If you’re battling weeds in your St Augustine grass lawn, selecting the best post emergent herbicide tailored to this grass type is essential. Effective herbicides will selectively eliminate broadleaf and grassy weeds without harming your turf. Below is a summary of top herbicides specially formulated for St Augustine grass that offer broad-spectrum weed control, post-emergent and sometimes pre-emergent action, and ease of use for residential lawn care.
| Product Name | Brand | Key Features |
|---|---|---|
| Syngenta Tenacity Herbicide – 8 oz Liquid | Syngenta | Broad-spectrum, pre & post emergent, controls 46 weed species, safe for seeding |
| Mesotrione Weed Killer Concentrate – 8 oz | Petra | Post & pre emergent, targets crabgrass and broadleaf weeds, easy spray application |
| Monterey Grass Getter – 8 oz | Monterey | Selective post emergent, kills grassy weeds including crabgrass, safe for ornamentals |
| Lawn Synergy Lesco Three-Way Post Emerg. Herbicide – 1 Gallon | Lawn Synergy | Fast acting, professional strength, kills broadleaf weeds |
| Southern Ag Atrazine St. Augustine Weed Killer – 1 Gallon | Southern Ag | Controls grassy & broadleaf weeds, includes surfactant for better coverage |
Syngenta Tenacity Herbicide 8-oz Liquid for Lawns
Syngenta Tenacity Herbicide is a liquid solution designed to control a wide range of 46 broadleaf and grassy weed species, including tough offenders like crabgrass, clover, dandelion, and yellow nutsedge. What makes Tenacity unique is its ability to be applied at any time during seeding or overseeding, whether bare ground or established turf, making it versatile for lawn renovation. The active ingredient, mesotrione, is derived from a natural compound found in the bottlebrush plant.
This herbicide offers selective pre- and post-emergent control by preventing weed germination and actively targeting existing weeds while preserving your St Augustine grass. It’s formulated to treat your lawn effectively without causing harm to desirable grasses, supporting both weed prevention and removal in a single product.
Mesotrione Weed Killer Concentrate for Lawns
The Mesotrione Weed Killer Concentrate by Petra offers a potent formula for both pre- and post-emergent weed control, making it an excellent choice for St Augustine lawns. It effectively handles persistent weeds such as crabgrass, dandelion, clover, and yellow nutsedge. The liquid concentrate allows for easy spray application to ensure uniform coverage.
This concentrated herbicide is useful for keeping seedbeds weed-free during spring seeding while also managing established weed growth. Its broad spectrum targets many common lawn weeds to support a green, thick turf. Petra’s formula emphasizes ease of use and maximum effectiveness, helping homeowners maintain a weed-free St Augustine lawn with less effort.
Monterey Grass Getter 8oz – Selective Post Emergent Herbicide
Monterey Grass Getter is a selective post emergent herbicide specifically designed to control grassy weeds like crabgrass, bermudagrass, foxtail, goosegrass, and johnsongrass, which can invade your St Augustine lawn. It works systemically, killing grassy weeds down to the root without damaging desirable plants or ornamentals nearby.
This product can be sprayed directly over tolerant plants and shrubs, offering targeted control in mixed planting beds. However, it’s not recommended for application within established lawn areas because it only targets grasses and does not affect broadleaf weeds or nutsedge (nutgrass). The inclusion of a measuring spoon ensures precise mixing for optimum results.
Lawn Synergy Lesco Three-Way Post Emergent Herbicide
The Lawn Synergy Lesco Three-Way is a professional strength, fast-acting selective herbicide designed to kill most broadleaf weeds effectively. Its three-way formulation allows it to combat a wide variety of common lawn weeds, ensuring your St Augustine grass is not affected while eliminating invasive plants.
This one-gallon liquid herbicide is suitable for homeowners seeking a strong post emergent option with quick results. Its concentrated form means it covers a larger area, which is practical for medium to large lawn sizes. The formula is tailored to provide broadleaf weed control with minimal stress to turf.
Southern Ag Atrazine St. Augustine Grass Weed Killer
Southern Ag Atrazine targets both grassy and broadleaf weeds in St Augustine and centipede lawns. This herbicide is effective against many common invasive weeds and provides suppression of crabgrass. Included is a non-ionic surfactant that enhances coverage and penetration of the herbicide, making treatments more efficient.
Its targeted formulation supports St Augustine grass health while minimizing damage to the turf. This product is an excellent choice for those looking to control a wide variety of weeds with one treatment, particularly when crabgrass is a key concern. The surfactant inclusion helps ensure even application and weed mortality.
Buying Guide for Post Emergent Herbicides for St Augustine Grass
Selective Weed Control
Since St Augustine grass is sensitive to many herbicides, selecting a product with selective action ensures your grass stays healthy while unwanted broadleaf and grassy weeds are eliminated. Check the label for turf safety and compatibility with St Augustine grass.
Pre-Emergent vs Post-Emergent Action
Many herbicides offer both pre-emergent (preventive) and post-emergent (active) weed control. Depending on lawn conditions, choose a product that matches your needs. Post emergent herbicides target existing weeds, while pre-emergent types help prevent future weed germination, benefiting overseeded or newly seeded lawns.
Weed Spectrum
Consider which weeds primarily affect your lawn—crabgrass, dandelion, nutsedge, clover, or others—and confirm that the herbicide is labeled to control those species. Broad-spectrum products cover many weeds but always verify specific control on the label.
Application Flexibility
Some herbicides allow application during seeding or overseeding, while others do not. For repair or establishment of St Augustine grass, products safe for use on new growth provide more flexibility for lawn maintenance.
Ease of Use and Dilution
Liquid concentrates that mix with water for spray application provide even coverage and ease of use. Products including measuring tools or being ready-to-use can simplify application for homeowners.
Environmental and Lawn Safety
Look for products that are safe for ornamental plants if you have mixed landscaping. Also, consider herbicides that are low in toxicity and environmentally responsible for residential use.
Volume and Coverage
Choose a size appropriate for your lawn area to avoid waste and ensure complete coverage. Concentrated, larger volume options may offer better value for bigger lawns.
By considering these factors, you can select the best post emergent herbicide to protect and maintain your St Augustine grass lawn, achieving a lush, healthy, and weed-free turf.