How to Kill Black Medic in St. Augustinegrass Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Black Medic 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.
Black medic is an indicator of low-nitrogen, dry, compacted soil. Quinclorac or TZone eliminates the taproot completely.
1. Labeled Safe Herbicides That Kill Black Medic 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 Black Medic
Warning: Common Black Medic Killers That Damage St. Augustinegrass
Many retail herbicides advertised for Black Medic 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 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.
- 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
Apply in late spring when seedlings are young, or in early fall before seed maturation.
Fertilizing lawns with appropriate nitrogen levels helps turf outcompete this legume.
4. Diagnostic Checklist: Confirm It Is Black Medic Before Spraying
- Trifoliate leaves where the center leaflet is on a distinctly longer stalk
- Trailing, square stems radiating from a taproot without rooting at nodes
- Small, bright yellow clover-like flower clusters turning into black, coiled seedpods
Not 100% sure? Use our AI Photo Weed Scanner or review the full Black Medic Botanical Profile.