How to Kill Dollarweed (Pennywort) in St. Augustinegrass Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Dollarweed (Pennywort) in St. Augustinegrass without damaging your turf, apply Celsius WG (Thiencarbazone-methyl 8.7%, Iodosulfuron-methyl-sodium 1.9%, Dicamba 57.4%), Image Kills Nutsedge (Imazaquin 3.3%) when air temperatures are between 65°F and 95°F.
For Bermudagrass and cool-season turf, 2,4-D or SpeedZone is effective. Reducing irrigation frequency is vital as Dollarweed indicates waterlogged conditions.
1. Labeled Safe Herbicides That Kill Dollarweed (Pennywort) 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 |
| Image Kills Nutsedge EPA Reg. 228-719 |
Imazaquin 3.3% Group 2 (ALS Inhibitor / Imidazolinone) |
65°F – 90°F Rainfast: 6h |
Ready-to-mix liquid formulation contains surfactant; additional NIS is not required for standard broadcast or spot treatments. | Check Price at DoMyOwn View on Amazon |
| Hi-Yield Atrazine Weed Killer EPA Reg. 34911-15-7401 |
Atrazine 40.8% Group 5 (Photosystem II Inhibitor / Triazine) |
50°F – 85°F Rainfast: 6h |
Do NOT add surfactant when spraying actively growing St. Augustine or Centipede above 80°F to avoid foliar yellowing. Irrigate lightly within 48 hours for root uptake. | Check Price at DoMyOwn View on Amazon |
2. What NOT to Spray on St. Augustinegrass When Treating Dollarweed (Pennywort)
Warning: Common Dollarweed (Pennywort) Killers That Damage St. Augustinegrass
Many retail herbicides advertised for Dollarweed (Pennywort) are formulated for different turf zones and will severely injure St. Augustinegrass:
- AVOID Drive XLR8 (Quinclorac 18.92%): Rated 'avoid' 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.
3. Optimal Seasonal Timing & Temperature Thresholds
Spray in spring or fall when Dollarweed is actively sending up new circular leaves.
Sequential applications 2 to 3 weeks apart are required to eradicate deep underground rhizomes.
4. Diagnostic Checklist: Confirm It Is Dollarweed (Pennywort) Before Spraying
- Bright green, circular silver-dollar-shaped leaves with scalloped margins
- Petiole attaches directly in the center of the leaf undersurface (peltate umbrella-like)
- Spreading fleshy rhizomes and tubers thriving in over-irrigated waterlogged soil
Not 100% sure? Use our AI Photo Weed Scanner or review the full Dollarweed (Pennywort) Botanical Profile.