The frequency of summer lawn mowing should not follow a fixed weekly calendar but must be a dynamic response to the grass’s actual growth rate. Optimal summer lawn care focuses on minimizing stress, which is determined by how much of the leaf blade is removed during any single cut. Understanding the plant’s biology and its species-specific reaction to heat allows homeowners to determine the ideal mowing interval. This approach ensures the turf maintains the energy reserves necessary to survive the heat, humidity, and potential drought of the summer months.
The Biological Basis of Mowing Frequency
The fundamental principle guiding healthy mowing practices is the “One-Third Rule,” which states that you should never remove more than one-third of the grass blade’s total height in a single mowing session. This guideline is rooted in turfgrass biology and protects the plant’s ability to produce food. For example, if you maintain your lawn at a height of three inches, you must mow when the grass reaches four and a half inches.
Removing too much leaf tissue impairs photosynthesis, the process where the plant converts sunlight into energy. Severe cutting, often referred to as scalping, drastically reduces the surface area available for light absorption, effectively starving the plant. Removing more than half of the top growth can cause root growth to stop entirely for a period of days.
This stoppage of root development is a significant problem, as the grass redirects its limited energy to regrow lost leaf material instead of supporting its underground structure. A weakened root system makes the grass vulnerable to environmental pressures like heat, drought, and disease. Adhering to the one-third rule ensures the plant retains enough photosynthetic material to support both top growth and deep, resilient root development. The actual frequency of mowing depends entirely on how quickly the grass grows to 150% of its desired height.
Adjusting Frequency for Grass Types
The necessary mowing frequency in summer is heavily influenced by the specific species of turfgrass in the lawn. Grasses are broadly categorized into cool-season and warm-season types, each having a distinct peak growing season that dictates whether you need to mow more or less often as summer temperatures rise.
Cool-season grasses, including species like Kentucky Bluegrass, Tall Fescue, and Perennial Ryegrass, thrive in the cooler temperatures of spring and fall. These varieties experience a significant slowdown in growth during the sustained heat of mid-summer, especially when temperatures consistently rise above 85 degrees Fahrenheit. Consequently, the mowing interval for these lawns may naturally extend from a weekly schedule to every ten to fourteen days.
Warm-season grasses, such as Bermuda, Zoysia, St. Augustine, and Centipede, behave in the opposite manner, as their growth accelerates in high heat. These species thrive in summer and often require peak maintenance during June, July, and August. In periods of vigorous growth, a warm-season lawn may need to be cut weekly, or even twice a week, to prevent violating the one-third rule. Their high growth rate demands a more frequent schedule to maintain a consistent height.
Adapting Mowing Frequency to Summer Stress
Extreme environmental conditions can override normal growth patterns, demanding an immediate adjustment to the mowing schedule. Prolonged periods of drought or intense heat waves cause the grass plant to enter a protective state known as dormancy. During dormancy, the plant conserves energy by diverting resources away from leaf growth to protect the crown and roots, often resulting in the blades turning a tan or brown color.
If the lawn has visibly stopped growing or is showing signs of browning due to stress, mowing should be reduced dramatically or halted completely. Cutting a dormant lawn removes the plant’s limited energy reserves and can inflict permanent damage. A practical indicator of severe stress is the “footprinting” test, where footprints remain visible after walking across the lawn because the blades lack the turgidity to spring back up.
During periods of high heat, it is beneficial to raise the mower deck to the highest setting for the grass type, often between three and four inches for cool-season varieties. The longer leaf blades created by this higher cut provide essential shade to the soil, which helps to keep the roots cooler and significantly reduces water evaporation. This action helps the turf manage the summer heat, even if the actual mowing frequency is reduced to once every two weeks.