Preparing a lawn for winter dormancy involves a final cut, often called a winterization cut, which confuses many homeowners. Homeowners often debate whether to leave the grass long for insulation or cut it extremely short. Getting this last mow right significantly impacts the lawn’s health and appearance when spring arrives. The optimal height is a balance, as cutting too high or too low introduces specific risks that can severely impact the turf’s survival over winter.
The Dangers of Scalping Your Lawn
Cutting the grass excessively low, or scalping, just before winter is detrimental to the plant’s health and ability to survive dormancy. The grass blade is the primary site of photosynthesis, producing and storing the carbohydrates needed for winter survival. Cutting too much green tissue reduces the plant’s ability to store adequate energy reserves in its roots before growth stops.
This aggressive cut stresses the root system, forcing the plant to expend stored energy to regrow leaf tissue instead of directing resources toward cold tolerance. When the turf is scalped, the crown—the growth point just above the soil line—is left vulnerable to the harsh winter environment. Exposure to repeated freeze-thaw cycles and cold, drying winds (desiccation) can damage or kill this sensitive area.
Short grass offers minimal ground cover, increasing vulnerability to weed germination. Bare patches of soil created by a severe cut invite winter annual weeds to establish themselves without competition. A scalped lawn is weakened and will struggle to recover when the next growing season begins.
Why Excessive Height Invites Winter Damage
Leaving the grass too long before winter dormancy creates problems by fostering conditions conducive to disease and pest activity. When grass blades are excessively tall, they mat down under snow cover, trapping moisture and creating a dense, damp environment at the soil surface. This warm, humid microclimate is an ideal breeding ground for cold-weather fungal pathogens.
The most common consequence of overly long grass under snow is the development of snow mold, which appears as pink or gray patches when the snow melts in spring. This disease can suffocate the turf and delay spring green-up, requiring significant repair. The matted grass also blocks sunlight and air circulation, potentially leading to widespread turf thinning.
Excessive grass height also provides sheltered habitat for small rodents, such as voles, to survive and feed throughout the winter. These pests create visible trails and runways beneath the snow, feeding on the grass blades and crowns. This results in significant damage apparent in the spring thaw. Mowing to a reasonable height removes this protective layer, making the area less hospitable for these overwintering animals.
The Recommended Final Cut Height and Timing
The optimal approach is to find a moderate height that avoids the risks of both scalping and excessive length. For most cool-season grasses, this height is typically 2 to 2.5 inches. This length is short enough to prevent matting and discourage snow mold, yet long enough to shield the crown from extreme cold and allow for sufficient carbohydrate storage in the roots.
The timing of this final cut is determined by the grass’s growth rate, not a specific calendar date, and should occur just before the grass enters dormancy. Mowing must continue as long as the grass is actively growing, which typically ceases when daytime air temperatures consistently drop below 50 degrees Fahrenheit. The final mow is generally completed just before the first hard freeze, ensuring the grass is at its winter height before the ground freezes solid.
It is important to gradually reduce the mowing height over the final few cuts of the season, rather than dropping the height drastically in a single pass. If the lawn was maintained at 3.5 inches during the fall, the height should be lowered incrementally by no more than one-half inch per mowing session until the target 2 to 2.5-inch height is achieved. This gradual reduction minimizes shock and stress as the plant prepares for winter rest.