Why Do Warm Season Lawns Turn Brown?

Most homeowners located within the southern two-thirds of the United States may notice periods of time when their grass turns brown from dormancy. This can happen for a variety of reasons such as a change in temperatures or from drought dormancy. Warm season grasses and cool season grasses go dormant at different times of the year due to the change in temperatures. Warm season grasses flourish during the warmer times of the year and will go dormant in the winter. Cool season grasses, however, flourish during the cooler periods of the year go dormant in the summer. Take a look at our blog on the differences between warm and cool season turfgrass varieties for more information. This blog mainly focuses on winter dormancy for warm season grasses and what homeowners need to know about maintaining their lawns during this period.

As the name suggests, warm seasons grasses thrive in the heat of summer. During the warm summer months, warm season grasses like zoysias, centipedegrass, St. Augustines or bermudagrasses are at their peak—they display great color, grow aggressively and make efficient use of water. However, when temperatures drop and remain below 65 degrees (typically sometime after mid-September), warm season grasses begin to slow in growth and eventually cease growing altogether. Soil temperatures are usually around 55 degrees Fahrenheit. The grass loses its green color and transfers the metabolic energy to its roots.

Similar to how some mammals hibernate in the winter, warm season grasses appear to be inactive in the winter and may look dead, when in fact, they are very much alive and have different needs than in the summer months. It is important to meet these needs during the winter because it becomes hard to tell if your grass is dormant or damaged until it greens back up in the spring. Take a look at the images below to see the difference between dormant grass and grass that is thriving during the warmer months of the year.

Pictured above from left to right: EMPIRE® Zoysia during its dormancy period and EMPIRE flourishing in the spring.

Do I need to water my dormant lawn?

Because dormant lawns are not actively growing, they have greatly reduced irrigation needs. This does not mean you should stop watering your lawn altogether—a dormant lawn is still alive. Assuming your region receives periodic winter rainfall, you should be able to turn off your irrigation system during the winter months. No amount of watering will “green up” a dormant lawn that is brown. Moreover, excessive moisture in September and October can lead to damaging fungus outbreaks. The one instance when winter moisture is beneficial in a dormant lawn is just before an excessive cold event because the combination of freezing temperatures and a desiccated lawn can lead to winterkill. Take a look at some of the images below to see what a few different late fall disease outbreaks may look like. To learn more, read Beware of Late Fall Fungus in Warm Season Lawns.

Pictured above: Late fall fungus taking over a warm season home lawn indicated by the discolored circles above. This becomes harder to see until the lawn greens back up in the spring.

Do I need to mow a dormant lawn?

In short, the answer to this question is no, you will not need to mow your lawn while it is dormant.After Halloween, your lawn’s growth will begin slowing down, and by Christmas it will have stopped growing altogether. Somewhere between those two dates, you’ll mow your lawn for the last time of the season. You will not need to mow your lawn again until sometime between St. Patrick’s Day and Easter. For now, substitute the time spent mowing during the active growing season and winterize your lawn mower so that it is in great shape in time for the spring!

When do warm season lawns green up?

Warm season lawns break dormancy and begin to grow and regain their green color as air temperatures and soil temperatures increase. There is some variability between different species and cultivars, but generally speaking, all warm season grasses will have broken out of dormancy and turn green and grow as early as March but no later than May. Exact times can also vary depending on your geographic location.

Which winter fertilizer should I use on my dormant grass?

Dormant lawns cannot absorb any nutrients at this time, so applying fertilizer in the winter is ineffective. Just as a hibernating bear cannot eat a meal while hibernating, a dormant lawn cannot take up nutrients that are applied. This is why it is so important to provide your warm season lawn with the appropriate nutrients before it goes dormant. As previously stated, dormant grass transfers all of its metabolic energy to its roots, so the nutrients are stored in the grass roots instead of the blades. It’s important to make sure your grass has the nutrients it needs to survive during dormancy since it will no longer absorb any nutrients you apply during its dormancy period.

In the late fall, you want to provide your lawn phosphorus and potassium and other essential micronutrients. The Lawnifi® Fall Fertilizer Box will give your lawn everything it needs before going dormant in the winter so that it can store those nutrients and survive the cooler months ahead. However, when spring comes, it will be time to resume fertilizing your lawn. This is when you can use the Lawnifi Spring Fertilizer Box, an easy-to-use liquid fertilizer program powered by Catalyst Technology^TM. Catalyst Technology helps plants better absorb nutrients with the use of less product. The Spring Fertilizer Box is designed to help your lawn transition from the winter season to warmer weather in the spring.

For more information about winter dormancy, check out Winter Lawn Maintenance Tips and How to Keep Your Lawn Green During the Winter.