What Are Cool Season Grasses?

What Are Cool Season Grasses?

Cool-season grasses are grass types that thrive in areas with cold winters and hot summers.

Cool-season grasses have adapted to grow well in areas of the country that experience tremendous temperature fluctuations: cold, freezing winters and hot, dry summers. However, these grasses grow best when temperatures are between 60-75 degree F, which is why they grow most actively in the spring and fall. Cool-season grasses are most commonly grown from seed, although sod is also available, and they grow best when they are maintained at a mowing height of 3-4 inches.

Where Do Cool-Season Grasses Grow?

Cool-season grasses grow in the upper two-thirds of the United States. In the top-third (or the area roughly defined as New England, the Upper Midwest, High Plains, Northern California, and Pacific Northwest) typically only cool-season grasses are grown. The middle-third (also known as the “Transition Zone”) is the area of the country where cool-season and warm-season grasses overlap. Cool-season grasses grow well there because they are adapted to the cold winters. Tall fescue is especially well suited for the Transition Zone because of its high heat and drought tolerance. However, some warm-season grasses also grow well there because of the hot, dry summers. Bermudagrass and zoysiagrass are the main warm-season grasses found in the transition zone because they are drought-tolerant and also able to withstand cooler temperatures better than other types of warm-season grasses. However, they often go dormant and turn brown during the winter months when temperatures are consistently below 60 degree F.

Types of Cool-Season Grasses

The most common types of cool-season grasses are Kentucky bluegrass, perennial ryegrass, fine fescue, and tall fescue. You'll often find the seeds of these grass types mixed together for different needs and uses, such ashigh traffic,sunny, ordense shadeconditions. The most popular and most versatile cool-season grass mix is forsun and shade.

Kentucky Bluegrass

Kentucky bluegrass is a very popular cool-season grass in the northern U.S. It has an aggressive spreading habit and dark green leaves. Bluegrass holds up well in high traffic areas of the yard, areas with moderate shade, as well as sunny areas and under scorching heat. Because of its spreading habit, it will grow to fill in bare spots in the yard.

Drought Tolerance – Medium
Foot-Traffic Tolerance – Medium
Shade Tolerance – Low to Medium
Cold Tolerance – Medium
Heat Tolerance – Medium

Perennial Ryegrass

Perennial ryegrass is a bunch-type (a.k.a. "non-spreading") cool-season grass that germinates quickly after seeding. It is a fine-bladed grass that is ideal for high-traffic areas of the yard. Ryegrass is also used for erosion control because of its quick germination. It is usually recognized in a lawn by the whitish cast the top of the grass blades have after mowing. Perennial ryegrass along with annual ryegrass is also commonly used in the southern U.S. to dormant overseed certain warm-season grass lawns so homeowners can have a green lawn during the cool winter months.

Drought Tolerance – Low to Medium
Foot-Traffic Tolerance – High
Shade Tolerance – Low to Medium
Cold Tolerance – Medium
Heat Tolerance – Low to Medium

Fine Fescues

There are several types of fine fescue—creeping red fescue, chewings fescue, sheep fescue, and hard fescue. Fine fescues have a very fine leaf texture and a gray-green color. They are popular in grass seed mixes because of their fast growth rate as well as their shade tolerance.

Drought Tolerance – High
Foot-Traffic Tolerance – Medium
Shade Tolerance – High
Cold Tolerance – Medium to High
Heat Tolerance – Low to Medium

Tall Fescue

Tall Fescue is a bunch-type grass that produces a deep root system. It is very popular in the Transition Zone because of its heat and drought tolerance. There are tall fescue blends, like Southern Gold® Mix, that contain varieties bred in the south that are able to survive the extreme weather conditions. Turf-type varieties of tall fescue have a finer leaf texture and darker green color than the older tall fescue varieties, like Kentucky-31 tall fescue. Heat-Tolerant Blue® Mix is a tall fescue mix that contains Thermal Blue™ Kentucky bluegrass which, unlike other tall fescue lawns, helps the lawn spread to repair wear and tear.