Bermuda grass is not a cool-season grass; it is classified as a warm-season turfgrass. This classification dictates when the grass grows most actively and how it reacts to colder temperatures. The distinction between warm and cool-season grasses is based on the specific temperature range in which the plant’s biological processes operate most efficiently. This difference affects the grass’s appearance, maintenance needs, and regional suitability.
Understanding Grass Classifications
The fundamental difference between grass types lies in their photosynthetic process, which is how they convert light into energy. Cool-season grasses (C3 plants) utilize a pathway most productive in moderate temperatures. Their optimal growth occurs between 60°F and 75°F, starting when soil temperatures reach 40°F to 45°F.
Warm-season grasses (C4 plants) have a photosynthetic process that is more efficient at higher temperatures and requires less water. These grasses thrive in heat, with an optimal growth range between 86°F and 95°F. Growth does not begin until soil temperatures are consistently 60°F to 65°F, allowing C4 grasses to flourish in summer heat.
The Specific Behavior of Bermuda Grass
Bermuda grass is a warm-season grass known for aggressive growth and superior tolerance for heat and drought. It has one of the fastest growth rates among warm-season types, spreading quickly via above-ground stolons and below-ground rhizomes. This enables the grass to withstand heavy use and recover rapidly from damage, making it a popular choice for sports fields and golf courses in the southern United States.
The grass’s major limitation is its reaction to cold, which causes it to enter winter dormancy. This occurs when soil temperatures consistently drop below 50°F to 55°F. As the plant conserves energy and ceases growth, the chlorophyll breaks down, causing the turf to turn brown.
In the spring, active growth resumes only when nighttime air temperatures consistently reach 60°F and soil temperatures exceed 65°F. This extended dormancy limits Bermuda grass primarily to the southern half of the country. While it survives in the “transition zone” where both warm and cool seasons occur, prolonged cold makes it susceptible to winter injury, which can require extensive repair.
Common Alternatives for Cooler Zones
For regions with significant cool periods, C3 grasses offer the necessary cold tolerance and active growth during spring and fall.
Kentucky Bluegrass
Kentucky Bluegrass is a preferred cool-season choice that forms a dense, attractive turf. It spreads by underground rhizomes, allowing it to self-repair and fill in bare patches. It requires consistent maintenance and full sun to thrive.
Tall Fescue
Tall Fescue is valued for its deep root system, which provides excellent drought and heat tolerance compared to other cool-season varieties. It performs well in both sunny and partially shaded environments. Tall fescue is a bunch-type grass, meaning it spreads through tillers, but it requires overseeding to correct damage.
Perennial Ryegrass
Perennial Ryegrass is often included in seed mixes because it germinates quickly, helping to establish the lawn rapidly. It provides a rich, dark green color and has high wear tolerance. Unlike Kentucky Bluegrass, it does not spread by rhizomes. It is generally used to provide quick cover or to overseed dormant warm-season lawns for winter color.