Cool Season grasses are used extensively though-out the Northern areas of the USA. As with all cool season grasses their best growth periods are in the Spring and Fall. Summer time and winter brings on dormancy in these grasses. Many of the cool season lawns planted in the North today are cultivars of improved varieties of the three major cool season grasses -- i.e.: Bluegrasses, Fescues & Perennial Ryegrass. These improved variety mixes work together in special ratios of each grass to provide a better lawn in the various different conditions that exist across many lawns.
Warm Season grasses are planted throughout the South from an area west of Texas to as far north as Tennessee and North Carolina.
Transition grasses are nothing more than either Warm Season or Cool Season grasses. Sometimes they are specific mixtures of different types of grasses. Within the transition zone, no one type of grass will do well in all weather conditions (heat / cold). This makes for a difficult situation where either more intensive maintenance of a cool season grass is required, or the use of a summer time warm season grass which goes dormant (and brown in color) in the cool days of fall & winter. During the summer months, the cool season grasses decline due to the hot weather in Transition zones. Planting one of the more "cold hardy" warm season grasses can help keep your lawn in shape and green through the summer. Cool season grasses must be inter-seeded in these lawns to maintain a green appearance during spring and fall/winter seasons. The best way to determine a good "warm season" grass to plant in your lawn for summer purposes is to see what your neighbors have good luck with. Areas can vary so much within the transition zone due to temperature differences and soils that using "suggested" grasses for your specific area can be misleading. What works best is usually what others plant successfully. Which is best????? Zoysia, Bermuda and Buffalograss are three of the more commonly planted warm season grasses used in the cooler transition zone areas. Fescues, Ryegrasses and Bluegrasses are also very popular and used quite extensively in the transition zone. While there is no one rule of thumb about which grass works best, cool season grasses seem to be the more popular choices for the majority of lawns planted in the transition zone.