How To Get Rid Of St. Augustine Grass: A Technical Guide To Eradication
Removing St. Augustine grass requires a multi-stage approach combining non-selective systemic herbicides, mechanical excavation, and aggressive soil solarization to neutralize persistent stolons and rhizomes. Because this cultivar is a warm-season perennial that spreads via vigorous above-ground runners, effective eradication demands a consistent treatment window of at least one full growing season to prevent subterranean re-emergence.
Pre-Operation Requirements and Site Assessment
Before initiating removal, you must differentiate St. Augustine (Stenotaphrum secundatum) from other turfgrasses to ensure proper chemical selection. St. Augustine is characterized by broad, coarse leaf blades with rounded tips and a flat, stoloniferous growth habit. Its density often creates a thick thatch layer that acts as a physical barrier against chemical penetration, necessitating pre-treatment preparation.
Essential Equipment and Tools:
High-potency non-selective herbicide containing glyphosate or fluazifop-p-butyl.
A high-pressure compression sprayer or backpack sprayer calibrated for uniform coverage.
A heavy-duty sod cutter for mechanical removal of established mats.
Industrial-grade black plastic sheeting (minimum 4-6 mil thickness) for solarization.
A sharp square-point shovel or mattock for manual stolon extraction.
Personal Protective Equipment (PPE): Nitrile gloves, chemical-resistant boots, eye protection, and long-sleeved work clothing.
Prerequisite Standards and Benchmarks:
Ideal Treatment Window: Active growth phase (late spring to early summer) when temperatures exceed 75 degrees Fahrenheit.
Estimated Duration: 4 to 12 weeks depending on the method chosen and environmental conditions.
Success Metric: The complete cessation of green chlorophyll production and the total desiccation of all stolon nodes.
Comprehensive Eradication Methodology
Step 1: Thatch Reduction and Herbicide Preparation
St. Augustine grass often builds up a dense layer of dead organic matter known as thatch. If this is not addressed, your herbicide will contact the thatch rather than the living tissue. Mow the lawn to the lowest possible setting—typically 1 to 1.5 inches—two days before applying any herbicide. This forces the plant into a stress response and maximizes the surface area of the leaves exposed to chemical treatment.
Warning: Do not apply herbicides on windy days. Glyphosate is a non-selective herbicide that will kill any vegetation it contacts, including surrounding ornamental plants or trees within the drip line.
Step 2: Systemic Chemical Application
Use a systemic herbicide containing glyphosate to ensure the chemical is translocated from the leaf blades down into the stolons and root system. Mix the herbicide according to the manufacturer’s dilution ratios, ensuring a surfactant is included to break the waxy cuticle of the St. Augustine leaf. Apply the herbicide in a fine mist to ensure leaf coverage without runoff.
Pro-Tip: For the best results, use a blue marker dye in your tank mix. This prevents overlapping or missing sections of the lawn, ensuring every square inch of the targeted area receives a lethal dose.
Step 3: Mechanical Extraction and Soil Clearing
Wait 7 to 14 days after the first application. Once the turf has turned brown, use a power sod cutter to remove the top 2 to 3 inches of soil. This depth is critical because St. Augustine runners can penetrate into the topsoil layer. If you are not using a power cutter, manual excavation must be thorough; if a single stolon node remains in contact with moist soil, the grass will eventually propagate.
Step 4: Soil Solarization for Residual Control
After mechanical removal, moisture the soil lightly to encourage the germination of any remaining dormant seeds or fragments. Cover the entire treated area with 4-6 mil black plastic. Seal the edges by burying them in a trench or weighing them down with heavy pavers. Leave this plastic in place for 4 to 6 weeks during the peak of summer. The extreme heat trapped beneath the plastic will pasteurize the top layer of soil, destroying any hidden St. Augustine runners that survived the herbicide and mechanical clearing.
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Comparative Analysis of St. Augustine Removal Methods
| Method | Effectiveness | Labor Intensity | Time to Completion | Best Use Case |
|---|---|---|---|---|
| Chemical Only | Moderate | Low | 4–6 weeks | Sparse, thin patches |
| Mechanical Sod Cutting | High | Medium | 1–2 days | Quick removal for new beds |
| Solarization | Very High | Medium | 6–8 weeks | Total area remediation |
| Manual Digging | Low | Very High | Ongoing | Small, contained gardens |
Troubleshooting Common Field Failures
Root Cause: Incomplete Translocation If the grass regrows after initial spraying, the herbicide likely did not reach the deep root structure. Actionable Fix: Increase the concentration of the surfactant to better penetrate the waxy leaf coating and ensure application occurs while the plant is in its peak metabolic growth phase.
Root Cause: Rhizome Survival Small fragments left in the soil often sprout within weeks of clearing. Actionable Fix: Implement a vigilant monitoring schedule. As soon as a green shoot appears, spot-treat with a concentrated herbicide or manually dig it out, including at least 6 inches of surrounding soil to ensure the root system is captured.
Root Cause: Sub-Optimal Thermal Intensity Solarization failing to kill all material due to lack of sun or loose plastic seals. Actionable Fix: Ensure the plastic is pulled drum-tight and that the edges are buried at least 6 inches deep to prevent heat loss. If the plastic is torn, patch it immediately with high-heat resistant tape.
Frequently Asked Questions
Can I kill St. Augustine grass without using chemicals?
Yes, you can use the sheet mulching or solarization method, but it is significantly more time-consuming. You must cover the area with thick cardboard or heavy plastic for several months to starve the grass of all light, effectively killing the root system through total shading.
How do I stop St. Augustine from creeping into my flower beds?
The most effective way is to install a deep physical landscape border, such as metal or heavy plastic edging, driven at least 6 inches into the ground. St. Augustine stolons travel along the surface, so a well-defined vertical barrier will stop the vast majority of encroachment.
Does tilling kill St. Augustine grass?
No, tilling is counterproductive. Tilling the soil often chops the stolons into smaller, viable segments, each of which can potentially grow into a new plant. This often exacerbates the problem rather than solving it.
How long does it take for St. Augustine to die after spraying?
Using a high-quality glyphosate-based herbicide, you should see initial wilting within 3 to 5 days, with complete brown-out occurring within 10 to 14 days. However, do not assume the roots are dead until you have monitored the area for at least three weeks without signs of regrowth.
Invest in the long-term health of your landscape by ensuring total eradication of unwanted grasses before beginning your new planting project. Consult with local soil experts or regional horticultural extensions if you encounter persistent underground runners despite these rigorous control measures.
