How to Kill Broadleaf Plantain in St. Augustinegrass Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Broadleaf Plantain in St. Augustinegrass without damaging your turf, apply Celsius WG (Thiencarbazone-methyl 8.7%, Iodosulfuron-methyl-sodium 1.9%, Dicamba 57.4%) when air temperatures are between 65°F and 95°F.
Broadleaf plantain translocates synthetic auxins rapidly into its fibrous root system. For warm-season lawns like St. Augustine and Centipede, Celsius WG provides safe control.
1. Labeled Safe Herbicides That Kill Broadleaf Plantain in St. Augustinegrass
| Recommended Product | Active Ingredient & Group | Application Temp (°F) | Surfactant & Mixing Protocol | Where to Buy |
|---|---|---|---|---|
| Celsius WG EPA Reg. 432-1507 |
Thiencarbazone-methyl 8.7%, Iodosulfuron-methyl-sodium 1.9%, Dicamba 57.4% Group 2 + Group 4 (ALS Inhibitors + Benzoic Acid Auxin) |
65°F – 95°F Rainfast: 4h |
Apply with Non-Ionic Surfactant (NIS) at 1 tsp per gallon of water. Specifically engineered not to stunt warm-season turf during summer heat up to 95°F. | Check Price at DoMyOwn View on Amazon |
2. What NOT to Spray on St. Augustinegrass When Treating Broadleaf Plantain
Warning: Common Broadleaf Plantain Killers That Damage St. Augustinegrass
Many retail herbicides advertised for Broadleaf Plantain are formulated for different turf zones and will severely injure St. Augustinegrass:
- AVOID Tenacity (Mesotrione 40%): Rated 'sod_production_only' on St. Augustinegrass — high risk of turf phytotoxicity or stunting.
- AVOID SpeedZone Lawn Weed Killer (2,4-D 28.57%, Mecoprop-p 5.88%, Dicamba 1.71%, Carfentrazone-ethyl 0.62%): Rated 'avoid' on St. Augustinegrass — high risk of turf phytotoxicity or stunting.
- AVOID TZone SE (Triclopyr 7.72%, 2,4-D 29.36%, Dicamba 2.22%, Sulfentrazone 0.66%): Rated 'avoid' on St. Augustinegrass — high risk of turf phytotoxicity or stunting.
3. Optimal Seasonal Timing & Temperature Thresholds
Spray in early fall (September to October) when plants are actively moving carbohydrates to root reserves.
Spring applications work well before flower spikes emerge. Aerating compacted soil prevents plantain re-establishment.
4. Diagnostic Checklist: Confirm It Is Broadleaf Plantain Before Spraying
- Large, oval to egg-shaped, wavy-margined leaves with 3 to 5 prominent parallel veins
- Dense basal rosette hugging the ground tightly
- Erect, leafless flower stalks with dense, cylinder-like spikes of tiny seeds
Not 100% sure? Use our AI Photo Weed Scanner or review the full Broadleaf Plantain Botanical Profile.