St. Augustine grass is a lush, thick carpet when it’s happy, but the moment broadleaf weeds like clover, dandelion, or henbit move in, that carpet turns patchy and weak. The challenge is finding a product that feeds the grass without burning it while also eradicating the weeds—something most general-purpose lawn treatments get wrong on St. Augustine because their chemistry is too harsh for this particular warm-season turf.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. I’ve spent countless hours comparing active-ingredient safety profiles for St. Augustine, studying the granular-vs-liquid application debate, and analyzing owner feedback to separate the products that deliver balanced nutrition from those that just scorch the lawn.
A great weed-and-feed for St. Augustine combines a gentle nitrogen source with a selective herbicide that targets broadleaf weeds without damaging the grass’s sensitive stolons. This guide evaluates the best options available today, and every product here has earned its spot as a contender for the best st augustine grass weed and feed.
How To Choose The Best St Augustine Grass Weed And Feed
St. Augustine grass has a low tolerance for many common herbicides, especially those containing 2,4-D in high concentrations. The wrong product can turn your lawn yellow within days. Here’s what to scrutinize before buying.
Active Ingredient: Stick to Atrazine or Low-Dose 2,4-D
Atrazine is the gold standard for St. Augustine. It provides pre- and post-emergent control of broadleaf weeds like henbit, clover, and chickweed without harming the grass when applied correctly. Products with low-dose 2,4-D formulations (under 2%) can also work, but they require careful application on established lawns only.
Application Method: Granules vs. Liquid Concentrate
Granular weed-and-feed products are convenient for large lawns—you spread them with a broadcast spreader and water them in. Liquids, typically concentrates you mix with water and apply with a hose-end sprayer, offer more precise coverage on individual weeds and are better for spot-treating small patches.
Coverage Rate and Lawn Size
Check the coverage per bag or bottle. A standard product covers 5,000 square feet. If your lawn is smaller, you’ll waste product; if larger, you’ll need multiple units. Also look for the nitrogen-phosphorus-potassium (NPK) ratio—St. Augustine thrives with a slow-release nitrogen source that feeds across several weeks.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Southern Ag Atrazine Weed Killer | Liquid Concentrate | Full-lawn coverage | 128 oz concentrate (treats up to 5,000+ sq ft) | Amazon |
| Fertilome Weed Free Zone | Liquid Concentrate | Stubborn weeds (creeping charlie) | 32 oz; controls 80+ broadleaf weeds | Amazon |
| Scotts Turf Builder Weed and Feed | Granules | Large lawn convenience | 5,000 sq ft granular coverage | Amazon |
| Hi-Yield Atrazine Weed Killer | Liquid Concentrate | Spot-treating annual bluegrass | 32 oz; ready-to-spray bottle | Amazon |
| Preen Lawn Crabgrass Control | Granules | Crabgrass prevention | 15 lb; covers 5,000 sq ft | Amazon |
In‑Depth Reviews
1. Southern Ag Atrazine St. Augustine Grass Weed Killer
This gallon jug of atrazine concentrate is the top-tier choice for St. Augustine owners who want comprehensive pre- and post-emergent weed control. Atrazine is specifically labeled for St. Augustine and centipede grass, meaning you can apply it across the entire lawn without worrying about chemical burn. The 128-ounce volume covers a significant area—roughly 5,000 square feet per gallon—making it a cost-effective solution for medium to large lawns.
Southern Ag’s formulation targets a wide range of broadleaf weeds including henbit, clover, and chickweed while also suppressing early-stage crabgrass. The liquid concentrate mixes easily with water in a standard pump or hose-end sprayer. Because it works both as a pre-emergent (killing weed seeds before they sprout) and a post-emergent (killing already-growing weeds), you get season-long protection from a single application.
One thing to note: atrazine should not be applied to newly sodded or over-seeded St. Augustine until the lawn is fully established (after three or four mowings). Users report visible weed die-off within two to three weeks, with the grass recovering strongly. This product does not contain fertilizer, so you’ll need a separate feeding schedule—but the weed control is unmatched for this grass type.
What works
- Atrazine is one of the safest herbicides for St. Augustine
- Large 1-gallon format offers great value per square foot
- Both pre- and post-emergent action controls weeds at multiple stages
What doesn’t
- Requires a separate fertilizer—no feeding component
- Not for use on newly laid sod or weak lawns
2. Fertilome Weed Free Zone (32 oz)
Fertilome Weed Free Zone is the go-to option when you’re dealing with stubborn weeds that laugh at milder herbicides—especially creeping charlie, which many standard atrazine products struggle against. Its active ingredient is dicamba, a selective herbicide that delivers visible injury to broadleaf weeds within hours of application. The label claims control of over 80 broadleaf species, including clover, spurge, chickweed, and thistle.
This product is safe on a range of warm-season grasses, but the label explicitly recommends it for St. Augustine only when used on established lawns and according to strict dosage guidelines. The 32-ounce bottle is a concentrate—you mix it with water at the specified rate, and a little goes a long way. For spot-treating a moderate-sized yard, a single bottle can last multiple seasons.
User feedback emphasizes that this is the only product many have found effective against creeping charlie, which is notoriously resistant. The trade-off is that dicamba is less forgiving than atrazine—over-application or spraying during hot weather can cause temporary discoloration of the St. Augustine. Start with the lightest recommended mixture and test a small patch before full coverage.
What works
- Exceptional against creeping charlie and other deep-rooted broadleaf weeds
- Visible results within hours of application
- Concentrated formula provides many treatments per bottle
What doesn’t
- Requires careful mixing—too strong can damage St. Augustine
- No fertilizer included
3. Scotts Turf Builder Weed and Feed 3, 5,000 sq. ft.
Scotts Turf Builder Weed and Feed is the most recognizable name in the category, and this formula is built around a dual-action approach: fertilize the lawn while killing dandelions and clover. The active ingredients are 2,4-D and mecoprop (MCPP), both selective broadleaf herbicides. Scotts claims this version is up to twice as powerful on dandelions and clover compared to its previous formula, thanks to its Weedgrip Technology.
For St. Augustine owners, this product requires caution. The 2,4-D concentration (1.22%) is on the lower end, but it’s still harsher than atrazine. Apply it strictly on dry, established St. Augustine when temperatures are below 85°F to minimize the risk of burn. The granular format is ideal for large, even lawns—just run a broadcast spreader and water in the granules to activate the herbicide.
The feeding component is a real advantage: the nitrogen fortifies the grass to outcompete future weeds, reducing the need for multiple follow-up treatments. However, because the herbicide targets only a limited number of weeds (dandelion and clover are specifically named), it’s not a comprehensive solution. If your lawn has henbit or chickweed, you may need a supplementary product.
What works
- Combines fertilizer with weed control in one easy spread
- Weedgrip Technology improves herbicide adhesion to weed leaves
- Thickens lawn to naturally reduce weed pressure
What doesn’t
- 2,4-D can stress St. Augustine if applied in heat or on weak turf
- Limited weed-species coverage compared to atrazine
4. Hi-Yield (33431) Atrazine Weed Killer RTS (32 oz)
Hi-Yield Atrazine Weed Killer is the budget-conscious entry that doesn’t compromise on chemical safety for St. Augustine. This ready-to-spray bottle connects directly to your garden hose—no measuring, no mixing—making it one of the most user-friendly options on this list. The spray pattern delivers a consistent dose of atrazine across the targeted area, covering up to 3,720 square feet per bottle.
Users specifically praise this product for controlling annual bluegrass (Poa annua) in St. Augustine lawns. Annual bluegrass is a cool-season weed that stands out like a sore thumb in warm-season turf. The atrazine works slowly—it can take up to three weeks to see full results—but it kills the weed without harming the St. Augustine stolons. Many experienced users report that this is their go-to spring treatment for cleaning up winter weeds.
The main limitation is coverage: at 32 ounces, you get about three-quarters of an acre’s worth of treatment, which is fine for suburban lots but not for larger properties. The ready-to-spray nozzle is convenient, but it can be hard to judge exactly how much product you’re applying in each pass. When using, mark your spray path and overlap slightly to ensure even coverage.
What works
- No mixing required—screw onto hose and spray
- Excellent at killing annual bluegrass in St. Augustine
- Atrazine is gentle on established St. Augustine turf
What doesn’t
- Coverage is less than competitive liquid concentrates
- Slow-acting—takes 2–3 weeks to see full weed die-off
5. Preen Lawn Crabgrass Control – 15 lb.
Preen Lawn Crabgrass Control is a granular pre-emergent herbicide specifically formulated to stop crabgrass and over 40 other common lawn weeds before they even appear. The active ingredient, dithiopyr, is safe for St. Augustine grass when applied at the labeled rate. This product is unique on this list because it is strictly a pre-emergent—it will not kill existing weeds, but it forms a chemical barrier in the soil that prevents weed seeds from germinating.
The 15-pound bag covers 5,000 square feet, and you apply it with a standard broadcast spreader. The key timing window is early spring, when soil temperatures hit 55°F (just before crabgrass begins to germinate). Preen’s formulation allows application up to four weeks after crabgrass emerges, which is a forgiving margin compared to other pre-emergents that require perfect timing.
This product is best used as part of a two-step plan: apply Preen in early spring to prevent crabgrass, then follow with a liquid atrazine treatment later in the season for broadleaf weed control. It does not contain fertilizer, so a separate feeding regimen is required. For St. Augustine lawns that struggle specifically with crabgrass invasion each summer, this is the most effective prevention you can buy.
What works
- Prevents crabgrass all season with one early application
- Safe for St. Augustine and other warm-season grasses
- Wide application window—up to 4 weeks after emergence
What doesn’t
- No feeding component—must be paired with a fertilizer
- Will not kill existing broadleaf weeds
Hardware & Specs Guide
Active Ingredient Profiles
Atrazine is the first choice for St. Augustine because it kills broadleaf weeds pre- and post-emergently with minimal grass damage. Dicamba offers stronger control on deep-rooted weeds like creeping charlie but is less forgiving. 2,4-D blends are common in granular products but require careful temperature and timing management. Dithiopyr is a pure pre-emergent that stops crabgrass at the germination stage.
Application Methods
Granular weed-and-feed products (like Scotts) are spread with a broadcast or drop spreader and then watered in—the water activates the herbicide granules and carries the fertilizer to the roots. Liquid concentrates (like Southern Ag and Hi-Yield) are mixed with water and sprayed with a hose-end or pump sprayer. Liquids offer better leaf coverage for existing weeds, while granules provide even distribution over large areas.
FAQ
Can I use any weed and feed on my St. Augustine lawn?
How long does it take to see results after applying atrazine on St. Augustine?
Should I use granules or liquid for my St. Augustine weed and feed?
Will weed and feed kill crabgrass in my St. Augustine lawn?
Final Thoughts: The Verdict
For most gardeners, the st augustine grass weed and feed winner is the Southern Ag Atrazine Weed Killer because it delivers the safest, most comprehensive broadleaf weed control using the herbicide that St. Augustine tolerates best. If you want an all-in-one granular product that feeds and weeds simultaneously, grab the Scotts Turf Builder Weed and Feed. And for stubborn, deep-rooted weeds like creeping charlie, nothing beats the Fertilome Weed Free Zone.