Bermuda grass (Cynodon dactylon) is a perennial warm-season turfgrass known for its aggressive growth and heat tolerance. Originating in tropical and subtropical regions, its performance is intrinsically tied to temperature. As a warm-season variety, it thrives in conditions that cause cool-season grasses to suffer from heat stress, but this adaptation defines its strict temperature requirements. Understanding these thresholds is crucial for successful cultivation.
The Starting Point: Temperatures for Growth Initiation
Bermuda grass remains dormant throughout the colder months, conserving energy. To break dormancy and initiate spring green-up, the grass requires sustained soil warming, not just warm air days. The resumption of growth requires a consistent soil temperature, measured at a depth of a few inches, that rises above \(60^\circ\text{F}\) to \(65^\circ\text{F}\).
This threshold signals to the underground rhizomes and stolons that conditions are stable enough for active cell division and shoot elongation. Root growth slows significantly below \(50^\circ\text{F}\), restricting the plant’s ability to take up nutrients before dormancy sets in. When planting new seed or sod, an ideal soil temperature between \(65^\circ\text{F}\) and \(70^\circ\text{F}\) is necessary for quick germination and strong initial root development.
Peak Performance: Optimal Temperature Range
Once growth is initiated, Bermuda grass enters its most productive phase when air temperatures are consistently high. The optimal air temperature for maximum shoot growth is between \(80^\circ\text{F}\) and \(95^\circ\text{F}\), with some varieties performing best up to \(100^\circ\text{F}\). This high-temperature preference is explained by its unique physiological process known as C4 photosynthesis.
C4 plants efficiently fix carbon dioxide in hot, bright conditions, allowing them to continue rapid growth when cooler C3 grasses struggle. This provides a competitive advantage in intense heat and sunlight, translating to superior water and nutrient use efficiency during the summer. In this optimal range, the grass requires significant water and nutrient resources to sustain its growth rate and recover quickly from wear. Maximum root growth also occurs at elevated soil temperatures, typically between \(75^\circ\text{F}\) and \(85^\circ\text{F}\), which helps the plant withstand summer drought conditions.
Preparing for Winter: Dormancy and Cold Damage
As seasons change, the grass prepares for its annual dormancy period in response to decreasing day length and falling temperatures. Growth slows noticeably below \(60^\circ\text{F}\), and the plant enters full winter dormancy when temperatures consistently fall below \(50^\circ\text{F}\). This response stops chlorophyll production, causing the blades to turn brown, while conserving energy in the protected underground crown, rhizomes, and stolons.
The distinction between dormancy and lethal cold damage is significant. While a light frost only affects the leaf tissue, the grass can be killed entirely if the soil temperature drops too low for too long. Low-temperature kill is possible when the temperature around the crown falls to \(25^\circ\text{F}\) or below for an extended duration. Direct kill of the plant crown can occur near \(10^\circ\text{F}\), although this lethal threshold is influenced by the specific cultivar, soil moisture, and protective snow cover.