Mixing two different types of turfgrass is common for homeowners in the Southern United States, where warm-season varieties like Centipede and St. Augustine dominate lawns. Both grasses are adapted to the region’s climate, but they possess fundamentally different maintenance needs. While Centipede and St. Augustine can grow in the same area, this coexistence is strongly discouraged by professionals. The resulting mixed lawn creates aesthetic and functional problems that make uniform maintenance nearly impossible.
Key Differences in Grass Characteristics
The incompatibility stems from their distinct growth habits and nutritional requirements. St. Augustine grass is aggressive and fast-growing, spreading rapidly via thick surface runners called stolons. Centipede grass, often called the “lazy man’s grass,” is a slower-growing species easily outcompeted by the vigorous St. Augustine.
Soil pH is another dividing factor. Centipede thrives in highly acidic, low-fertility soils, performing best at a pH range of 5.0 to 6.0. St. Augustine prefers a more neutral soil, typically between pH 6.0 and 7.5, and requires significantly more nutrients to maintain density.
Visual differences are immediate, contributing to a mismatched appearance. St. Augustine has a coarse texture with wide, dark green leaf blades that form a dense canopy. Centipede blades are finer, possessing a distinctive apple-green or yellowish-green color.
St. Augustine offers better performance in areas with reduced sunlight. It is one of the most shade-tolerant warm-season grasses, while Centipede requires at least six hours of direct sun to thrive. This difference explains why a mixed lawn may spontaneously occur, with St. Augustine taking over shaded spots where Centipede has thinned.
The Result of Coexistence
When these two species mix, the consequence is a visually non-uniform, patchy lawn. The stark difference in leaf blade width and color prevents the formation of a cohesive, carpet-like turf. The result is a mosaic of dark green, coarse-textured clumps interspersed with lighter, finer-textured sections.
Differing growth rates guarantee that one species will dominate the other, creating uneven terrain. St. Augustine’s aggressive runners and faster growth allow it to quickly cover ground, often smothering the slower-spreading Centipede. This competition causes Centipede to thin out in patches, contributing to the lawn’s irregular density.
A mixed lawn creates a dilemma regarding mowing height. St. Augustine requires a high cut, typically between 2 and 4 inches, to maintain health and density. Centipede must be mowed shorter, ideally between 1 and 2 inches. Mowing high stresses Centipede, while mowing low severely scalps and damages St. Augustine.
The fertilization requirements are contradictory, presenting a major maintenance hurdle. St. Augustine needs a moderate to high amount of nitrogen for vibrant color and fast growth. Applying this level of fertilizer to Centipede can cause “Centipede decline” or “Centipede burn,” weakening the grass and making it susceptible to pests and disease.
Managing or Transitioning a Mixed Lawn
Correctly identifying the dominant grass is the first step in managing a mixed lawn. Look closely at the leaf blades: if they are broad, blunt-tipped, and dark green, St. Augustine is likely the primary species. If the blades are finer, lighter green, and pointed, Centipede may be more prevalent.
The most effective long-term solution is to eliminate the unwanted species to achieve a mono-stand of turf. Selective herbicides can target one grass type over the other, though options are limited and require careful application. If the mixture is widespread, a total lawn renovation—killing all existing turf and laying new sod—may be the most efficient path to uniformity.
If complete renovation is not an immediate option, a homeowner can implement a maintenance strategy that slowly favors the desired species. To promote St. Augustine, maintain a high mowing height of 3 to 4 inches and fertilize with a nitrogen-rich product. This high-input regimen will continuously stress and weaken the Centipede.
To favor Centipede, the opposite approach is necessary, involving a low mowing height of 1.5 inches and minimal nitrogen fertilization. This low-input strategy will gradually weaken the St. Augustine, which relies on a taller canopy and higher nitrogen levels for aggressive growth. Preventing future mixing requires assurance that any new sod or seed is a pure, single species.