Can Too Much Iron Kill Grass?

Can too much iron kill grass? Yes, Large quantities of iron are lethal for plants like moss and weeds, and can also be destructive for grass when used in high concentrations. An overuse of iron supplements can burn grass and cause discoloration, turning grass brown and occasionally black.

Iron is an important micronutrient for the constitution of your lawn. Iron is crucial for the production of chlorophyll, one of the essential ingredients for photosynthesis.

A lawn deficient in iron will result in the yellowing and eventual whitening of the grass blades, a condition known as iron chlorosis.

When applied correctly, iron can prevent chlorosis, boost the overall health of your lawn, and ensure a vivid, dark green color.

However, using too much iron on your lawn can result in the burning and browning of the grass blades, so it’s important to know how to apply it properly.

Using Ironite as your iron supplement of choice also runs the risk of burning your grass if used in excess.

Ironite contains iron sulfate, which may burn or discolor grass if used at a temperature of 80 degrees or higher.

Introducing too much iron into plants can also produce harmful effects by disrupting the photosynthesis process.

Unsettling the proper balance of iron needed for photosynthesis can hinder your lawn’s capacity to absorb the nutrients it needs to flourish.

How much is too much iron?

Iron is most often applied to lawns in the form of liquid, chelated iron, which will guarantee the most direct absorption of the micronutrient into the soil.

Chelated iron usually comes in the form of a spray, but can also be found as a powder. However, you may also choose to opt for certain fertilizers that contain a percentage of chelated iron along with micronutrients like nitrogen and phosphorus.

For a typical lawn, it is recommended to use 2 to 4 ounces of chelated iron for every 1000 square feet of grass.

Another option is to use Ironite, a product that distributes the micronutrient into the grass in the form of iron sulfate.

For this product, 1 pound should be used for every 100 square feet of grass. You can apply Ironite a maximum of 10 times per year.

Exceeding these quantity recommendations may result in the browning or burning of your grass.

It is also advised to keep iron products off any surfaces other than your lawn because iron tends to stain concrete, fences, and driveways.

How often should you put iron on your lawn?

After applying iron to your lawn, expect the color to fade after a few weeks in colder and damper conditions, and a few months in colder and drier conditions.

To maintain your desired color, repeat the iron application process every 4 to 6 weeks, depending on the pH level of your soil.

The more alkaline your soil is, the greater frequency with which iron supplements will need to be introduced.

How do I know if my lawn needs iron?

There are a few reasons why your lawn may develop iron chlorosis due to a deficiency in iron.

For example, using too much fertilizer can overload the soil of your lawn with too much phosphorus, which can impede the soil’s ability to absorb the necessary quantity of iron.

Your lawn may also have trouble absorbing iron if you’re working with alkaline soil or heavily compacted soil. Iron deficiencies are also common in lawns frequently exposed to cold weather, dryness, over-watering, and insufficient sunlight.

The easiest way to check your lawn for an iron deficiency is by simply assessing the color of the grass. If chlorosis has developed, you’ll notice an alteration in color.

The blades of grass will have lost their healthy green coloring, taking on instead a withered yellow look.

If the lawn is experiencing an acute case of chlorosis, the blades will turn completely white.

For a more extensive analysis of your lawn’s condition, you can perform a soil test to determine its pH levels.

A pH of 7 or higher means your soil is alkaline, while a pH lower than 7 points to acidic soil.

The ideal pH level for soil ranges from 6 to 7.

Alkaline soil above a pH of 7.5 will be at the greatest risk of an iron deficiency, so if your soil test results surpass this level you should consider applying an iron supplement to your lawn.


Using iron supplements on your lawn, when done correctly, can combat iron chlorosis and reinvigorate your lawn’s healthy green coloring.

It is important to note, however, that overusing chelated iron or Ironite can cause grass to burn and lose its color.

To prevent any damage, it’s best to stick with 2 to 4 ounces of chelated iron for every 1000 square feet of grass, and 1 pound of Ironite for every 100 square feet.

While the ability of your lawn to absorb iron is most dependent on the soil’s pH level, applying iron supplements to your lawn is a great way to restore and maintain its lush color.

FAQ Section

Can you apply ironite and fertilizer at the same time?

The best way to apply Ironite to your lawn is to combine it with fertilizer. The granular Ironite can be mixed in with a granulated fertilizer, and then dispersed onto the surface of the lawn at the same time.

Your lawn should be watered immediately after the application of your Ironite and fertilizer to ensure the proper absorption of the supplement into the soil.

How long does it take for iron to green up the lawn?

Chelated iron tends to produce faster and longer-lasting results, often deepening the green color of your lawn as quickly as 48 hours.

Ironite, while also an effective and cheaper product, usually requires at least a week and sometimes up to a month to come into full effect.

Also read

Nitrogen vs. Iron for Lawns

Milorganite vs. Scotts Turf Builder

Milorganite vs Ironite – Difference and Comparison

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