How to Kill Black Medic in Tall Fescue Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Black Medic in Tall Fescue without damaging your turf, apply Tenacity (Mesotrione 40%), Drive XLR8 (Quinclorac 18.92%) when air temperatures are between 55°F and 85°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 Tall Fescue
| Recommended Product | Active Ingredient & Group | Application Temp (°F) | Surfactant & Mixing Protocol | Where to Buy |
|---|---|---|---|---|
| Tenacity EPA Reg. 100-1267 |
Mesotrione 40% Group 27 (HPPD Inhibitor) |
55°F – 85°F Rainfast: 6h |
Always apply with Non-Ionic Surfactant (NIS) at 1 tsp (5 mL) per gallon of water for post-emergent applications. Causes temporary white bleaching on susceptible weeds and turf tips. | Check Price at DoMyOwn View on Amazon |
| Drive XLR8 EPA Reg. 7969-272 |
Quinclorac 18.92% Group 4 (Synthetic Auxin / Quinoline Carboxylic Acid) |
60°F – 85°F Rainfast: 1h |
Requires Methylated Seed Oil (MSO) surfactant at 1.5 tbsp (0.75 fl oz) per gallon of water for effective cuticle penetration on multi-tiller crabgrass. | Check Price at DoMyOwn View on Amazon |
| SpeedZone Lawn Weed Killer EPA Reg. 2217-833 |
2,4-D 28.57%, Mecoprop-p 5.88%, Dicamba 1.71%, Carfentrazone-ethyl 0.62% Group 4 + Group 14 (Synthetic Auxins + PPO Inhibitor) |
50°F – 85°F Rainfast: 3h |
Do NOT add surfactant. Adding NIS or MSO increases ester volatility and causes severe contact burn on desirable cool-season turf. | Check Price at DoMyOwn View on Amazon |
| TZone SE EPA Reg. 2217-920 |
Triclopyr 7.72%, 2,4-D 29.36%, Dicamba 2.22%, Sulfentrazone 0.66% Group 4 + Group 14 (Pyridine Auxin + Phenoxy + PPO Inhibitor) |
50°F – 80°F Rainfast: 3h |
Do NOT mix with surfactant when temperatures exceed 75°F. In cool spring or fall conditions (55°F–70°F), 0.5 tsp NIS per gallon improves waxy leaf penetration on Wild Violet. | Check Price at DoMyOwn View on Amazon |
2. What NOT to Spray on Tall Fescue When Treating Black Medic
Warning: Common Black Medic Killers That Damage Tall Fescue
Many retail herbicides advertised for Black Medic are formulated for different turf zones and will severely injure Tall Fescue:
- AVOID Celsius WG (Thiencarbazone-methyl 8.7%, Iodosulfuron-methyl-sodium 1.9%, Dicamba 57.4%): Rated 'avoid' on Tall Fescue — 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.