The mowing season is the period when turfgrass is actively growing and requires regular trimming for health and appearance. This timeframe is not a fixed date on a calendar but a dynamic window determined by environmental conditions. Understanding the start and end of this season is crucial for maintaining a dense, resilient lawn, as premature mowing can stress the grass and delayed mowing can lead to fungal issues.
The Environmental Triggers That Define the Start
The initiation of the mowing season is fundamentally governed by soil temperature, not the warmer air temperature. Grass roots begin active nutrient uptake and shoot growth once the soil reaches a certain warmth following winter dormancy. Soil warmth is a more reliable indicator because soil temperatures fluctuate much more slowly than the air, providing a stable signal for biological activity.
Cool-season grasses, such as Kentucky bluegrass and fescues, are the first to wake up, requiring the soil temperature to be consistently in the 50°F to 65°F range for active growth to begin. This range allows the metabolic processes within the grass plant to accelerate, demanding the first cut.
Warm-season grasses, including Bermuda and Zoysia, require substantially higher temperatures for their spring growth surge. These grasses remain dormant until the soil temperature reaches a consistent 65°F to 70°F. Mowing these varieties before they have fully emerged from dormancy can damage the turf and impede their ability to green up fully for the summer season. Monitoring the soil temperature eliminates the guesswork and confirms when root activity has truly resumed.
Regional Variations and Grass Types
Applying these temperature requirements to geography divides the mowing schedule into two primary zones based on the dominant grass type. Cool-season grasses are prevalent in the Northern United States and the transition zones. For these regions, the mowing season typically begins in late March or early April, once the spring thaw allows the soil to warm sufficiently.
This active growth period for cool-season grasses continues through the cooler temperatures of spring and fall. The season generally concludes between late October and mid-November, depending on the severity of the first sustained cold spell.
In the Southern United States, where warm-season grasses thrive, the mowing season starts later, usually in late April or May. This delay is necessary because these grasses need the higher soil temperatures that late spring delivers. Warm-season grasses maintain vigorous growth throughout the summer heat. Their mowing season typically tapers off earlier in the fall, often ending in late September or early October, as night temperatures begin to drop consistently.
Peak Season Frequency and Optimal Height
Once the grass is actively growing, the ongoing maintenance schedule is dictated by the “one-third rule.” This rule suggests that you should never remove more than one-third of the grass blade’s total height in a single mowing session. This practice minimizes shock to the plant, ensuring enough leaf surface remains for efficient photosynthesis to support the root system.
Adhering to the one-third rule often translates to mowing once per week during the peak growth periods of spring and early summer. For example, if you set your cool-season grass height to 3 inches, you should mow when it reaches 4.5 inches tall. During the hottest months, raising the cutting height for both grass types helps shade the soil, promoting deeper root growth and conserving moisture.
For cool-season grasses in summer, raising the height to 3.5 or 4 inches can help prevent heat stress and dormancy. Warm-season grasses, while tolerating lower cuts during peak growth, also benefit from slightly increased height in extreme heat. The frequency may drop during summer drought or excessive heat, as growth naturally slows down, but the one-third rule should guide the timing of the cut.
Signaling the End of the Mowing Season
The mowing season concludes when the grass enters winter dormancy due to sustained cold temperatures. The most reliable sign to stop mowing is when the grass visibly stops growing, which usually corresponds to air temperatures consistently dropping below 50°F for cool-season varieties. For warm-season grasses, growth ceases even sooner, often when temperatures dip below 60°F.
The final cut of the season is a preventative measure that is important for lawn health over winter. This cut should be slightly shorter than the regular cutting height, aiming for a final blade length of 2 to 2.5 inches for cool-season turf. Leaving the grass too long can cause the blades to mat down under snow or persistent moisture, creating an environment for fungal diseases like snow mold to develop.
Mowing the grass to the shorter winter height helps the turf breathe and dry out more effectively, reducing the likelihood of disease development before the lawn goes dormant. This final preparation, timed just before the first hard frost, ensures the grass is resilient enough to survive the winter and promotes a healthy, quick green-up when the environmental triggers signal the start of the next season.