The change in seasons brings a common question for many homeowners: Should the lawn be mowed just before winter? The answer is yes, but the final cut of the year is not like a typical summer trim. This last mowing session is a targeted maintenance task designed to prepare the grass for months of cold and dormancy. Performing this action correctly can significantly influence the health and appearance of the lawn when spring arrives.
Why the Final Cut is Essential
Leaving the grass long as winter approaches encourages disease and pest infestation beneath the snowpack. When long grass blades are matted down by snow and ice, they trap moisture and block air circulation near the soil surface. This lack of airflow and excess moisture provides the perfect habitat for fungal pathogens to thrive.
Reducing the height of the grass before dormancy is a proactive measure against these winter threats. A shorter lawn minimizes the plant material that can mat down and suffocate the turf crown. This action increases air movement at the base of the grass plant, which helps to keep the area drier and less hospitable to fungal growth, particularly snow mold. Long grass also provides shelter and an accessible food source for small winter pests like voles and mice. A shorter lawn removes this protective cover, encouraging these rodents to find shelter elsewhere.
Timing the Last Mow of the Season
The correct time for the final mow is determined by the grass plant’s transition into winter dormancy, not a specific date. Grass growth slows substantially once consistent daytime air temperatures drop below 50°F (10°C). Once soil temperatures fall below this point, growth virtually ceases. This temperature drop signals that the plant is moving its energy reserves from the leaves to the roots and crown for winter survival.
The ideal timing is when the grass is still growing enough to recover slightly from the cut, but late enough that no significant regrowth occurs before the first hard freeze. Mowing too early risks the grass growing back too long before snow falls, while mowing too late, after the first hard frost, can stress the frozen blades. Monitoring local forecasts for the first predicted hard frost and watching for the slowdown in growth are more reliable cues than arbitrary dates.
The Optimal Height for Winter Grass
The goal of the final cut is to achieve a specific height that balances protection and vulnerability. For most cool-season grasses, the optimal height is between 2 and 2.5 inches. This height is short enough to prevent the blades from bending over and matting under the weight of snow, which is the primary cause of snow mold formation.
Cutting the grass too high, above 3 inches, leaves excessive leaf tissue that traps moisture and provides cover for pests. Conversely, cutting the grass too low, often called “scalping,” is also detrimental because it removes too much leaf surface and can damage the plant’s crown. The crown, located just above the soil line, is where the grass stores the carbohydrates needed to survive winter. Exposing it increases the risk of winter injury and desiccation. The recommended height minimizes fungal and pest risk while preserving the plant’s stored energy.
Avoiding Common Winter Lawn Hazards
Ignoring proper preparation can lead to several distinct hazards that damage the lawn during winter.
Snow Mold
Snow mold is a fungal disease that appears as circular, matted patches of gray or pinkish-white growth as the snow melts. This condition is directly related to long grass trapped beneath the snow, which creates an airless, moist environment conducive to fungal proliferation.
Pest Damage
Damage caused by voles and mice is another common problem. They use long grass as a covered runway system to tunnel and feed on the grass blades and crowns under the snow. The damage appears in the spring as winding trails of dead, chewed-down grass once the snow melts.
Winter Desiccation
Extremely short grass is more susceptible to winter desiccation, which is the drying out of the plant tissue. This occurs when winter winds and sun draw moisture from the exposed blades faster than the frozen roots can replace it, resulting in brown, straw-like patches.