St. Augustine grass (Stenotaphrum secundatum) is a warm-season turfgrass frequently chosen for its deep green color and tolerance to heat and shade. Its dense growth habit is facilitated by aggressive, thick surface runners called stolons. These stolons creep rapidly across the ground, rooting at the nodes to form a thick thatch layer. Removing the grass completely requires a comprehensive, multi-step approach that accounts for this aggressive growth pattern to ensure all plant material is killed and prevent rapid regrowth.
Non-Chemical Eradication Strategies
Manual removal and solarization offer effective, non-chemical pathways, though they are labor-intensive or time-consuming. Manual removal involves physically digging out the turf, which is best achieved when the soil is moist to a depth of several inches. Using a sharp spade or a rented sod cutter to slice the turf into manageable strips helps isolate the shallow root system. The thick stolons and dense mat of roots must be entirely removed, as any remaining fragment can quickly re-establish itself.
A passive approach is solarization, which uses sheeting to deprive the grass of sunlight and increase the temperature to lethal levels. For solarization, clear plastic sheeting is laid over the area after it is mowed low and watered to encourage active growth. The clear plastic traps solar radiation, raising the soil temperature high enough to kill the grass tissue and seeds beneath. This method is most effective during the hottest part of the summer and requires the plastic to remain in place for six to eight weeks.
Alternatively, smothering uses thick, opaque black plastic or layers of cardboard and mulch to completely block out sunlight and air. This method, often called sheet mulching, starves the grass of the energy it needs for photosynthesis, causing it to die back slowly. Smothering takes significantly longer than solarization, sometimes requiring several months for the entire root system and stolons to decompose. Once the grass is dead, the decomposed material can be tilled into the soil, adding organic matter.
Chemical Control Options
Chemical eradication offers the quickest path to clearing a large area, requiring a non-selective herbicide due to the grass’s resilience and the goal of total removal. Non-selective herbicides, most commonly containing glyphosate, kill nearly all vegetation by disrupting an essential metabolic pathway. Since the chemical must be translocated to the roots, application must occur when the grass is actively growing, typically in warm weather during late spring or summer.
Before application, mow the grass and allow a few days for new leaf tissue to emerge, maximizing the herbicide’s absorption surface area. The product must be mixed precisely according to the label’s directions. Safety is paramount, requiring personal protective equipment and careful attention to weather conditions to avoid wind drift, which could damage desirable nearby plants.
The systemic nature of glyphosate means results are not immediate; it can take two weeks or more for the grass to fully die back and turn brown. Complete eradication often requires a second application of the non-selective herbicide ten to fourteen days after the initial treatment. It is also important to avoid watering or disturbing the treated area for at least seven days following application to allow the chemical sufficient time to move throughout the plant tissue and reach the stolons and roots.
Post-Removal Management and Prevention
Once the St. Augustine grass is killed and the dead material removed, the area requires attention to prepare the soil for new plantings and prevent future invasions. The removal process leaves behind a dense layer of thatch and thick stolons, which should be thoroughly raked out and disposed of. Tilling the soil afterward helps break up compaction, incorporate remaining organic matter, and improve aeration for the establishment of new roots.
The tilled area should be leveled and amended with new topsoil or organic materials like composted manure to enrich the nutrient profile. Consistent monitoring is necessary, particularly during the next growing season, to catch any regrowth from missed stolon fragments. Any new shoots that emerge should be immediately spot-treated with a non-selective herbicide or manually dug out to prevent re-establishment.
To prevent future encroachment from neighboring St. Augustine lawns, installing physical barriers is highly recommended. Deep, continuous edging or root barriers placed along property lines can block the aggressive stolons from creeping into the cleared area. The use of a pre-emergent herbicide can also be considered to prevent the germination of stray seeds or weeds, but ensure it does not interfere with the establishment of new sod or seed.