St. Augustine grass (Stenotaphrum secundatum) is a popular, coarse-bladed, warm-season turf common across the Southern United States. It relies heavily on consistent and proper maintenance. Regular mowing is the single most important factor for regulating the turf’s density and preventing weed intrusion. Understanding the correct frequency and technique is the first step toward a healthy St. Augustine lawn.
Determining Optimal Mowing Frequency
The frequency with which St. Augustine grass should be cut is not fixed to a calendar date but is instead determined by its current growth rate. During the peak growing season, which generally aligns with the hot, humid summer months, growth accelerates rapidly due to favorable temperatures and moisture. To prevent excessive stress, the “one-third rule” must be strictly followed.
This rule dictates that no more than one-third of the total grass blade height should be removed during any single mowing session. For example, if the target height is four inches, the grass must be mowed before it reaches six inches tall. Adhering to this limit during the summer often means mowing every five to seven days to keep up with the vigorous growth. Removing too much leaf tissue at once can “scalp” the lawn, causing significant stress and leaving the underlying runners vulnerable to damage and sun exposure.
Setting the Correct Blade Height
St. Augustine grass requires a tall cut compared to other turf varieties to thrive in warm climates. The recommended range for a healthy lawn is between 2.5 and 4 inches, though aiming for the higher end is often suggested. This taller blade height serves a dual purpose by shading the delicate stolons, or runners, that spread horizontally across the soil surface. These runners are responsible for the grass’s lateral growth and density.
The increased leaf surface area also promotes deeper root growth, making the turf more resilient to drought and high temperatures. Cutting the grass too short exposes the soil and the runners to intense sunlight, which can lead to thinning, browning, and increased susceptibility to pests and weeds. In areas of partial shade, maintaining the height at the upper limit, between 3.5 and 4 inches, helps maximize the leaf area available for photosynthesis.
Adjusting Mowing Schedules Seasonally
Mowing frequency changes naturally as temperatures fluctuate throughout the year. The highest frequency occurs during the summer when the combination of heat and moisture drives maximum growth, requiring weekly or near-weekly cuts to obey the one-third rule. As the shoulder seasons of spring and fall arrive, growth slows down due to cooler temperatures and shorter daylight hours. This reduced growth rate means the mowing frequency can be decreased, often to every 10 to 14 days.
In late fall, as the grass prepares for winter dormancy, growth will slow significantly or stop entirely in cooler regions. Mowing may be reduced to once a month or cease altogether, depending on the local climate. Where St. Augustine grass goes fully dormant, the primary reason for a winter cut is to clean up debris, not to regulate growth. In preparation for winter, raising the mowing height by about half an inch in the fall provides extra insulation to the crowns and roots.
Essential Mowing Techniques
Beyond frequency and height, the specific techniques used during mowing directly impact the turf’s health and appearance. Keeping the mower blades consistently sharp is a fundamental practice for St. Augustine grass, which has wide, coarse blades. A dull blade rips and shreds the leaves instead of making a clean cut, leaving ragged edges that turn brown and increase the plant’s vulnerability to disease and moisture loss. Sharpening the blade at least once per season is recommended to ensure a clean shear.
Leaving the grass clippings on the lawn, a process known as mulching or grass-cycling, is another beneficial practice. Provided the one-third rule is followed, these finely chopped clippings decompose quickly and return valuable nitrogen and other nutrients back into the soil. Varying the mowing pattern with each cut is important to prevent the turf from developing a grain or leaning in one direction. Changing the direction helps reduce soil compaction and avoids creating ruts that can harm the stolon system.