How to Kill Common Lambsquarters in Tall Fescue Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Common Lambsquarters in Tall Fescue without damaging your turf, apply Tenacity (Mesotrione 40%), SpeedZone Lawn Weed Killer (2,4-D 28.57%, Mecoprop-p 5.88%, Dicamba 1.71%, Carfentrazone-ethyl 0.62%) when air temperatures are between 55°F and 85°F.
Regular mowing easily prevents Lambsquarters from reaching upright maturity in maintained turf.
1. Labeled Safe Herbicides That Kill Common Lambsquarters 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 |
| 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 |
| Barricade 4FL (Prodiamine 65 WDG) EPA Reg. 100-1139 |
Prodiamine 40.7% (or 65% WDG) Group 3 (Microtubule Assembly Inhibitor / Dinitroaniline) |
45°F – 90°F Rainfast: 0h |
Pre-emergent soil barrier: do NOT use foliar surfactant. Must be watered in with 0.5 inches of irrigation or rainfall within 14 days of application to activate. | Check Price at DoMyOwn View on Amazon |
3. Optimal Seasonal Timing & Temperature Thresholds
Spray in late spring when seedlings are 2 to 4 inches tall.
The mealy coating becomes thicker with age; adding surfactant enhances foliar absorption.
4. Diagnostic Checklist: Confirm It Is Common Lambsquarters Before Spraying
- Erect upright growth with triangular to diamond-shaped wavy leaves
- Whitish, mealy or powdery coating on younger leaves and shoot tips
- Dense, spike-like clusters of tiny inconspicuous green flowers at stem ends
Not 100% sure? Use our AI Photo Weed Scanner or review the full Common Lambsquarters Botanical Profile.