The intense heat of summer places considerable stress on turfgrass, fundamentally changing how a lawn must be managed compared to spring or fall. High temperatures disrupt the plant’s processes, depleting stored energy and hindering root growth, especially with insufficient moisture. Mowing practices must shift from encouraging aggressive growth to a strategy focused purely on protection and survival. The objective of summer mowing is to reduce heat stress and maintain the soil’s moisture content. Adjusting mowing height and frequency helps the lawn conserve water and build resilience against prolonged hot, dry conditions.
Establishing Ideal Mowing Height and Frequency
The fundamental concept guiding mowing frequency is the “one-third rule”: never remove more than one-third of the grass blade’s total height in a single session. For example, if the desired cutting height is 3 inches, mow when the grass reaches 4.5 inches. Violating this rule severely stresses the plant, forcing it to expend stored energy on leaf regrowth rather than on root development and heat defense.
This rule dictates a flexible mowing schedule based on the grass’s actual growth rate. In summer, raise the cutting height significantly compared to spring. Taller grass blades create a natural canopy that shades the soil surface, reducing soil temperature and slowing water evaporation. This shading effect keeps the root zone cooler and more hydrated, allowing the grass to maintain deeper roots. For many common grass types, raising the mower deck to 3 to 4 inches is recommended.
Adjusting Mowing Schedules for Grass Type and Climate
The actual frequency of mowing is heavily influenced by the specific type of grass and local climate conditions. Turfgrasses are categorized into cool-season and warm-season varieties, which exhibit vastly different summer behaviors.
Cool-Season Grasses
Cool-season grasses, such as Kentucky Bluegrass and Tall Fescue, thrive between 60°F and 75°F. They naturally slow their growth or enter dormancy when temperatures consistently exceed 85°F. For these varieties, reduce mowing frequency dramatically, often shifting to once every 10 to 14 days, or stopping entirely during extreme heat and drought. If the grass is stressed and not actively growing, forcing a cut increases its susceptibility to disease and heat damage. During this slowdown, maintain a cutting height of 3.5 to 4 inches to maximize soil shading and moisture retention.
Warm-Season Grasses
Warm-season grasses, like Bermuda and Zoysia, are adapted to high summer heat and humidity, with peak growth occurring above 80°F. These actively growing grasses require more frequent mowing, often every 5 to 7 days, to adhere to the one-third rule. While they can be maintained at a lower height (around 2 to 2.5 inches), raising this height slightly during an intense heatwave is recommended for root protection.
Local factors also modify the schedule, regardless of grass type. Areas under dense shade will have slower growth and require less frequent mowing. Conversely, heavy rainfall can trigger growth spurts that necessitate more frequent cutting. Monitor the grass’s growth, rather than adhering strictly to a calendar date, to determine the exact timing of the next cut.
Enhancing Lawn Health Through Proper Mowing Technique
The physical execution of the cut is important for maintaining a healthy summer lawn. A clean cut allows the grass plant to heal quickly, minimizing the open wound that can invite fungal disease and increase water loss. This requires a sharp mower blade; a dull blade tears the grass tips, leaving a ragged appearance vulnerable to pathogens.
Leaving the finely mulched grass clippings on the lawn, known as grass-cycling, is a beneficial practice. These small clippings decompose rapidly, returning essential nutrients and organic matter to the soil, acting as a natural fertilizer, and helping to moderate soil temperature.
The ideal time to mow is mid-morning (8 a.m. to 10 a.m.), after the morning dew has evaporated but before the intense midday heat. Mowing in the late afternoon or evening is also acceptable, but finish early enough to allow the fresh cuts to dry before sunset, reducing the risk of fungal development. Varying the direction of the cut with each mowing prevents the grass blades from leaning over and helps avoid soil compaction. Changing the pattern distributes the mower’s weight more evenly, ensuring a uniform cut and promoting a denser stand of grass.