Cool Season or Warm Season Grasses

It’s getting to be the time of year when people start thinking about their landscapes, and turf grass is an important part of the landscape. Maybe you are in a new home and have yet to start landscaping, or maybe you want to re-do a tired, worn out lawn. Where do you start? The place to start is picking the right variety of grass. Today’s blog is the first of several that will discuss turf grass and how to grow the best possible lawn.

The first step is to choose the grass, but it can be a very confusing process to select a new grass when there are so many species to choose from: bentgrass, bermuda, blue grass, buffalo grass and bahia, to list a few. To help sort out the species, a good starting point is to know that all grasses fit into two basic categories. All turf grass species are either cool-season grasses or warm-season grasses. Cool season, or sometimes called cool climate, are grass species that perform better in the cooler times of the year and thrive in temperatures ranging from 65° to 75°F. Cool season grasses also are better adapted to the cooler or temperate regions of the United States. Warm season grasses, also called warm climate, can grow in tropical regions. Warm season grass species thrive in a temperature range of 80° to 95°F, and they are best adapted to the warmer climates of the southern United States. Those are broad definitions, so now you will want to know some characteristics about each category.

Cool season grass characteristics:

  • Perform best with consistent rainfall or irrigation
  • Most growth is in the spring and fall
  • The turf can be seeded or sod
  • Growth will occur when soil temperatures are 40° to 45°F for established turf; a soil temperature of 55°F is needed for seed germination
  • Respond well to fertilization in the spring and fall
  • During summer, growth is reduced and dormancy is induced by high temperatures and low rainfall
  • Limited winter dormancy, retain green color
  • Good winter tolerance
  • Adequate shade tolerance

Warm season grass characteristics:

  • Require less water
  • Turf can be seeded (not all species), sprigs, or sod
  • Most growth at temperatures of 90° to 95°F
  • Soil temperature needs to be 60° to 65°F for seed germination and growth of established turf
  • Respond well to fertilization during the summer
  • Dormancy is triggered by shortened day lengths and colder temperatures
  • Extended winter dormancy with brown color
  • Poor winter tolerance
  • Poor shade tolerance

Cool season turf grass species:

  • Blue Grass
  • Fescues
  • Ryegrass
  • Bentgrass

Warm season turf grass species:

  • Buffalo Grass
  • Zoysia Grass
  • Bermuda Grass
  • Carpet Grass
  • Centipede Grass
  • Bahia Grass
  • St. Augustine Grass
  • Seashore Paspalum

Once you have a general understanding of the differences between warm season and cool season grasses, the next consideration is what climatic zone you live in. The United States can be divided into five primary zones:turfUSAadapt

  • Cool/Humid: This zone includes Northeast, a few of the Midwest states, and much of the Pacific Northwest. Any of the cool season species can be grown.
  • Cool/Arid: This zone includes much of the dryer areas of the Midwest and West. Cool season grass species are best adapted to this area when irrigation is available; however, Buffalo grass is becoming widely used in the warmer areas, such as Kansas, Nebraska, and Colorado for non-irrigated sites. Zoysia grass is also grown in the western and southern parts of this zone
  • Warm/Arid: This zone includes the Southwest states. (Use warm season grass species, same as for warm/humid, see below).
  • Warm/Humid: This zone includes the Southeast and Gulf states. Warm season grasses are best adapted to this zone. Bermuda grass is the most common species used but can suffer winter damage in the most northern areas. Zoysia grass is widely used in the northern parts of this zone. For the Gulf Coast states, carpetgrass, bahia grass, St. Augustine and Seashore Paspalum are widely used.
  • Transition: This zone extends through the central part of the United States and includes parts of each of the other four zones. Because the transition zone has cold winters that can kill warm-season grasses and hot summers that can kill cool-season species, this zone is the most challenging in which to grow turf grass. Many turf experts recommend tall turf type fescue for the transition zone as it is the most drought tolerant of the cool season grasses, and it is tolerant of cold winters as well. Other experts recommend using the most cold tolerant warm season grasses such as Yukon Bermuda.

When planning a new yard or wanting to make-over an existing yard, choose the grass species that best fits your conditions. Know your climate zone and pick a cool season grass or warm season grass that is best adapted to your zone. Picking the right grass is really the most important step!

Question for the week: What zone do you live in and what type of grass are you growing?

By Kimberly Bell

+Kimberly Bell

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