St. Augustine grass (Stenotaphrum secundatum) is a widely planted warm-season turfgrass common across subtropical and tropical regions. It is popular because it creates a thick, carpet-like lawn, particularly in the warm, humid conditions of the southeastern United States and coastal areas. Identifying this species relies on recognizing distinct visual and structural features that give it a unique appearance among common lawn grasses. Understanding these characteristics is important for proper lawn care and for distinguishing it from similar turfgrass varieties.
Leaf Structure and Coloration
The most immediate identifying feature of St. Augustine grass is the size and texture of its leaf blades. It is distinctly coarse-textured, possessing one of the broadest blades among popular warm-season grasses. The blades are flat, relatively thick, and measure between 4 to 10 millimeters wide, often giving the lawn a plush or rugged feel underfoot.
The blade tips are unique, rounded, or blunt, sometimes described as boat-shaped, which contrasts with the pointed tips of many other turf types. Each leaf exhibits a prominent mid-vein running down the center, contributing to a thick, almost rubbery texture. This thickness makes the blades less flexible than those of finer-textured grasses.
The coloration tends to be a medium-green to a distinctive blue-green shade. This characteristic blue-green hue is particularly noticeable when the lawn is well-irrigated and healthy. The leaves are alternately arranged along the stems, contributing to the dense appearance of the turf canopy.
Stolons and Growth Pattern
The overall appearance of a St. Augustine lawn is defined by its lateral growth, which occurs entirely through above-ground runners called stolons. These are stout stems that creep horizontally along the soil surface, forming a dense, intertwined network. As the stolons grow, they root down into the soil at their nodes, establishing new plants and continually expanding the turf area.
The robust nature of these runners is a key physical trait, as they are often visibly compressed or flattened and are coarse to the touch. These compressed stems create a dense matting habit, which is why a mature St. Augustine lawn often feels lush and thick. In some varieties, the base of the stolons near the ground may take on a reddish or purplish tint.
The tightly knit growth resulting from the aggressive spread of these stolons helps suppress weeds by limiting light penetration to the soil. This spreading mechanism allows the grass to establish quickly, filling in bare spots and creating a uniform, carpet-like appearance.
Comparing St. Augustine to Other Warm-Season Grasses
When attempting to identify St. Augustine grass, a comparison with other common warm-season grasses like Bermuda and Zoysia is often the most helpful method.
Bermuda Grass
Bermuda grass (Cynodon dactylon) is visually much finer, possessing a significantly narrower blade texture than the broad, coarse leaves of St. Augustine. While both spread with above-ground stolons, Bermuda also utilizes underground runners called rhizomes, which St. Augustine lacks entirely. This reliance on both growth types gives Bermuda a denser, more interwoven texture, but its finer blades result in a different feel than the rugged St. Augustine. Bermuda requires full sunlight and thins out quickly in shaded areas where St. Augustine maintains better density. The maintenance height of Bermuda is also much lower, typically maintained between 0.5 to 1.5 inches, contrasting with St. Augustine’s taller height of 2 to 4 inches.
Zoysia Grass
Zoysia grass (Zoysia spp.) shares the dense, matting habit of St. Augustine, but its texture is typically softer and more elegant, with blades that are finer or medium-width depending on the specific cultivar. Unlike St. Augustine’s exclusively stoloniferous growth, Zoysia varieties utilize both stolons and rhizomes for spreading, contributing to their impressive density and durability. While Zoysia is often praised for its “manicured” look, St. Augustine maintains its reputation for a more sprawling, coarse texture. Zoysia has a slower growth rate than St. Augustine, leading to less frequent mowing requirements. The visual cue remains the blade width: St. Augustine is consistently coarse, while Zoysia offers a range from fine to medium blades that are generally softer to the touch.