Why Is My St Augustine Grass Turning Yellow And What Will I Do About It?

Your St. Augustine grass is turning yellow because it needs more nitrogen.

If you have St Augustine grass in your yard, you may have noticed that some of the blades are turning yellow. This can be a sign of a few different problems, including over watering or a lack of nutrients.

What causes St Augustine Grass to turn yellow?

There are several reasons why your St Augustine grass is turning yellow. If the cause is over watering, then the grass will turn pale green to yellow and will dry out quickly. If there is not enough water, then the grass will turn brown and die back at the base of the plant. It’s also possible for your St Augustine lawn to turn yellow if it doesn’t have enough nutrients from fertilizers or soil amendments.

How do I fix this problem?

If you notice your St Augustine grass turning yellow after watering it, try watering less often but more deeply instead of watering regularly every day or every other day with a sprinkler system. The deep watering method encourages roots to grow deeper into the ground where they can access more water and nutrients than shallow root systems can reach on their own. You can also add compost or fertilizer to your existing soil to increase nutrient content and help keep moisture levels consistent throughout summer months when temperatures rise above 90 degrees Fahrenheit (32 degrees Celsius) daily average.

Soil pH issues

If your St Augustine grass has turned yellow, it’s probably because your soil pH is too high. The pH of the soil should be 6 to 7. If the soil is too alkaline, it can make your grass turn yellow.

To fix this problem, you’ll need to add sulfur to the ground. It’s a simple process that only takes a few hours: First, spread some sulfur on the ground and let it sit for 24 hours. Then mix it into the soil with a shovel or hoe and water thoroughly. This will help lower the pH of your garden and keep your St Augustine grass healthy!

Nitrogen deficiency

Nitrogen is an essential element for the healthy growth of plants. In order for a plant to absorb nitrogen, it must first be converted into ammonium and then nitrate, which can be taken up by the plant roots and used in photosynthesis.

When plants are deficient in nitrogen, they will turn yellow and grow slowly. The leaves become pale green or yellowish-green with irregular dark green stripes or blotches on the upper leaf surface and dark green veins on the lower surface of leaves. The stems become weak and spindly and may collapse under their own weight. This can be caused by a number of factors, including poor drainage, low fertility levels and over-watering.

How do you know if your St Augustine grass is suffering from a nitrogen deficiency? Here’s what you should look for:

  • Your lawn has very little color or has lost its color completely
  • Your lawn has thinned out significantly over time
  • You notice that your lawn is not growing as well as it was before

Too Much Fertilizer

St Augustine grass has been known to turn yellow when over-fertilized with nitrogen rich blends such as ammonium sulfate. This happens because nitrogen stimulates new growth, which can make plants appear greener than they actually are when they’re young but also causes them to burn when exposed to sunlight and heat. It’s easy for homeowners to over-apply nitrogen in an attempt to get more green color out of their lawns in hot summer months but this practice only makes matters worse!

To prevent your St Augustine grass from turning yellow again next year, try using a balanced fertilizer with equal amounts of nitrogen and potassium instead of using ammonium sulfate or other high-nitrogen products.

Note: Nitrogen is great for helping grass grow quickly, but only if there’s enough water available for it to absorb into its roots. If not, the excess nitrogen will just wash off into storm drains or groundwater sources causing pollution—or evaporate into the air as nitrous oxide which contributes to climate change!

Chinch Bug Damage

Chinch bugs are a type of pest that feed on the roots and stems of plants, including St. Augustine grass. They can cause significant damage to your lawn by compressing the plant’s tissue, which inhibits its ability to absorb water and nutrients. Chinch bugs are most active during the warmer months of the year and are often found in sandy soils. When populations of these pests are high, they can cause extensive damage over time.

How to Get Rid of Chinch Bugs:

To rid your yard of chinch bugs, use an insecticide designed specifically for this type of pest control (like Ortho Home Defense Max Lawn & Garden Insect Killer). Apply it according to package directions using a hose-end sprayer or watering can. Make sure you get into all those hidden areas where the bugs tend to congregate like under mulch edges or around tree trunks.

Overuse of Pesticides

Overuse of pesticides can lead to a yellowing of the grass. If you overuse pesticides, it kills the good bacteria in your soil, which has a direct effect on the health of your grass. The good bacteria help break down nutrients for the plants and create a healthy environment for them to grow. When you kill those good bacteria with pesticides, you’re essentially starving your lawn.

You can tell if your lawn has been over-treated with pesticides by looking at the roots and leaf color: if the leaves are turning yellow or brown, that’s not normal and could be an indication that something has gone wrong with your lawn care regimen.


Yellowing of your St Augustine grass could be caused by an infection with a fungus known as Large Patch. This fungus is mostly active during warmer months when there is excessive moisture.

Symptoms include the appearance of circular patches of dead or dying grass blades that have yellowish-brown coloration. These patches will slowly grow in size and may eventually cause the entire lawn to become yellowish-brown in coloration as well.


  • High rates of nitrogen fertilizer will cause the grass to grow quickly, which provides more food for the fungus to grow as well. Instead, apply only enough fertilizer to keep your grass healthy without causing it to grow too much. You should also avoid applying any type of fertilizer when rain is expected within 24 hours of application because rain can wash away nutrients before they have time to get absorbed by the roots.
  • Make sure that your sprinklers are programmed correctly so that they don’t water during rainy days or after dark (when temperatures are cooler). If watering is necessary during dry spells then do so only at night so that evaporation won’t occur from daytime temperatures being higher than those at night.
  • Keep mowing your lawn regularly so that the blades can keep cutting back any dead or dying grass from spreading the fungus further into healthy areas of the grass roots system.


So there you have it! We’ve talked about why St Augustine grass turns yellow, as well as what you can do to keep it from happening.

Hopefully this blog has helped you to better understand why St Augustine grass turns yellow in different conditions, and what you can do to prevent this from happening. If you have any questions or concerns, please leave them in the comments below!

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