Stopping mowing as temperatures drop is necessary to protect the health and long-term survival of the turf. Grass reacts to cold by preparing for physiological dormancy, conserving energy to endure winter conditions. Mowing during this transition can damage the grass, limiting its ability to store the carbohydrates needed for spring recovery. Lawn owners must recognize the natural signals the grass gives when it is time to put the mower away.
Identifying the Physiological Stop Point
The most reliable indicator that the mowing season is ending is the consistent drop in temperature that slows the grass plant’s internal processes. Most turfgrass species significantly reduce their growth rate when temperatures fall consistently between 50°F and 55°F (10°C to 13°C). This is the point where the plant shifts its focus from producing green leaf tissue to storing energy reserves in its crown and roots.
Mowing the lawn while it enters this semi-dormant state forces the plant to divert stored energy toward healing the cut blades. This unexpected demand depletes the carbohydrate supply needed to survive the cold season and initiate spring growth. Continuing to mow below this threshold stresses the grass, leaving it weakened and more susceptible to winter injury and disease.
The Physical Hazard of Mowing Frozen Ground
Even before the physiological stop point is reached, physical activity on a lawn covered in frost or frozen ground can cause immediate damage. When the temperature drops to the freezing point of 32°F (0°C), the water inside the grass blades freezes and expands, making the normally flexible leaf tissue extremely brittle.
Mowing or walking on frosted grass crushes and shatters the frozen plant cells, leading to visible cellular breakdown. The damaged areas appear as white or brown tracks that persist until new growth resumes in the spring. If the soil is frozen, running machinery over the turf can cause a shearing effect that damages the root crowns. Wait until the frost has completely melted and the blades have regained their flexibility before any activity on the lawn.
How Grass Type Determines Cold Mowing Limits
The precise timing for the final cut depends significantly on whether the lawn consists of cool-season or warm-season grasses. Cool-season varieties, such as Kentucky Bluegrass, Fescue, and Ryegrass, thrive in cooler temperatures and may continue slow growth into late fall. For these grasses, occasional mowing may still be necessary until the temperature consistently drops below 40°F (4°C).
Warm-season grasses, including Bermuda and Zoysia, are less tolerant of cold and enter a complete, brown dormancy much earlier. Their growth slows or stops when the temperature falls below 55°F (13°C), meaning their mowing season ends abruptly. Understanding the turf type allows the lawn owner to accurately judge when the plant is signaling the cessation of active growth.
Preparing the Lawn for Winter Dormancy
Once the decision is made to stop mowing, a few final steps maximize the lawn’s chances of successful winter survival. The most important final action is to perform a slightly shorter last cut before the deep cold sets in. Cool-season grasses should generally be cut down to a height of 2 to 2.5 inches. This height helps prevent the blades from matting down under snow, which reduces the risk of fungal diseases like snow mold.
Another element is applying a specialized winterizing fertilizer, characterized by a high concentration of potassium (K). Potassium strengthens the plant’s cell walls, improving its tolerance to cold temperatures and resistance to disease. This late-season feeding encourages root growth and carbohydrate storage, providing the energy reserves the grass will rely on until spring growth resumes.