Bermuda grass (Cynodon dactylon) is a resilient warm-season turfgrass known for its fine texture and ability to thrive in hot climates. It is genetically programmed to respond to changing seasons by entering a protective state known as dormancy. This natural process involves a slowdown or halt of growth, allowing the grass to conserve energy and survive periods of environmental stress, primarily cold temperatures, until favorable growing conditions return. Understanding this cycle is the first step in maintaining a healthy lawn throughout the year.
The Temperature Trigger for Dormancy
Dormancy is initiated by a sustained drop in temperature, signaling that winter is approaching. The most important indicator for Bermuda grass is the soil temperature, specifically at a four-inch depth. Growth slows significantly when soil temperatures consistently fall below 60°F (15°C) due to reduced metabolic activity.
The grass enters full dormancy when the soil temperature consistently drops to or below 55°F (13°C). At this point, the plant has difficulty producing chlorophyll faster than it is degrading, which triggers the visible color change. This threshold is typically crossed in late fall, usually between October and November in the transition zone, marking the general timing for dormancy to begin.
Visual Signs and Characteristics of Dormancy
The most noticeable sign that Bermuda grass has become dormant is a complete shift in color. The vibrant green of the active growing season fades to a uniform, straw-like brown or tan hue. This color change results from the plant ceasing chlorophyll production, the green pigment responsible for photosynthesis.
The grass is not dead; the brown blades indicate that above-ground growth has shut down. The plant pulls its nutrients and energy reserves into the crowns, stolons, and rhizomes beneath the soil surface for protection. During this period, both vertical and lateral growth stop entirely, and the grass will feel dry and brittle.
Preparing the Lawn for the Dormant Season
Preparing the lawn in the weeks leading up to dormancy helps ensure the grass successfully navigates the cold period and greens up quickly in the spring. A final, lower mowing cut is recommended before the grass enters full dormancy, maintaining a height of one to one-and-a-half inches. This lower height helps prevent the blades from matting down over the winter and reduces the risk of fungal diseases.
The application of a specialized winterizing fertilizer is beneficial during the early fall, focusing on a formula high in potassium. Potassium strengthens the root system and improves the plant’s tolerance to cold weather. Nitrogen-heavy fertilizers should be avoided in late fall, as they promote tender new growth easily damaged by frost.
Watering should be significantly reduced once dormancy is established. Irrigation is only necessary during extended dry periods, about once every two to three weeks, to maintain slight soil moisture. Spring green-up occurs naturally when the sustained soil temperature rises back to approximately 65°F (18°C) or higher.