Preparing a lawn for winter dormancy requires a final, specific mowing height that differs from routine summer maintenance. This last cut is a calculated step to ensure the grass survives the cold months and rebounds healthily in the spring. The goal is to prepare the turf for low or no growth while minimizing winter-related diseases and physical damage. Achieving the correct height optimizes the grass’s ability to store energy and maintain air circulation beneath snow cover.
The Ideal Final Mowing Height
For most common cool-season turf varieties, such as Kentucky bluegrass and fescues, the ideal final mowing height for winter is between 2 and 2.5 inches. This measurement acts as a “sweet spot” as the grass enters dormancy. Maintaining this height ensures the blades are short enough to prevent them from bending over and matting down under the weight of snow and ice.
This height leaves sufficient leaf surface area for the plant to continue minimal photosynthesis during warmer autumn days. The resulting energy allows the grass to store necessary carbohydrates in the crown and root system for survival and spring growth. Cutting within this range provides a protective layer that helps insulate the grass crown, the sensitive growth point, against harsh winter elements.
Consequences of Cutting Too Low
Cutting the grass significantly below the recommended 2-inch height introduces several risks. The primary concern is the exposure of the sensitive crown to severe cold and drying winds. This exposure can lead to dehydration and physical damage, potentially killing the plant’s growth center before spring.
Cutting too low also compromises the plant’s ability to store necessary energy reserves. Removing too much leaf tissue limits late-season photosynthesis, which is how carbohydrates are built and stored in the roots and crown. A severely shortened lawn enters winter depleted of energy, making it slower and weaker to green up in the spring.
Preventing Winter Disease and Matting
Leaving the grass too long for winter, typically above 3 inches, increases the risk of fungal diseases, particularly snow mold. Longer blades fold over and mat when pressed down by snow, creating a dense layer that traps moisture and heat. This creates an insulated, humid microclimate on the soil surface, which is a breeding ground for fungal pathogens.
A shorter cut (2 to 2.5 inches) reduces the plant material available to mat down and limits the surface area where moisture can be retained. This improved air circulation at the base of the turf minimizes the conditions necessary for snow mold development, helping the lawn emerge healthier in the spring.
Timing the Final Cut
The timing of the final mowing is determined by temperature, not a specific date. The last cut should be performed just before the grass enters full dormancy and stops actively growing. This slowdown usually occurs when soil temperatures consistently drop below 50 degrees Fahrenheit.
Continue mowing regularly through the fall until this growth cessation is observed. The final cut should happen shortly before the first permanent snowfall, ensuring the grass is at its winter height when the ground freezes and snow cover arrives. This timing prevents the grass from growing too tall, which would increase the risk of matting and disease under the snowpack.