Preparing a lawn for winter dormancy requires careful consideration of the final cut before growth ceases. The height of this last mowing directly influences the turf’s survival through the cold months and its vigor in the following spring. Finding the perfect balance between too long and too short protects the grass from environmental stress, disease, and pests. The goal is to set the lawn up to store sufficient energy while minimizing risks associated with snow cover and harsh temperatures.
Determining the Ideal Final Height
The optimal height for the final cut of the season is a moderate length, generally falling between 2 and 2.5 inches for most cool-season grasses. This length is short enough to prevent matting but long enough to shield the plant’s crown and maintain energy reserves. Achieving this measurement should be a gradual process over the last few weeks of mowing, known as the “step-down” approach.
Instead of a single drastic cut, the mower deck should be lowered one notch at a time. Ensure that no more than one-third of the grass blade is removed during any single mowing session. This technique minimizes shock, allowing the grass to acclimate to the lower height while still actively photosynthesizing. A final height around 2 inches provides a protective layer over the soil and the grass crown, keeping the leaf blades upright and exposed to air circulation.
The Dangers of Leaving Grass Too Long
Allowing the grass to remain excessively long—typically over 3 inches—when it enters dormancy creates an environment highly conducive to fungal diseases. The primary concern is the development of “snow mold,” which occurs in two main forms: gray snow mold and pink snow mold. These fungi flourish in the cold, wet, and dark conditions that exist beneath a blanket of snow.
When long grass blades are matted down by heavy snow or moisture, air circulation is severely restricted, creating an anaerobic layer near the soil surface. This dense, moist environment is the perfect breeding ground for fungal pathogens that actively decompose the dormant grass tissue. The resulting damage appears as circular, matted patches that can significantly delay spring green-up. Furthermore, long, dense turf provides excellent shelter for overwintering pests, such as voles. Voles can cause significant damage by tunneling beneath the snow and feeding on the grass crowns.
Why Cutting Too Short Is Detrimental
Conversely, cutting the lawn too short, often referred to as scalping, is detrimental because it directly damages the grass plant’s capacity to survive the winter. The grass blade is the plant’s solar panel, responsible for photosynthesis, which creates and stores the necessary carbohydrates for dormancy. Removing too much leaf tissue drastically limits the plant’s ability to store the energy reserves needed to endure the cold and initiate spring growth.
Scalping the lawn also exposes the crown, the growth point of the grass plant located just above the soil line, to harsh winter elements. Without sufficient blade length for insulation, the crown becomes vulnerable to desiccation from cold, drying winds and damage from freeze-thaw cycles. This exposure can lead to winter injury, weakening the plant and causing it to spend the spring recovering from shock. A lawn that is cut too low will have fewer stored resources and a damaged crown, making it susceptible to thinning and weed invasion.