Warm Season vs. Cool Season Grasses

What is the difference between warm season grasses and cool season grasses? And here in North Texas, how much does it matter?

In the Dallas/Fort Worth area, most turf grasses are going to be of the warm season variety. They simply work best in this area’s agricultural growth zone, which is zone 7.

Zone 7 essentially means our winters are mild and our summers are hotter than further north. It also means we get a moderate amount of rainfall. So when it comes to grass types that will work well in our region, these conditions are best suited for warm season grasses.

But what if you want to mix a few grass types so that you can have a mostly green turf all throughout the year?

That is likely the most common reason people in this area look into the similarities and differences between warm and cool season grasses. Let’s start by taking a look at some similarities.

Common Traits

The very top of our state, to include the Panhandle and the north Texas/Oklahoma border, is considered a Transition Zone. That means it encompasses the overlap in altitude, temperature ranges, and precipitation where both cool and warm season grasses thrive.

However, that does not mean that the Transition Zone is the only place where both grass types can do well. In fact, there is a potential for cool season grasses to grow well in agricultural zones 4 through 10, and for warm season grasses in agricultural zones 3-11.

Cool season grasses go into active growth at 40 to 45 degrees F, and they reach optimal growth at 60 to 75 degrees F. Warm season grasses go into active growth at 60 to 65 degrees F, and they reach optimal growth at 80 to 95 degrees F.

In short, agricultural zones 4 through 10 can potentially support both cool and warm season grasses, so long as the seasonal temperature range remains between 40 and 90 degrees F, with adequate precipitation.

Main Differences

The biggest difference between cool season and warm season grasses isn’t necessarily where they grow best, but why that actually is. The thing is, there are some basic biological differences between the two grass types that make them more or less fit for different regions.

Warm Season Grasses

Warm season grasses photosynthesize a bit differently than cool season grasses. For one thing, they produce less protein. However, they also produce less non-protein nitrogen during photosynthesis, which makes the protein more available as an energy source.

For another thing, warm season grasses are better equipped to remain hydrated even during periods of photorespiration. This is a similar process to an animal sweating in higher temperatures. Warm season grasses require less water during photosynthesis, and are less likely to dry up in the heat of summer.

Visit our Irrigation Maintenance service page to learn how JC’s Landscaping can help you install and maintain a lawn irrigation system that best serves your personal lawn and landscape features.

Cool Season Grasses

Cool season grasses tend to go dormant during periods of drought and high heat. They may look dead, but much like in winter for warm season grasses, the grass is simply “asleep” in order to protect itself from extreme photorespiration. Once adequate moisture becomes available, the grass will “green up” again.

While it is possible to keep cool season grasses looking green throughout the winter, this can become expensive. That is because they require significantly more water for the process of photosynthesis. Add to that the fact that there are fewer daylight hours even in regions with mild winters, and there is simply more work that goes into keeping it green.

Can I Mix?

If you’d like to have a yard that remains green year-round, then choosing a warm/cold blend is an option. Here in North Texas, we are in agricultural zone 7, which is partially conducive to many cool season grasses you can add in with your warm season grass bed.

For those who choose to plant a mix, it is important to research the ideal fertilization schedules for the particular grass types you’ve selected. Lining up the schedule for both warm and cool season grasses may not be an exact science. But if you know what each grass breed needs in order to thrive, you can approximate the timing of your application to accommodate as accurately as possible.

Learn more about JC’s Best Grass Fertilizing Tips.

Keep in mind that cool season grasses need more water in order to adequately absorb supplemental nitrogen found in fertilizer mixes. Again, propagating a cool season grass in a warmer climate may require additional costs and resources, which is a significant consideration when budgeting your utility costs and lawn care needs.

For those with a heavily shaded lawn, one option is using a “sun and shade” blend that includes cool season grasses that are more shade tolerant than their counterparts. These blends can be found online and at many home and garden warehouses.

 

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