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 go dormant in the winter. Cool season grasses, however, flourish during the cooler periods of the year and go dormant in the summer. This article mainly focuses on winter dormancy for warm season grasses and what homeowners need to know about maintaining their lawns during this period.

homeownAs the name suggests, warm seasons grasses thrive in the heat of summer. During the warm summer months, warm season grasses like zoysia grass, centipede grass, St. Augustine grass or bermuda grass 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. They lose their green color and transfer their metabolic energy to their 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’s important to meet these needs during the winter because it becomes hard to tell if the grass is dormant or damaged until it greens back up 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 homeowners should stop watering their lawns altogether—a dormant lawn is still alive. Assuming various regions receive periodic winter rainfall, it should be acceptable to turn off irrigation systems during the winter months. No amount of watering will “green up” a dormant lawn that’s 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.

Do I need to mow a dormant lawn?

In short, the answer to this question is no, homeowners will not need to mow their lawns while they’re dormant. After Halloween, the lawn’s growth will begin slowing down, and by Christmas it will have stopped growing altogether. Mow the lawn for the last time of the season somewhere between those two dates. Mowing the lawn will not be necessary again until sometime between St. Patrick’s Day and Easter. For now, substitute the time spent mowing during the active growing season and winterize the lawn mower so that it’s in great shape for 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’s some variability between different species and cultivars, but generally speaking, all warm season grasses will have broken out of dormancy and turn green as early as March but no later than May. Exact times can also vary depending on each homeowner’s 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. Therefore, it’s important to provide warm season lawns with the appropriate nutrients before they go 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 the grass has the nutrients it needs to survive during dormancy since it will no longer absorb any nutrients applied during its dormancy period.

In the late fall, provide the lawn with phosphorus and potassium as well as other essential micronutrients.

This article was written by Sod Solutions Content Strategist, Valerie Smith.