Warm vs. Cool Season Grass

March 13, 2013

US Turf ZonesYou may have noticed that grasses are either labeled as "cool season", or "warm season". This can be quite confusing for the average person not in the turf industry, and understandably so. You may hear the seasonal terms and think that these grasses are incapable of surviving outside of their respective season; that warm season grasses thrive in summer and cool season grasses thrive in winter. However, this is not quite the case. It’s a little more complex than that. Lets take a look at these categories of grass to take the confusion out of the equation and explain exactly what the differences between the two grasses are (and what you call the place in between).

The Differences

Warm season grasses do thrive during the "warm season" of Spring and Summer when temperatures are between 80° and 95° F. Cool season grasses grow best in temperatures between 65° and 75° F and will struggle when temperatures get into the 80s and 90s. That being said, cool and warm season grasses have nothing to do with the time of year the grass thrives, for both categories the growing season is the spring and summer to early fall. Instead, it refers to the regional locations where temperatures are in the optimal ranges for the majority of the year. So, cool season grasses would be best suited for the annual climate in northern regions while warm weather grasses are better for living in southern regions in the U.S.

Cool Season Grass

For the most part, cool season grasses grow well in the Northeast and much of the Midwest and Pacific Northwest. These areas are typically cool and humid, which are perfect conditions for cool season grasses to thrive. Some warm season grasses are also found in the western and southern parts of this region during short periods of warmth. Cool season varieties include bluegrass, tall fescue, fine fescue, and rye grass. The cool arid zone of the Midwest and Western states also permit cool season grasses to thrive as long as irrigation is available. Certain varieties such as wheatgrass and Canada bluegrass are also well adapted for the cooler parts of the region due to their ability to endure dryer conditions. Cool season grasses do not go dormant, but some do suffer from "rust" or get covered in snow during the late fall and winter months.

Warm Season Grass

Warm season grasses are more often found in the warm arid and warm humid states of the south and southwest. The humid areas surrounding the Gulf are best suited for Zoysia, St. Augustine, bahiagrass and centipedegrass while the arid parts of the region typically are best for Bermudagrass because of its excellent drought tolerance. During the cooler winter months, many cool season grasses are used for overseeding to provide a green lawn all year long. This is due to the fact that warm season grasses become dormant and turn brown once soil temperatures drop to below aproximately 65 degress Fareinheight. For homeowners looking to have a beautiful green lawn throughout the year, overseeding with a cool season variety such as annual rye can make that happen in traditional warm season regions.

The Transition Zone

There is also an area of the central and eastern United States called the transition zone from parts of North Carolina to Northern Virgina that cuts across the country. This is the most difficult area to grow grass because it gets too cold for warm season grasses during the winter and too hot for cool season grasses during the summer. Because of this, many turf professionals use a mixture of grasses in the transition zone to accommodate different times of the year (Overseeding). Historically, the Transition Zone areas have used cool season grasses such as Tall Fescue, but we are seeing a warm season push further north with some of our new varieties such as Latitude 36 Bermuda out of Oklahoma State and Geo Zoysia because of their excellent cold tolerance. 

No matter what region of the U.S. you live in, Sod Solutions can provide you with the right grass for your area. Simply use our Turf Grass Selector to narrow down your search for the best grass for your needs. Our network of more than 600 growers and distributors are there to help you with your decision and can be found using our Where to Buy tool.