How to Kill Yellow Woodsorrel (Oxalis) in St. Augustinegrass Without Hurting Your Lawn
Direct Agronomic Answer
To selectively kill Yellow Woodsorrel (Oxalis) in St. Augustinegrass without damaging your turf, apply Celsius WG (Thiencarbazone-methyl 8.7%, Iodosulfuron-methyl-sodium 1.9%, Dicamba 57.4%), Hi-Yield Atrazine Weed Killer (Atrazine 40.8%) when air temperatures are between 65°F and 95°F.
Standard 2,4-D fails on Oxalis. Systemic Triclopyr or Mesotrione provides excellent foliar and crown kill.
1. Labeled Safe Herbicides That Kill Yellow Woodsorrel (Oxalis) 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 |
| 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 Yellow Woodsorrel (Oxalis)
Warning: Common Yellow Woodsorrel (Oxalis) Killers That Damage St. Augustinegrass
Many retail herbicides advertised for Yellow Woodsorrel (Oxalis) 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 spring or early summer before the explosive cylindrical seed pods mature.
Once seed pods form, slightest contact shoots seeds up to 10 feet into surrounding turf.
4. Diagnostic Checklist: Confirm It Is Yellow Woodsorrel (Oxalis) Before Spraying
- Pale green trifoliate leaves with distinct heart-shaped, deeply notched leaflets
- Leaves fold downward along the center crease at night or in intense heat
- Bright yellow 5-petaled flowers followed by upright, okra-like explosive seed capsules
Not 100% sure? Use our AI Photo Weed Scanner or review the full Yellow Woodsorrel (Oxalis) Botanical Profile.