The summer season presents a unique challenge for maintaining a healthy lawn due to intense sunlight, high temperatures, and potential drought. When grass is subjected to this environmental stress, its survival depends heavily on proper mowing practices. The height at which you cut your lawn is the most significant factor in its resilience against heat and moisture loss. Adjusting your mower deck offers profound protection for the turf during the hottest months.
Recommended Summer Mowing Heights
The general principle for summer lawn care is to maintain the highest cutting height possible for your specific grass type. A consistently higher cut provides instant protection against the harsh sun and allows the grass plant to build energy reserves to withstand heat and dry spells.
A universal guideline in turf management is the “one-third rule,” which states that you should never remove more than one-third of the grass blade’s total height in any single mowing session. For example, if your desired summer height is three inches, mow only when the grass reaches four and a half inches tall. Ignoring this rule can cause severe shock, leading to brown tips and a weakened root system. Following the rule ensures enough green blade remains to support the plant’s metabolic functions and encourage healthy growth.
The Physiological Importance of Taller Grass
Cutting the grass longer during summer directly supports the plant’s biological functions. The greater leaf surface area of a taller blade increases photosynthesis, allowing the plant to produce more energy (carbohydrates) to sustain itself under stress. This improved energy production maintains both the above-ground shoot and the below-ground root system.
Taller grass blades serve a second function by creating a dense canopy that shades the soil surface. This shading effect reduces the soil temperature and minimizes water evaporation from the ground. Keeping the soil cooler protects the grass plant’s crown, the point where the shoot and root meet, which is highly susceptible to heat damage.
The height of the grass blade is also directly linked to the depth of the root system. When the grass is cut short, the plant reduces its root mass to balance the loss of leaf area, resulting in shallower roots. Conversely, a taller cut promotes deeper, more extensive root growth. This deep root system is necessary for the plant to access moisture and nutrients in deeper soil layers during drought conditions. A deep root system is the plant’s primary defense against wilting and dormancy in the summer heat.
Species-Specific Adjustments for Summer Cuts
While a high cut is generally preferred, the ideal height varies significantly between the two main categories of turfgrass: cool-season and warm-season varieties. Cool-season grasses, such as Tall Fescue and Kentucky Bluegrass, prefer a higher setting to cope with summer dormancy. For these types, maintaining a summer mowing height between 3 and 4 inches maximizes shade and moisture retention.
Warm-season grasses, including Bermuda and Zoysia, are adapted to heat and thrive in warmer temperatures, allowing for a slightly lower cut. These grasses typically perform well when maintained between 1 and 2.5 inches, though utilizing the upper end of that range is beneficial during extreme heat. Even for these heat-tolerant varieties, mowing at the tallest acceptable height helps suppress weed germination by blocking sunlight from reaching the soil. The specific measurements ensure the turf is managed in a way that respects its natural growth habit.
Summer Mowing Frequency and Technique
Beyond height adjustment, the technique and timing of summer mowing significantly influence turf health. Ensure that mower blades are kept sharp throughout the season. Dull blades tear the grass instead of making a clean cut, leaving a ragged wound that requires more energy to heal and creates an entry point for diseases and pests.
The best time of day to mow is typically in the late afternoon or early evening, once the peak heat has passed. Mowing during the hottest part of the day places severe stress on the plant, forcing it to expend energy on recovery instead of conserving moisture. It is also beneficial to practice grass cycling, which means leaving the finely chopped clippings on the lawn. These clippings quickly decompose, returning nitrogen and organic matter to the soil, and acting as a light mulch layer to reduce surface moisture evaporation.