Kentucky Bluegrass (KBG) does not typically remain green throughout the winter months. While it is a cold-hardy turf variety, it responds to sustained low temperatures by entering a state of winter dormancy. This natural process causes the grass blades to lose their color and turn straw-brown until favorable growing conditions return in spring. KBG is a perennial grass popular for its dense, dark-green color and ability to self-repair during its active growing season.
Kentucky Bluegrass as a Cool Season Grass
Kentucky Bluegrass is classified as a cool-season turfgrass, which dictates its preference for specific temperature ranges. The grass thrives and exhibits its most vigorous growth during the cooler periods of spring and fall, with optimal growth occurring when daytime air temperatures are consistently between 60°F and 75°F. When temperatures fall below this range, the grass slows its metabolic activity to conserve energy. As soil temperatures drop below approximately 50°F, the grass significantly reduces its growth rate, which dictates its visual change during the winter, unlike warm-season grasses that enter dormancy during summer heat.
When and Why Bluegrass Turns Brown
The browning of Kentucky Bluegrass is a result of entering winter dormancy, a protective survival mechanism, not a sign of death. This state is triggered by prolonged periods when air temperatures consistently fall below 55°F to 60°F. The grass pulls nutrients and chlorophyll from its leaf blades down toward the crown and root system for storage.
The loss of chlorophyll, the pigment responsible for the green color, causes the turf to turn brown or tan. The grass halts above-ground growth, focusing energy on protecting the crown and rhizomes, which remain alive underground. Browning can also be hastened by winter desiccation (lack of available moisture).
It is important to distinguish this dormancy from “winter kill,” which is the actual death of the plant caused by factors like prolonged ice cover or severe dehydration. A dormant lawn will eventually green up, whereas winter-killed patches will not recover.
Winter Care for Dormant Bluegrass
Proper winter management focuses on protecting the dormant plant crown and ensuring preparation for spring green-up. A late-season fertilizer, often called a dormant feeding, should be applied late in the fall just before the ground freezes. This allows the grass to store nutrients in its roots for use in early spring, promoting a faster color return.
Homeowners should minimize foot or vehicle traffic on the lawn, especially when the grass is frozen solid or dormant. Pressure can damage brittle blades and exposed crowns, leading to patchy spots in the spring. Occasional light watering (about a quarter-inch) is recommended during prolonged winter drought when the ground is not frozen to prevent the crowns from drying out completely. Mowing the lawn slightly shorter in the final cut of the season helps prevent matting under snow, reducing the risk of snow mold development.