Cutting grass is a fundamental horticultural practice that directly influences the health and density of a lawn. Regular, correct mowing stimulates the grass plant to produce more lateral shoots, resulting in a thicker turf that naturally crowds out weeds. This practice encourages the plant to allocate resources toward developing a deeper root system, which improves the lawn’s resistance to drought, disease, and environmental stress.
Determining Mowing Frequency Based on Growth
Mowing frequency should not be based on a fixed calendar schedule but rather on the grass’s actual rate of growth. The speed at which your lawn grows is dependent on the species, available moisture, soil nutrients, and temperature. Cool-season grasses, like Kentucky bluegrass and fescue, experience their most vigorous growth during the cooler temperatures of spring and fall. These periods may require mowing as often as every five to seven days to keep up with the rapid vertical expansion of the blades.
Warm-season grasses, such as Bermuda or Zoysia, exhibit their fastest growth during the intense heat of summer and may demand a weekly mowing schedule during this peak time. When temperatures become less favorable, such as during a summer drought, growth slows significantly, and the mowing interval can be extended to ten days or even bi-weekly. The goal is to mow only when the grass has reached the specific height determined by the length you intend to maintain.
The Importance of Optimal Cutting Height
The single most significant factor in maintaining a healthy lawn is adhering to the “One-Third Rule,” which dictates that you should never remove more than one-third of the grass blade’s total height in a single mowing event. This rule is rooted in plant biology, as the grass plant produces its food through photosynthesis, a process that occurs primarily in the leaf blades. Removing too much of the photosynthetic material at once severely shocks the plant, forcing it to use stored energy to rebuild its blades instead of deepening its root system.
When more than one-third of the blade is removed, the plant temporarily halts root growth to conserve energy, making it less resilient to stress. For most common turfgrasses, a final cutting height between 2.5 and 3.5 inches is considered optimal during the active growing season. Maintaining the grass at a greater height provides a greater surface area for photosynthesis and allows the taller blades to shade the soil. This shading helps retain soil moisture, keeps the root zone cooler during high heat, and suppresses the germination of weed seeds.
Seasonal Adjustments to Your Mowing Schedule
The transition of the seasons requires specific adjustments to both the frequency of mowing and the height of the cut to minimize stress on the turf. In the spring, as the grass emerges from dormancy, the frequency increases rapidly as growth accelerates with warming temperatures and ample moisture. During this period of fast growth, you should maintain a moderate cutting height, perhaps at the lower end of the recommended range, to encourage density.
Once summer arrives and temperatures rise, especially during dry spells, grasses can experience heat stress. To combat this, the cutting height should be raised to the top end of the recommended range, often up to 3.5 or 4 inches for cool-season varieties like fescue. This longer blade length provides maximum soil shading and helps insulate the crown of the plant from the drying heat. Mowing frequency often decreases in the heat of summer because many turf varieties naturally slow their growth rate to cope with environmental conditions.
As fall approaches, cool-season grasses enter a second period of rapid growth, often requiring frequent mowing. This is a time for root development before winter dormancy begins. The final few cuts of the season should involve gradually lowering the cutting height until the last mow is approximately 2 to 2.5 inches. This shorter height helps prevent the blades from matting down under winter snow, which can lead to fungal diseases like snow mold.
Best Time of Day for Cutting Grass
Mowing at the correct time of day significantly aids in the plant’s recovery from the stress of being cut. The ideal window is mid-morning, after the morning dew has completely evaporated from the grass blades. Cutting wet grass causes clippings to clump, which can smother the lawn, and increases the risk of tearing the blades instead of making a clean cut. Tearing creates a jagged wound on the plant that is susceptible to disease and infection.
An alternative time is the late afternoon or early evening, generally between 4 PM and 6 PM. At this time, the heat of the day has diminished, reducing the risk of sun-scalding the newly exposed tips of the grass blades. Mowing in the evening allows the grass several hours to begin the healing process before the cooler conditions of night arrive, which can otherwise promote fungal growth on fresh wounds.