iron for grass

Can Too Much Iron Hurt Your Lawn?

We all want a lush green lawn that makes the neighbours stop and stare, and there is a simple way of doing this; making sure that the grass has the right nutrients. One of these is iron for grass growth. But what happens when you go over the top; can too much iron hurt your lawn? Let’s find out.

One of the most frequently used iron supplements for grass is Ironite and this contains high levels of minerals and nutrients that can be very beneficial to the health of your lawn.

But what does iron do for grass?

It will boost its growth and leave it looking much more lush and green. Before we move on to the effects of putting too much iron on lawns, let’s look at what this mineral can do for your grass:

  • In the autumn and winter months, your grass may be more susceptible to disease but using a good liquid iron for lawns could improve its resistance to these diseases, leaving it healthier at this vulnerable time.
  • The iron will also make your grass more hardy when faced with cold conditions. Depending on where you are in the world, winter can be pretty chilly and this can have a devastating effect on grass that has not been treated with iron.
  • The increased acidity could reduce the activity of worms in the soil under the grass.
  • If you have problems with moss in your lawn, iron is a great way to kill this. It will turn it black and make it easier to remove.

However, there is such a thing as too much of a good thing and without a doubt, you can apply too much iron for your grass to handle.

When you put too much iron in grass this can cause burning and while most iron fertilisers will claim that they don’t burn the grass, going too heavy certainly will be damaging. Primarily, you should consider that using iron in extreme temperatures over about 26-27ºc or when the grass is very wet could have the opposite effect than you intended. That being said, you do need a fair amount of ground moisture so this is a delicate process.

Furthermore, when you are adding iron to your lawn in excess, it will do the reverse of what it should do, preventing your grass from growing properly.

Additionally, you should consider the effects the iron can have on other parts of your garden. These solutions will often stain hard surfaces so you must use it wil caution. Furthermore, they may also be damaging to your garden plants, staining them at best, killing them at worst.

When using these products, it is best to stick to the guidelines supplied on the packaging. However, if you are still unsure, we would recommend sticking to one pound of iron per 100m² of grass. This applies to established lawns and once applied, you will need to water the iron in for the best results.

Iron Deficiency In Lawn: Causes And Diagnosis

Your lawn is a living, breathing thing and while it is possible to have too much iron in the grass, it is also possible for iron deficiency in lawns to be an issue. In this case, finding the right iron supplement for your grass is essential. But first, you need to be sure that an iron deficiency is the problem.

While most well-maintained lawns won’t have problems with iron or any other nutrient deficiencies, it is also important to point out that altering the iron level of the grass, may result in problems with other nutrients. One of the best ways to determine whether iron deficiency is the problem is to send soil samples off for testing, this will give you an absolute answer. In the meantime, you should also make sure that other problems are not causing the symptoms in your lawn.

In the case of an iron deficiency in your lawn, you would notice that any new blades coming through are pale yellow in colour rather than being a rich green that you would expect. There are lots of reasons that your lawn may be suffering with this problem.

Most commonly, iron deficiencies in lawns are seen in new house builds where a new lawn is struggling to become properly established. This can be caused by the pH levels in the soil not being properly balanced or there may be a lot of sand in the soil. Furthermore, this problem can be caused by excess rain or water as this can wash away nutrients before the lawn has had the chance to absorb them. If you have been applying an iron solution and not seen any changes, it might be worth thinking about the recent weather.

When To Apply Iron To Your Lawn

If you’re asking yourself when to apply iron to your lawn, the most appropriate answer is when the weather is optimal. Too hot and the iron could burn, too much rain and it could be washed away. However, a balanced level of ground moisture is essential to help the lawn soak the iron up.

For this reason, most gardening experts would suggest that you stick to applying iron through the winter months when there is not too much chance of excess bright sun and the level of moisture will be better. However, this depends on your location as some parts of the world may have significantly warmer and drier winters than others.

How Often Can You Apply Iron To Your Lawn?

Many people are unsure of when to apply iron to lawn and grassed areas. In truth, there is no clear cut answer to this question. While the industry standards would dictate that treating areas with liquid iron for lawns every four to six weeks is sufficient, there are several factors to consider.

We mentioned earlier that your grass should not be too wet when applying iron for lawns, similarly you don’t want to apply it when the ground is bone dry either. Furthermore, how often you apply liquid iron for grass will depend on the iron levels in the soil and its pH.

For domestic lawns, applying iron once each season, equalling four times a year is the best approach to take. That being said, if the lawn is particularly deficient, you can apply it up to ten times each year. It is also worth considering that this supplement should not be used as a standalone fertiliser and is better when combined with your regular fertiliser as a complementary treatment.

Types Of Iron Fertiliser

There is more than one type of iron fertiliser for lawns so before you start applying, it is a good idea to understand the difference between these. This will help you to make a more informed decision on the best supplement for your lawn.

  • Ferrous sulphate is a common type of iron fertiliser that is also one of the most affordable. However, this is typically only suitable for lawns with a pH lower than 7, otherwise, it won’t have much of an effect. It contains around 20% iron.
  • Chelated iron for lawns is a compound that stabilises metal ions and protects the lawn against rain and oxidisation. These compounds contain various things including Fe+3, sodium, ammonia and amino acids or citrate.
  • FeEDTA is a type of iron fertiliser that does not work in alkaline lawns owing to its ineffectiveness in pH below 6.5.


Applying iron to your lawn can give it a serious health boost and improve its growth. But as with anything, you can go overboard and this could burn the grass. The best approach is to work out how often to put iron on your lawn and only follow the guidelines given by the manufacturer.

Further Reading:

Andrew Fisher

Andrew Fisher

Andrew is a dedicated father of three who really takes pride in his lawn and garden. You'll find Andrew behind the scenes of almost everything Edge Your Lawn produces. When he's not helping readers find all the information they need, he's in his backyard working on his lawn and garden landscaping. This year he hopes to build an outdoor deck and sort out his veg patches.

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