Grass dormancy is a natural, protective state that allows the plant to survive adverse environmental conditions. This biological response is a mechanism for conservation, significantly slowing the grass’s metabolic processes. By halting growth, the plant redirects limited resources to safeguard its most vulnerable parts, primarily the crown and root system. This temporary pause ensures the grass can recover and resume normal growth once favorable conditions return.
The Two Categories of Lawn Grasses
Turfgrasses are broadly categorized based on their optimal growing temperatures. Cool-season grasses, such as Kentucky Bluegrass, Fescues, and Perennial Ryegrass, thrive when temperatures are between 60 and 75 degrees Fahrenheit. Their most vigorous growth occurs during the cooler periods of spring and fall.
Conversely, warm-season grasses are adapted to flourish in heat, generally preferring temperatures between 80 and 95 degrees Fahrenheit. Common examples include Bermuda grass, Zoysia grass, St. Augustine grass, and Bahia grass. These varieties exhibit their strongest growth throughout the summer months when heat is most intense.
Timing and Triggers for Dormancy
For cool-season varieties, the most common trigger for dormancy is prolonged high temperatures and insufficient moisture. When air temperatures consistently exceed 85 degrees Fahrenheit and the soil dries out, the grass enters summer dormancy, often in mid-to-late summer. This state protects the plant from desiccation and heat stress, conserving the water supply.
A secondary, deeper dormancy occurs for these grasses in the winter when air and soil temperatures drop significantly. True physiological dormancy is induced by extremely cold conditions, shielding the grass crown from freezing damage.
Warm-season grasses enter dormancy when the environment becomes too cold for their metabolic processes. The primary trigger is dropping soil temperature, typically falling below 50 to 55 degrees Fahrenheit. This usually occurs in late fall or early winter. As the soil cools, the grass stops producing chlorophyll and slows its metabolism to survive freezing temperatures. Warm-season grasses are tolerant of summer drought and heat, rarely entering heat-induced dormancy unless conditions are severe and prolonged.
Appearance and Care During Dormancy
The visual indication that turfgrass has entered dormancy is a widespread change in color from green to a straw-like brown or tan hue. This browning is often mistaken for death, but it signifies the above-ground blades drying out and sacrificing themselves. The texture of the grass changes dramatically, becoming stiff and brittle to the touch.
Homeowners should adjust maintenance routines immediately upon observing dormancy. Mowing should be significantly reduced or ceased entirely, as growth has stopped and traffic can damage the dormant crowns. Fertilization is prohibited because applying nitrogen can stimulate growth that the stressed root system cannot support, leading to potential permanent damage.
If the grass is experiencing summer, drought-induced dormancy, a small amount of water is necessary for survival. Applying about a quarter-inch of water every two to three weeks is sufficient to keep the plant’s crown hydrated without encouraging growth. This differs from deep winter dormancy, where the plant is fully insulated and watering is unnecessary due to freezing.