Climate Zones of the U.S.

Climate zones are a description of general temperature and humidity conditions in specific areas as it relates to turfgrass. The United States has four different zones for grass adaptation. The expanse of North American landscapes range from low deserts to high mountains, semi-tropics to northern rain forests. The zones of the U.S. are divided along these temperature and humidity variations. The climate zones in the northern U.S. extend upward in Canada.

Almost all grasses will grow in any zone for at least part of the year. However, certain grass types are better suited for some climate zones than others. Depending on where you live in the U.S. or Canada, there will be various grass types to choose from. Unlike some ornamental plants, you can’t bring your grass indoors when conditions no longer favor it, so choosing a good grass for your area is important.

Location Of Climate Zones

The climatic zones in the U.S. consist of Cool/Humid, Warm/Humid, Cool/Arid, Warm/Arid, and an additional area known as the Transition Zone. The transition zone stretches across the central part of the country from the extreme eastern edge of New Mexico to the central East Coast. Its width in places can be a few hundred miles. The transition Zone is considered to be the hardest place in the U.S. to grow quality turf. The following chart shows the location of the different climate zones.

Preferred Grasses In Each Climate Zone

• The Cool/Humid zone in the Northwest can receive a great deal of moisture. That can be problematic for some grass types because of prolonged soil moisture. The fescues, bluegrass, ryegrass, are common lawn grasses in that area. The State of Oregon is known for its production of high quality turf type fescues. Although the mild temperatures of the northeast favor cool season grasses, zoysiagrass and buffalograss can be found in the drier parts in the zone.
• The larger Cool/Humid section is in the Mid-West extending throughout the Northeast. Cool season grasses dominate in this area. Warm season grasses are not favored as much in this area because the summers are too short and the winters are too long and cold.
• In the Warm/Arid zone, Buffalograss and bermudagrass are commonly used grass types. This section stretches through the Southwest as far as central Texas. However, many homeowners in Southern California seem to favor tall fescue lawns even though summers can be quite long and hot. Sprinkler systems are necessary because temperatures can rise above 110 degrees for many days at a time. It is a testament to tall fescue's ability to survive heat that would kill other cool season grasses.
• The Cool/Arid zone located in the west is best adapted for cool season grasses as long as it is irrigated. Buffalograss is increasingly being used in many areas because of its drought hardiness.
• The Warm/Humid climate zone in the south is best adapted for warm season grasses. Bermudagrass is the most common grass type followed closely by St. Augustinegrass. Along the coastal regions, St. Augustinegrass seems to be preferred because of turf quality and good shade tolerance. Carpetgrass and Centipedegrass are also used along the coastal regions. Cool season grasses are not used very often in this region except when overseeding bermudagrass in winter.
• The area known as the Transition Zone is so named because of the transition between cool season grasses and warm season grasses. There is no one grass type that best fits this area. Its winter temperatures can be too cold for some warm season grasses and too hot in the summer for some cool season grasses. The exception may be perennial ryegrass, which may be better adapted to this zone than any other. However, tall fescue is probably the most popular cool season grass with bermudagrass and zoysiagrass being the most popular warm season grasses. St. Augustine is not grown here because of poor cold tolerance.

  I observed in southern Missouri that the majority of lawns were cool season grasses. When I crossed over the border into Arkansas, there was a sharp increase in warm season grasses, especially bermudagrass. This is a tricky area and can be difficult for homeowners to manage lawn grasses. This site will cover what you need to know for the best quality grass.

In Conclusion...

In every climate zone, grass will respond to light and temperature changes. Each grass species will emerge from winter dormancy as soil temperatures rise in spring. Cool season grasses will thrive best in temperatures of 65 to 75 degrees. Growth will slow as temperatures rise. Warm season grasses are better adapted for temperatures between 80 and 95 degrees and will go dormant as soil temperatures approach 50 degrees.

There are some exceptions, one being perennial rye. It is a cool season grass, but has poor cold tolerance and can be injured in the harsh northern winters. It is best used for overseeding warm season grasses or as a lawn grass in the transition zone.

One more thing that can help in choosing the right grass, is by checking out your local university extension office. They can help you with any specific questions you may have for your area. You can also look at the National Turfgrass Evaluation Program. The program tests the different grass types in different locations around the country to see how well they perform. Many of the nation's universities that have agricultural and turfgrass programs are the sites for these tests. Click here to access the National Turfgrass Evaluation Program website.