Organic Weed Control Strategies for St. Augustine Lawns

Why Weeds Invade St. Augustine

Clover and broadleaf weeds indicate underlying issues: low nitrogen, compacted soil, improper mowing, or insufficient watering. Healthy, dense St. Augustine naturally crowds out weeds.

Cultural Practices First (Organic Foundation)

• Fertilize monthly with organic lawn fertilizer (e.g., 8-2-4) during active growth (April–September).
• Water deeply twice weekly (1 hour per zone) rather than daily light sprinkling.
• Mow at 3–3.5 inches frequently—never below 2.5 inches.
• Sharpen mower blades monthly for clean cuts.

Vinegar Caution

Vinegar (acetic acid) kills weeds by desiccation but also damages St. Augustine. Use only for spot-treatment on driveways, not lawn.

Transition Strategy for Heavy Weed Pressure

1. Apply selective broadleaf herbicide (e.g., Scott's Turf Builder Weed & Feed 2+2) to wet lawn; wait 48 hours before watering.
2. Or use liquid Ortho Weed-B-Gon (hose-end) on calm day, 50–85°F.
3. Keep pets off 48 hours after watering in.
4. Once weeds controlled (2–3 weeks), switch fully to organic program above.

Long-Term Organic Weed Prevention

Dense grass + healthy soil = few weeds. Annual aeration, compost topdressing (¼ inch), and corn gluten meal in spring maintain the advantage.