Types of Grass & Evapotranspiration

Cool-season Grass

• The cool-season area of the U.S. runs from the Atlantic Coast, through the Ohio Valley, across the northern Midwest plains and into the middle of California's coast. Grass in this zone thrive in cooler temperatures. Ideal soil temperatures for cool-season grass are between 50 and 65 degrees Fahrenheit, while the air temperatures should stay between 60 to 75 degrees Fahrenheit. Some examples of grass species that grow in this zone include fescue, bluegrass and rye grass.

Warm-season Grass

• The warm-season area of the U.S. extends from the North-South Carolina border, across the southern plains and into southern California. Ideal soil temperatures for grass in this area range from 70 to 90 degrees Fahrenheit, and the air temperatures range from 80 to 95 degrees Fahrenheit. Species in this area handle the drought conditions very well, but do tend to brown in the winter during colder weather. Plant a fast growth cool-season grass like rye grass to maintain your lawn's appearance in the winter. Warm-season species include bermuda grass, zoysia grass, and St. Augustine grass.

Transitional Zone Grass

• The transitional zone runs from the Mid-Atlantic coast in Virginia, across the Kentucky, and the middle of the plains states. It stops in the northern areas of southern California. The transitional zone is an area that gets hot enough in the summer to support a warm-season grass and cool enough to support a cool-season grass. Common grass seeds in the transitional zone include buffalo grass, zoysia grass, and fescue. It is more common to find a drought-tolerant cool-season grass in this area than a cold-hardy warm-season grass.

Evapotranspiration

• Evapotranspiration refers to the two methods that a plant can lose water. Evaporation is water that turns into a vapor and is transported up into the atmosphere. Evaporation occurs from water on the ground and in bodies of water. Transpiration is the process of water in plant tissue that turns into a vapor from the sun's radiant energy, and travels up into the atmosphere. The process of evapotranspiration is the combination of evaporation and transpiration. Evapotranspiration is important for gardeners because the rate of evapotranspiration affects the amount of watering needed for your lawn.

Watering Requirements

• Different species from the cool- and warm-season grasses have different evapotranspiration rates. From March to April fescue needs 1.5 to 2.0 inches of water, which will increase to 2.0 to 3.0 inches of water from June to August. Bluegrass has the same watering requirements for March through August as fescue. Buffalograss, which is a warm-season grass, only requires 1 inch of water from March through August.