Why Your St. Augustine Grass Is Turning Light Green

St. Augustine grass is a warm-season grass known for its dark green color and lush texture.

It is a popular grass in warm coastal areas of the Southeastern United States, and it grows well in sandy soils.

While St. Augustine grass is beautiful to look at, keeping it maintained tends to be rather difficult.

St. Augustine grass has pretty strict care requirements, and if they are not followed, your lawn may develop bare patches.

One of the most common issues with St. Augustine grass is its deep green color fading, but why does this happen?

The most common reasons for your St. Augustine grass to turn light green include root rot, a nematode infestation, a lack of nutrients, not enough sunlight, and not getting enough water. Luckily, some of these issues may be easily resolved, and the damage to your grass is reversible.

Keep reading to learn more about why your St. Augustine grass is turning light green and how to fix it.

why is my st augustine grass turning light green
Light green St. Augustine grass is a sign of some issues to take care of.

Your Grass Is Suffering From Root Rot

Take All Root Rot is a disease in which the pathogens are always in the grass roots, even if it is healthy.

The pathogen is released when the ground gets too wet or the grass becomes stressed.

One of the causes of stress on your lawn is cutting the grass too short.

Always follow the one-third rule by only cutting one-third of the length of your grass blades when you mow.

Patches of yellow or light green grass are the first sign of Take All Root Rot, followed by the roots turning white and developing black spots.

As the disease progresses, the grass will become thinner and eventually die.

Use a fungicide to lessen the effects of Take All Root Rot in your lawn, but it is only effective when the disease is still in the roots of the grass.

Since the disease is resistant to fungicides and there is no other treatment for it, you may need to completely remove the affected patches of grass to prevent the fungus from spreading to your healthy grass.

Your Lawn Has Nematodes

Another reason your St. Augustine grass turns pale green is a nematode infestation.

Nematodes damage your grass by attacking it at the roots, which causes your grass to become thin and pale.

If you think nematodes might be why your grass is changing color, you will need to have a soil sample tested.

Nematodes are very challenging to get rid of since there is no chemical solution to eliminate them.

The only way to deal with nematodes is to make your grass and soil healthy.

Raise your mowing height to 3-4″ inches tall, and water deeply but less often.

Add potassium and phosphorus to your soil to promote growth and a strong root system.

You can learn more about adding potassium to your lawn here.

Keep your lawn as healthy as possible, and when the nematodes lessen in numbers or go away, your lawn will be strong enough to make a full recovery.

Your Grass is Lacking Nutrients

A St. Augustine lawn needs nitrogen and iron to maintain its deep green color, especially if the soil is sandy.

Sandy soil tends to allow essential nutrients to drain too quickly, so your grass is not getting what it needs to stay healthy.

Without these vital nutrients, your grass will turn pale green or yellow.

A nitrogen deficiency will make your grass turn a yellowish or light green color.

Nitrogen is important because it helps with chlorophyll production, making plants green.

Using a slow-release, nitrogen-rich fertilizer will help your St. Augustine regain its vibrant green coloring.

Do not apply more than one pound of nitrogen per 1,000′ square feet in a month, or you will be putting too much nitrogen into your soil.

Milorganite is an excellent organic slow-release fertilizer, and it will give you a lush green lawn for the entire growing season.

Check out these tips for how to get your St. Augustine grass to grow thick.

A lack of iron will make your St. Augustine grass very pale green or yellow. 

This yellowing is also known as iron chlorosis.

It is a good idea to test the iron levels in your soil before adding a treatment to your lawn.

The soil test will tell you how severe the iron deficiency is in your lawn, so you will be able to add in the proper amount with an iron supplement treatment.

A liquid iron supplement, also known as ferrous sulfate, is diluted with water according to the instructions on the label.

In general, the ratio of the iron treatment is two ounces of liquid iron mixed with 3-5 gallons of water for every 1,000′ square feet of lawn.

You will need to measure your lawn to know the proper amount of iron treatment to mix up.

There Is Not Enough Sunlight On Your Yard

St. Augustine grass needs a lot of sunshine to stay healthy and retain its dark green color.

A lack of sun may cause your grass to turn light green, and it may eventually die off and leave bare spots on your lawn.

If your lawn does not receive enough sunlight, you may need to re-think your landscaping.

Trim any bushes or trees which may be blocking sunlight from shining onto your grass.

Consider getting a fence with spaces to let light through if you have a solid fence.

You may even need to cut down entire trees to give your lawn enough sunlight.

If cutting down trees or getting a new fence is not feasible for you, you may want to think about overseeding your lawn with shade-tolerant grass to fill in the bare spots where St. Augustine will not grow.

Ryegrass or a more shade-tolerant cultivar of St. Augustine grass are excellent choices for overseeding.

Learn if St. Augustine grass will grow in shade and how to help.

Your Grass Is Not Getting Enough Water

Your St. Augustine grass may be turning light green because it is not getting enough water.

It is crucial to achieve the correct balance when watering St. Augustine grass because it will fade if not getting enough water, but it is also very intolerant of overwatering.

If your grass is growing in sandy soil, you will need to add 1/2″ inch of water to your lawn twice per week to keep your grass healthy and green.

If there is a lot of clay in your soil, you will only need to water it until you see the water start to runoff, and then you will stop right away.

When the clay soil starts to absorb more water, you may start adding one inch of water to your lawn at each watering session.

To avoid overwatering your St. Augustine grass, wait until the leaves begin to curl, which signals they are just starting to get dry.