St. Augustine Grass Turning Yellow: Reasons And Solutions That Work!

St Augustine is a warm-weather grass that has a faster growth and spread rate. Like any other type of grass, St. Augustine grass turning yellow is a common scenario. 

In most cases, if this yellowing is untreated, it results in the plants’ death, which means your beautiful lawn will be no more. Are you troubled with your St. Augustine grass.

Stick around to know the cause and its remedy.

Why Is My St. Augustine Grass Turning Yellow?

St. Augustine grass turning yellow

The yellowing of a plant indicates a lack or insufficiency of some nutrients. First, we will go deeper into the major causes of yellowing of this grass, and later on, we will look at the remedies.

  • Lack Of Nitrogen

Nitrogen is a component of the green coloring matter in plants, commonly known as chlorophyll. It enables the plant to absorb the sunlight energy which is needed for photosynthesis.  

Nitrogen is also present in the plant’s roots and ensures efficient uptake of water and other nutrients from the soil.

Consequently, if there is insufficient nitrogen for the grass, the processing of chlorophyll will be poor, resulting in the fading of the green color. Other plants like your orchid leaves will turn yellow too due to lack of it!

Additionally, its absences will result in poor water absorption and other nutrients from the soil resulting in the yellow color.

  • Root Rot

Ruinous root rot is a fungal disease that is also characterized by yellowing of the leaf blades. This disease is caused by excess nitrogenous fertilizer, which reduces the absorptions of oxygen in the growing substrate.

The lack of oxygen creates a favorable environment for the growth of several types of fungi, leading to the decomposition of the root and, later, the leaf blades’ yellowing.

  • Chinch Chaos

Chinch is a common pest in St. Augustine grass that leaves small patches of dead grass surrounded by a thin circumference of yellow grass.

  • Chemical Concerns

Chemicals have a low PH which results in their corrosive nature. For example, when spilled on a lawn, it destroys the leaf matter’s formation, which results in poor absorption and usage of the nutrients.

As a result, it gives the yellow color.

St. Augustine Grass Disease Identification

yellowing St. Augustine grass

Most plant diseases are characterized by the change of color to yellow, red, or brown.

To treat the disease, you must first be able to identify the type of the disease.

In this section, we will discuss on steps of identifying three of the common St. Augustine diseases. Let’s get into it.

  • Pythium Lawn Disease

This disease is common during hot and highly wet seasons. It is usually characterized by patches of withered plants and blackened blades.

Also, the roots rot while the leaves stick or coil together.

  • Rust Lawn Disease

Rust lawn disease is caused by too much moisture or insufficient nutrients in the leaves. Its main symptom is yellowing of the leaves and patches of rust-like color. 

Furthermore, it is pretty common in warm seasons and the beginning of summer.

  • Summer Patch Lawn Disease

Lastly, we have the summer patch disease common in summer and areas with hot climates. Its symptoms are dead patches of the grass which are surrounded by healthy-looking grass.

What Are The Remedies?

lawn with St. augustine

After you have identified the cause of the yellowing of the grass next, you should treat it before it spreads further and causes the death of the entire lawn.

How do you do that?

Keep reading to learn tips to prevent and treat some of the St. Augustine grass.

  • Maintain An Optimum pH

Different plants thrive well in soils with varying levels of alkalinity and acidity. However, when the PH is higher or lower than needed, it results in poor absorption of nutrients, which will cause the death of the plant.

The St. Augustine grass thrives best in slightly acidic or on soils with a neutral PH.

Consequently, you should regularly test the PH of the soil and ensure that it ranges between 6.0 to 7.0. If it is lower, you can use vinegar or another acid to neutralize, and on the other hand, you can use baking soda if the PH is too high.

  • Fertilize Properly

We are always advised to fertilize our plants, and no one reminds us of the dangers of doing it the wrong way. Basically, under-fertilizing or over-fertilizing the lawn is bad and dangerous.

Let me explain that deeper! Under fertilizing will give the plant insufficient nutrients, resulting in poor absorption and a slower growth curve, and later the death of the plant.

On the other hand, over-fertilizing will decrease oxygen in the plant substrate, resulting in poor germination, photosynthesis, and many other plant processes.

Consequently, you should apply only the correct amounts of fertilizer as advised by the manufacturer.

  • Water The Lawn

Watering the lawn is more than just setting the sprinkler and leaving the whole day. It would be best if you were careful about how regularly and when you water it.

Ideally, you should water the lawn early in the morning before the sun sets in and increase the evaporation rate before the plants absorb the water.

Another rule is that you shouldn’t water frequently but deeply.  What do we mean?

Even though you want your lawn watered, it will be best to nature solid and deep roots which can withstand droughts.

Hence, watering it twice a week will provide the needed moisture and encourage deeper and spread out roots.

  • Use Pesticides

Pests are common in lawns. Unfortunately, they mostly go unnoticed and can only be identified after investing in a big part of the lawn.

Thus, you should always look out for any abnormalities in the yard, such as a change in color or patches of dead grass, and don’t hesitate to get a pesticide.

The Best Fungicide You Can Try

Fungi cause decomposition of the roots, which leads to yellowing of the leaves and ultimate death of the plant. Unfortunately, getting the best fungicide is not always an easy drive.

For that reason, we will recommend some of the fungicides tested and confidently apply them on the St. Augustine grass.

But before that, you should go through the St. Augustine grass disease identification process to confirm that the cause of the disease is fungi.

  • Patch pro 

This fungicide is recommended for leaf spot disease. In addition, it contains propiconazole which is an active ingredient for restoring the color of the plant.

  • Azoxystrobin

This is an organically made fungicide with a broad spectrum of active ingredients to instantly destroy multiple types of fungi.

  • Fluoxastrobin

Fluoxastrobin works by interfering with the respiration of the fungi and inhibit further multiplication. Therefore, it is highly recommended for St. Augustine grass for it prevents other effects and kills only the fungi without affecting the growth of the roots.

Other fungicides include

  • Propiconazole
  • Thiophanate methyl
  • Triadimefon

Frequently Asked Questions (FAQs)

What does Overwatered St Augustine grass look like?

The color will look more blue or grayish color instead of deep green color.

Why does St Augustine grass turn yellow in the summer?

During the summer, the root rot causes its grass to turn yellow.

How do you fix yellowing St Augustine?

For a quick fix, you can apply any nitrogen-iron combo like ‘Iron Plus’. But the best way is to apply any slow-release fertilizer and watering the lawn after the application.

What time of day is best to water St Augustine grass?

Early moring is the best time but try to do it before 10 A.M.

Can you use Epsom salt on St Augustine grass?

Yes, you can. It’s perfectly safe.


Watching your St. Augustine grass turning yellow can be very depressing, not to mention the destruction of the beautiful lawn and, worse, the waste of the expensive investment.

Nonetheless, to be candid is not always easy to treat grass yellowing. Why?

There are several causes of grass yellowing, and they all require different treatments. Well, don’t freak out! We have already discussed all that in this piece to help you restore your beautiful lawn in a few days.

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1 thought on “St. Augustine Grass Turning Yellow: Reasons And Solutions That Work!”

  1. I just put down seville st. augustine. It’s been down 2 months and was beautiful green. I added a fertilizer and next day yellowing has occurred. My response was to water more but I don’t think I should have now that I did it. Hoping I didn’t kill my new lawn.

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