Mowing a lawn that is not actively growing is generally discouraged, though the grass’s dormant state determines the level of potential harm. Dormancy is a natural survival mechanism where the plant temporarily stops growth to protect its crown and root system from environmental stress. Understanding this protective state is key to preventing long-term damage to the lawn.
Understanding Grass Dormancy
Dormancy is a protective, temporary shutdown that turfgrasses enter when conditions become unfavorable for active growth, such as during drought, extreme heat, or cold. The visual sign is the uniform browning or tan color of the leaf blades, which may make the lawn appear dead. However, dormant grass is alive, conserving resources until moisture and temperature conditions improve.
It is important to differentiate between grass that is dormant and grass that is truly dead. Dormant grass has a firm, intact root system, and the entire lawn typically turns brown relatively evenly. If you pull on the blades, they will resist coming out of the soil because the roots are still anchored and healthy.
The timing of dormancy depends heavily on the grass species. Cool-season grasses, like Kentucky bluegrass and fescue, primarily enter dormancy during the heat and drought of summer. Conversely, warm-season grasses, such as Bermuda and St. Augustine, typically become dormant in the late fall or winter when soil temperatures drop below approximately 55°F.
Consequences of Mowing Non-Growing Grass
Mowing dormant grass creates stress for a plant already operating in resource-conservation mode. When the grass is not growing, its ability to heal from the mechanical injury of a mower blade is severely compromised. The primary damage occurs because mowing removes the leaf tissue, which stores energy reserves in the form of carbohydrates.
These stored carbohydrates are the fuel source the grass relies on to survive stress and initiate new growth when favorable conditions return. Removing this reserved energy forces the plant to tap into the limited reserves in its crown and roots, weakening the entire structure. This reduction in stored energy can significantly delay the lawn’s recovery and green-up process.
Furthermore, the freshly cut tips of dormant grass blades are left vulnerable to desiccation, or drying out, and are more susceptible to disease pathogens. Since the grass is not generating new cells, it cannot quickly form a protective layer over the cut, allowing moisture loss and creating an entry point for fungal diseases.
Excessive mowing or traffic on dormant turf can also damage the crown directly. This may lead to patchy areas that fail to green up when the rest of the lawn recovers.
Safe Techniques for Dormant Lawn Maintenance
The most reliable maintenance practice for a dormant lawn is to avoid mowing altogether, as the grass is not generating new vertical growth. If a trim is necessary—perhaps to remove debris or address stubborn winter weeds—the “less is more” rule must be strictly followed. Any trimming should be done with the mower set to its highest possible height to minimize leaf tissue removal.
When mowing is unavoidable, never remove more than one-third of the existing blade height in a single pass, even if the grass appears completely brown. This ensures that a minimum amount of photosynthesizing tissue is available to the plant, which is especially important for cool-season grasses that may still have some green near the crown. Using a sharp mower blade is also necessary to ensure a clean cut rather than a ragged tear, which reduces the immediate stress on the plant.
It is crucial to consider the ground conditions before attempting any maintenance. Avoid mowing when the ground is frozen, as the brittle, dormant blades are highly prone to snapping and shattering, causing significant mechanical damage.
Similarly, refrain from using the mower when the ground is saturated or muddy. The weight of the equipment and foot traffic can lead to soil compaction, restricting the air and water flow that the roots need for survival.