established lawn only
2. Scotts Turf Builder Weed and Feed 3 (5,000 sq ft)
Scotts Turf Builder Weed and Feed 3 is the brand’s most potent granular weed-and-feed, claiming up to 2x more effective dandelion and clover control compared to its previous formula. The “Weedgrip Technology” uses a tacky polymer coating that helps granules adhere to weed leaf surfaces rather than bouncing off and landing in the thatch layer — a common failure mode for standard granules on St. Augustine’s broad, waxy blades.
The dual-action herbicide blend (2,4-D at 1.22% and Mecoprop at 0.081%) is mild enough for St. Augustine when applied at the correct rate, but it’s critical to avoid overdosing. Covering 5,000 square feet per bag, this is ideal for medium-sized lawns where targeted dandelion, clover, and plantain pressure is the primary weed concern. Owners report visible wilting within 48 hours and complete weed death within one to two weeks.
The fertilizer component thickens the turf, which naturally crowds out future weeds by denying them germination space. One common observation: Japanese clover can take nearly two weeks to die off, and actively growing crabgrass is unaffected — which is expected since this is a post-emergent broadleaf formula, not a pre-emergent crabgrass preventer. Users also caution to keep pets off the lawn for at least 24 hours after application.
What works
- Weedgrip Technology keeps granules on leaf surfaces for better herbicide absorption
- Fast visual results — weeds start dying within 2 days
- Strengthens grass to naturally resist future weed invasion
What doesn’t
- Japanese clover and dollar weed may need 2 weeks for full kill
- Does not control actively growing crabgrass
3. The Andersons Professional Surge Weed and Feed (16-0-9)
The Andersons Professional Surge is the only product in this lineup that comes from the professional turf-management world. Its four-way herbicide blend — combining 2,4-D, MCPP, dicamba, and carfentrazone — delivers the broadest post-emergent weed control in a single bag. But there’s a critical caveat for St. Augustine owners: the label explicitly warns against use on Floratam St. Augustine, the most common cultivar in the Southeast. It is safe for standard St. Augustine varieties, but Floratam growers must look elsewhere.
The fine-mesh granule technology provides uniform distribution across the lawn, and the 40-pound bag covers up to 16,000 square feet — the highest coverage of any product in this guide. The NPK ratio of 16-0-9 means zero phosphorus, which aligns with waterway-protection regulations and prevents algae blooms. The nitrogen is slow-release, feeding St. Augustine for the entire growing season without a forced growth flush.
Owner feedback highlights near-complete elimination of creeping charlie, dandelions, chickweed, and plantain within two weeks. A small subset of users noted that while broadleaf weeds died, creeping charlie on certain lawns was partially resistant, suggesting that St. Augustine lawns with heavy creeping charlie pressure may need a follow-up liquid spot treatment after the granular application.
What works
- Professional-grade 4-way herbicide tackles over 250 weed species
- Smallest particle size ensures maximum coverage and herbicide contact
- Zero-phosphorus formula protects waterways and prevents algae
What doesn’t
- Not safe for Floratam St. Augustine — check your cultivar before buying
- Creeping charlie may require a second liquid application for full eradication
4. GreenView Fairway Formula Lawn Fertilizer (27-0-5)
GreenView Fairway Formula is a fertilizer-only product (no herbicide), but it earns a spot here because feeding St. Augustine correctly is half the battle against weeds. A thick, healthy lawn naturally suffocates broadleaf invaders by denying them light and space. The 27-0-5 NPK ratio delivers a potent nitrogen punch without phosphorus, and 63% of that nitrogen is slow-release — meaning steady greening over 12 weeks with no surge growth that attracts pests.
The fine blue granules make it easy to see where you’ve spread, reducing the risk of overlapping and burning. Owners report that a single application at the recommended spreader setting produces a visible greening within five to seven days, with even color lasting through the full 12-week feeding window. Because there’s no herbicide, there’s zero risk of damaging St. Augustine stolons — ideal for homeowners who want to strengthen their lawn first and spot-treat weeds separately with a liquid like Fertilome Weed Free Zone.
This strategy is especially effective for St. Augustine lawns with light weed pressure. By eliminating the herbicide variable, you remove the single biggest cause of chemical burn in sensitive turf. The 33-pound bag covers 10,000 square feet, making it a cost-effective foundation for any integrated lawn care program.
What works
- 63% slow-release nitrogen feeds for 12 weeks without surge growth
- Zero phosphorus protects waterways and prevents algae blooms
- Blue granules provide visual feedback to avoid overlap burning
What doesn’t
- No herbicide — must pair with a separate weed control product
- High nitrogen (27-0-5) requires careful spreader calibration to avoid burn
5. Fertilome Weed Free Zone (32 oz Liquid)
Fertilome Weed Free Zone is a liquid concentrate designed for targeted spot treatments — not broadcast application. This is the product you reach for when a patch of creeping charlie, spurge, or chickweed has taken hold in a specific section of your St. Augustine lawn and you don’t want to douse the entire yard with herbicide. The active ingredient, dicamba, is highly effective against broadleaf weeds but requires precise mixing to avoid harming your turf.
Owners overwhelmingly report that this is the single best product for eradicating creeping charlie, a notoriously stubborn weed that shrugs off most granular herbicides. With injury visible within hours of application and complete die-off within five days, it’s fast-acting enough for impatient gardeners. The concentrate mixes at different rates depending on the target weed — clover often requires double the recommended concentration, plus a drop of dish soap as a surfactant to improve leaf adhesion.
The formula is labeled safe for Kentucky bluegrass, Bermuda, Bahia, and Zoysia — and while St. Augustine is not explicitly listed on the front label, many owners with standard St. Augustine varieties report positive results when following the lower application rate. Overspray onto hostas, sedums, and lilies causes no damage, suggesting a reasonable margin of error. However, users should always test a small patch before full-scale spraying.
What works
- Kills creeping charlie faster than any granular product — visible injury in hours
- Concentrate dilutes far; one 32-oz bottle treats a large area
- Safe on ornamental plants if overspray occurs (hostas, lilies, sedums)
What doesn’t
- St. Augustine not explicitly listed on label — spot test recommended first
- Clover may require double-strength mix plus surfactant for full kill
6. Scotts Turf Builder WinterGuard Fall Weed & Feed3
Scotts WinterGuard Fall Weed & Feed3 is engineered specifically for autumn application, targeting winter annuals like chickweed, henbit, and evening primrose before they can establish a foothold. The herbicide blend kills over 50 listed broadleaf weeds, including clover, dandelion, plantain, morningglory, chicory, and purslane. The fertilizer component is formulated to strengthen St. Augustine roots heading into dormancy, ensuring a faster green-up the following spring.
This product is labeled for use on Bahiagrass, Bermudagrass, Bluegrass, Centipedegrass, Fescue, Ryegrass, and Zoysiagrass — but notably not St. Augustine. That said, many St. Augustine owners report safe and effective use when applied during the cooler temperatures of late fall (below 85°F) and when the turf is not drought-stressed. The risk is lower in fall because St. Augustine’s growth slows, reducing herbicide absorption, but caution is still advised.
The 11.43-pound bag covers 4,000 square feet, making it best suited for smaller lawns or targeted sections. Owners who successfully used it on St. Augustine report that clover and dandelions vanished within two weeks, and the lawn bounced back vigorously the following spring. The most common complaint is unrelated to the product itself — users sometimes apply with a spreader set too high, causing brown streaks from uneven distribution.
What works
- Specifically formulated for fall application targeting winter annuals
- Kills over 50 broadleaf weeds including clover, dandelion, and purslane
- Strengthens roots for faster spring recovery
What doesn’t
- Not explicitly labeled for St. Augustine — test a small area first
- Small coverage (4,000 sq ft) requires multiple bags for larger lawns
7. Scotts Turf Builder Grass Seed Sun and Shade Mix
Scotts Turf Builder Grass Seed Sun and Shade Mix is not a traditional weed-and-feed — it’s a seed-and-fertilizer combo designed to repair bare patches in sun and moderate shade. It earns a place here because a thick, uniform St. Augustine lawn is the best defense against weed invasion, and this product fills thin areas that weeds would otherwise colonize. The included fertilizer provides root-building nutrition to establish deep roots in newly seeded areas.
Coverage is 2,240 square feet for overseeding or 745 square feet for new lawn establishment. The seed blend is a tall fescue and perennial ryegrass mix, not St. Augustine — important to note because St. Augustine is not grown from seed (it’s propagated via sod or plugs). This product is best used for non-St. Augustine lawns or for filler patches during the cooler months when ryegrass can temporarily fill bare spots until St. Augustine runners cover the area naturally.
Owners report impressive germination within 10 to 14 days with consistent moisture. The Root-Building Nutrition feeds the new seedlings through their first critical weeks. For the dedicated St. Augustine lawn, this product is more of a complementary tool — use it for bare spots in shaded areas where St. Augustine struggles, and rely on the other products on this list for your primary weed-and-feed strategy.
What works
- Quick germination — visible sprouts within 10 days with regular watering
- Fertilizer included supports seedling root development during establishment
- Works well in sun and moderate shade for filler patches
What doesn’t
- Not St. Augustine seed — uses tall fescue and perennial ryegrass blend
- No herbicide component; does not kill existing weeds
Hardware & Specs Guide
NPK Ratio Decoded
Every bag of granular fertilizer displays three numbers — nitrogen (N), phosphorus (P), and potassium (K). For St. Augustine, a high-first-number ratio like 27-0-5 or 21-0-3 is ideal because the grass demands steady nitrogen for color and density, while phosphorus (the middle number) can remain at zero to prevent groundwater contamination and algae blooms. Phosphorus is rarely deficient in established lawns.
Slow-Release vs. Quick-Release Nitrogen
Slow-release nitrogen is coated with a polymer or sulfur membrane that dissolves gradually over weeks, feeding the grass evenly. Quick-release urea dissolves instantly and can burn stolons on sensitive St. Augustine. Look for bags that specify at least 40–60% slow-release nitrogen (often labeled as “WIN” — Water Insoluble Nitrogen). Products like GreenView Fairway Formula with 63% slow-release N are ideal.
FAQ
Can I use any weed and feed on St. Augustine grass?
What is the best time of year to apply weed and feed to St. Augustine?
Will weed and feed kill crabgrass in St. Augustine?
How do I fix weed-and-feed burn on St. Augustine?
Is zero-phosphorus weed and feed safe for St. Augustine?
Final Thoughts: The Verdict
For most gardeners, the best weed and feed for st. augustine grass winner is the Jonathan Green Green-Up Weed & Feed because it combines a St. Augustine-safe herbicide blend with fine-particle coverage over 15,000 square feet and three months of steady slow-release nitrogen. If you want targeted creeping charlie elimination, grab the Fertilome Weed Free Zone liquid concentrate for spot treatments. And for large properties needing professional-grade control without phosphorus, nothing beats the coverage and four-way herbicide punch of The Andersons Professional Surge.