Whether you can cut grass in the winter depends entirely on your specific climate and the physiological state of your lawn. In regions with consistently frozen ground and heavy snow cover, the grass is truly dormant and requires no attention from a mower. However, in areas with milder winters or periods of temporary warmth, the grass may continue to grow slowly, necessitating occasional cutting to maintain turf health. Understanding the biological processes that govern this growth is the first step in making the correct decision. The need to mow is dictated not by the calendar, but by the plant’s reaction to soil temperatures and the resulting growth rate.
Understanding Grass Dormancy
The state of dormancy determines whether grass needs cutting. For cool-season grasses, such as Kentucky bluegrass and fescue, growth slows significantly when soil temperatures dip below 45 degrees Fahrenheit. While these grasses may remain green, their metabolic activity is greatly reduced, causing them to enter a semi-dormant state where mowing is rarely required.
Warm-season grasses, including Bermuda and Zoysia, react more dramatically to cold. They enter a full dormancy when soil temperatures drop below 50 degrees Fahrenheit, causing the grass to turn brown completely. All visible growth ceases. This shutdown conserves energy reserves in the crown and roots, ensuring the plant can survive harsh conditions and resume growth when temperatures warm again.
When Mowing During Winter Is Necessary
In many regions, winter often includes intermittent mild spells where temperatures temporarily rise above the dormancy threshold. If the soil temperature rises sufficiently, the grass will exhibit slow but visible growth, and this is when a winter cut becomes necessary. Allowing the grass to become too long during these mild periods can promote matting, particularly when snow eventually falls and compresses the turf.
This matting creates an ideal environment for fungal diseases, most notably snow mold. Snow mold thrives in cool, moist, and poorly ventilated conditions under snow cover. If the grass has grown substantially, a light trim should be performed to prevent the blades from collapsing and trapping excessive moisture. You must only mow when the grass is completely dry and the ground is not frozen, as cutting frosted blades or driving a mower over frozen soil can cause significant damage to the turf crowns and root structure.
The Importance of Optimal Winter Height
Maintaining a specific height for the final cuts of the season and during any necessary winter trims supports the health of the plant. A height between 2 and 3 inches is recommended for cool-season grasses entering winter dormancy. This range is short enough to prevent the grass blades from bending over and creating the dense, moist environment that encourages snow mold development.
Cutting the grass too short can expose the vulnerable crown to harsh cold and desiccating winds, depleting the stored carbohydrates needed to survive the winter. Conversely, leaving the grass too long, over 3 inches, increases the risk of snow mold and provides shelter for pests like voles. For warm-season grasses, the optimal final height is slightly shorter, around 1.5 to 2.5 inches.