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Why Is My Zoysia Lawn Turning Brown? 4 Key Causes Explained


4 reasons zoysia lawn turns brown

Zoysia is supposed to be a plant-it-and-forget it turf grass, so it can be frustrating when your supposedly “maintenance-free” lawn turns brown. Luckily, there are only a few reasons zoysia turns brown, and the turf can make a full recovery with the right management or treatment.

So, why does zoysia turn brown? There are four common reasons your zoysia lawn may turn brown:

  • Dormancy
  • Chinch bugs
  • Brown patch
  • Winter kill

These conditions are easy to identify and treat, and with proper management, your lawn should make a full recovery.

Let’s look at each of causes and what you need to do to get your zoysia lawn thriving again.

Brown Zoysia Lawn: Dormancy

There are two reasons a zoysia lawn will go dormant: consistent temperatures under 55 degrees, or more than 6 days of dry weather.

Dormancy is not dangerous. Grasses are programmed to go dormant during extreme weather conditions. The ability to halt active growth is what allows them to survive extremely hot, cold, or dry climates.

Cold-Weather Dormancy

Zoysia is a warm-season grass that goes dormant as soon as cooler temperatures set in. If your entire lawn turns brown in mid fall, this is most likely due to a normal response to quit active growth during the winter.

You may notice some parts of your lawn going dormant before others.

  • The lawn on the north side of your house may go dormant before the lawn on the south side of your house.
  • Or, grass under trees may go dormant before grass in full sun.

However, the entire lawn should go dormant within a few weeks of low temperatures. If you notice prolonged brown patches in an otherwise green lawn, there may be an underlying problem.

Dry-Weather Dormancy

Zoysia is incredibly heat and drought resistant. It has a strong, deep root system that helps it to conserve moisture and nutrients during the stresses of summer.

Zoysia goes dormant after a week of hot, dry weather. Some homeowners confuse drought tolerance with the ability to stay green without moisture.

This is not the case.

Zoysia survives drought by quickly shutting down active growth and conserving resources. As soon as the lawn receives moisture, the grass will return to a lush, green carpet.

If your lawn turns brown in the heat of summer, irrigate .5”-1” in the early morning. If it does not return to its green color after a few days, you may have an underlying problem.

Chinch Bugs

Chinch bugs are the most common pests in a zoysia lawn. They are also the most commonly missed pests because they coincide with drought conditions and can be mistaken for dormancy.

The easiest way to distinguish drought dormancy from chinch bug damage is to observe the pattern of brown areas in your lawn.

How Chinch Bugs Damage Zoysia Grass

Chinch bugs will invade one side of your lawn and gradually creep deeper into your yard. If you pull up a tuft of grass, you will see small, black and red bugs living in the root system. The roots will pull up easily due to damage.

On the other hand, drought will affect the driest part of your lawn first and quickly spread to the other areas. The roots will still be strong and white if you pull them up, and the grass should green up after you irrigate.

How To Get Rid Of Chinch Bugs

Chinch bugs are almost impossible to control without chemical intervention. Spray at the first sign of invasion with an insecticide that targets chinch bugs (link to Amazon). You will have to spray every two weeks until the bugs are gone to keep new populations under control.

Chinch bugs are usually kept in check by beneficial insects, so there is no need to spray preventative insecticides. However, during drought conditions, beneficial insects either die off or go into hiding, giving chinch bugs free roam on your lawn.

You can prevent chinch bug infestations by irrigating regularly and continuing to improve the soil each spring through aeration and topdressing. This will give zoysia a strong foundation that helps roots fight off pest damage.

If your lawn is dying in brown patches during a drought, but you do not find chinch bugs, you may have an infestation of hunting billbugs or grubs. Treat accordingly.

Brown Patch

Brown patch is the most common disease that plagues zoysia. Brown patch is a fungal disease that occurs during hot, humid growing conditions.

Brown patch is identified by a brown ring encircling a green patch of grass. The infection starts small, but it can quickly take over the entire lawn. It can spread through water droplets, which is why it’s more common in humid climates or in lawns that are irrigated in the evening.

Zoysia does not like humidity. One of the easiest ways to prevent brown patch is by watering in the morning after the dew has dried. This can help eliminate the ability of the fungus to spread.

Over-fertilization can encourage brown patch, so try to avoid fertilizing zoysia lawns during the rainy season. Consider a natural lawn fertilizer if you are dealing with difficult soil such as clay.

Zoysia can tolerate poor fertility, so you may be able to avoid fertilization completely if you aerate and topdress each spring. This would improve the health of the lawn and the soil’s ability to drain, which also helps to prevent brown patch.

If you are unable to eliminate brown patch through a change in your irrigation schedule, you may need to apply a fungicide.

Other, less common diseases that affect zoysia lawns are rust and brown leaf spot. Both are easy to prevent with good maintenance practices and healthy soil.

Winter Kill

Zoysia does not tolerate cold temperatures. If you have a zoysia lawn in the northern part of the transition zone, you may experience intermittent winter kill. Luckily, this is easy to identify, and your lawn should be able to recover with proper summer maintenance.

However, if you live in a climate with consistently cold winters, you may want to consider replacing your zoysia lawn with a more cold tolerant grass.

Cold damage kills the top layer of leafy growth, leaving it dry and brown when the lawn should be coming out of dormancy.

You will notice new green shoots coming up intermittently from brown patches of grass that never come out of dormancy.

Winter kill usually affects shaded or lower portions of the lawn worse than sunny or sloped areas of the lawn. Cold air and standing water can pool in low areas, compounding winter damage.

If you notice winter damage in your lawn, try mowing at a shorter height than you would normally (1”) to remove as much of the dead leaf layer as possible (source). This will encourage a spurt of new growth, and the lawn should recover after a few weeks or months, depending on the damage.

If your lawn has mild to moderate winter kill, core aerate and topdress, then fertilize to encourage new growth. This process will trigger roots and crowns to put out new runners to fill in bare patches of soil, and introduce nutrition and oxygen into the soil to support vigorous growth.

Extreme winter kill may require removal of dead grass and replanting bare patches with zoysia plugs or sprigs. Buy Zoysia plugs that are guaranteed to grow or replaced free (link to Zoysia Farms).

The best cure for winter kill is time. Zoysia is able to repair itself with enough time and proper maintenance. If winter kill is an annual problem, consider planting a different, more cold-hardy variety of grass.

Read our complete guide to establishing and maintaining a healthy Zoysia lawn.

Conclusion

Zoysia lawns are incredibly resilient, and most are able to repair themselves with adequate irrigation, nutrition, and time.

The best way to prevent dying, brown patches of grass in any lawn is to follow the proper maintenance schedule and to continue to build up a healthy topsoil layer through aeration and topdressing.

For more information on how to establish a healthy lawn, visit Thriving Yard’s articles on establishing a lawn in clay soil and how to improve soils in existing lawns.

Sydney Bosque

Sydney has over 15 years of experience in lawn maintenance, landscape design, and organic gardening. She has an A.A.S. in Landscape Design/Organic Produce Production from the Nebraska College of Technical Agriculture.

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