How to Mix Iron Sulphate For Your Lawn

How to Mix Iron Sulphate  For Your Lawn

Mixing Iron Sulphate For Lawns and Plants


Mixing iron sulphate for use in the garden on your lawn or plants is pretty straightforward.  Here we will look at mixing iron sulphate into a solution for spraying on the lawn or plants, though you can also apply iron sulphate dry, by hand, or using a spreader.  



All you need to get started is some TRADE FARM NI LTD Iron sulphate, a watering can or a sprayer, and some water. Gardeners use iron sulphate for treating lawns and feeding ericaceous plants.  Iron sulphate, also known as ferrous sulphate, is used as a fertiliser for lawns.  Grass really loves an iron tonic.  After applying iron to your lawn it will turn faded looking grass into a lush dark green lawn in no time.  It also helps harden the turf and prevent lawn disease.  


You can order our Green Glen iron sulphate from our website here.

You can order our GUARD-EN-FORCE iron sulphate from our website here.



If you prefer shopping from Amazon you can find our products here:

Green Glen Iron Sulphate on Amazon

Guard-en-Force Iron Sulphate On Amazon



Mixing the Iron  Sulphate



First of all, health and safety.  Iron sulphate is classed as an irritant.  I have used it for over 25 years, spreading it by hand at times, and have never felt irritation, nor had any issues with it.  So do not worry that it is a dangerous or toxic chemical. Iron sulphate is relatively safe and easy to use.

Some people do not like the feel of it, others do not like the iron ‘smell’ from it. It is unlikely to cause any health issues unless you swallow several grams of it or get it into your eyes.  If swallowed then seek medical advice.  If in your eyes then rinse thoroughly, and if necessary seek medical advice.

If you do not like the feel of iron sulphate then wear gloves, latex, rubber, nitrile etc when using it.  Iron sulphate can cause stains on hard surfaces, and it can also cause your fingernails to look dirty, so wearing gloves when mixing and applying iron sulphate is not a bad thing.  I've had black looking nails from using sulphate and its taken me 3 or 4 days to scrub them clean again.  Lesson learnt.  Wear gloves to keep hands fresh and clean when using ferrous sulphate.


As mentioned, iron sulphate can stain hard surfaces such as paving, stonework, bricks, concrete etc so be careful when mixing and applying.  It can also be carried on the soles of your footwear onto paths, paving, and floors so be careful of this aspect too.  Also watch out for pets, it may irritate their paws, they may also carry it onto wooden floors and stone tiles causing unwanted stains.


Now we have those points out of the way we can get on with the mixing process for iron sulphate.  You can mix it in a bucket or a can. You can mix directly into a watering can or sprayer.  


Iron sulphate mixes well with cold tap water or you may get it to mix a little better using some lukewarm water.  It is as simple as that.  Add the required amount of sulphate for the job to your can or bucket and mix the required amount of water into it, either cold or lukewarm, give it a good stir and you are ready to go to the application stage. 


How much do you need?  When you mix iron sulphate you have some calculations to make.  You can apply at a rate of between 1 gram per square metre to 5 grams per square metre.  A tip here is that a typical slightly heaped teaspoon is 5 grams.  


In most case 1 to 2 grams per square metre will suffice. I would recommend that you NEVER exceed 5 grams per square metre.  More than this can scorch the grass.  This will make the grass turn brown/black.   If this happens then adding plenty of water to the lawn for a few days and the grass will recover and soon come up in a lovely dark green colour.


So 2 grams per square metre is a good rate to mix at.  You want to mix this as 2 grams per square metre in 1 litre of water.  So if you were using a 9 litre watering can and mixed at this rate you would add 18 grams iron sulphate and mix into the 9 litres of water and then spray it over 9 square metres.  Then repeat, and repeat, to cover the remainder of you area as required. 


If you apply at more than 2 grams per square metre ( and remember it isn't good to go beyond 5 grams per metre ) you will still give the lawn a nice iron tonic and the grass will green up really well but any moss in the lawn will blacken.  A nice green lawn doesn't look so good with black patches.


What happens to the moss?  Well moss does not like the iron and it will turn black and die and cause unsightly patches in your lawn if you use sulphate at a rate of more than 2 grams per square metre.  So if you are trying to green up your grass just be aware that a stronger mix might cause issues if you have moss growing in the lawn.



If you need more info on various ways of using iron sulphate then a quick search of google should provide all the information that is required.


A quick recap.  Wear gloves, mix sulphate with water at a recommended rate of 2 grams per litre of water and apply per square metre. Do not inhale or ingest sulphate. Do not get in your eyes.  Water in well.  You can water again after applying sulphate which will help wash it into the soil quicker.  



Using Iron Sulphate as a Lawn Tonic to Green Up Grass



If your grass lacks colour, is a pale green, or indeed is even turning brown or yellow, then using using iron sulphate as a fertiliser or tonic is just what you need to improve the colour and encourage strong healthy grass growth.  Using ferrous sulphate as a lawn tonic is a simple process.  What may be more complicated would be explaining to your jealous neighbours how you have such lovely, lush, thick and healthy growth of dark green grass.  

It should be noted that applying iron sulphate in hot and dry conditions is not recommended. If applied in these conditions the sulphate can scorch the grass.  If applying in these conditions then always water well right after the application of the sulphate mixture.  Applying at a rate of 3 or more grams per square metre will blacken and kill any moss in the lawn. This black, dead moss will obviously have an impact on the lush green colour you are trying to achieve. The dead moss will then need to be scarified to improve the appearance of the grass. Applying at a rate of more than 5 grams per square metre will very likely cause scorching of the grass.  While this is something to be avoided accidents do happen. Do not worry about this unduly. Scorched grass from sulphate application will often recover within 2-3 weeks with a regular watering, leaving you with the lovely green grass you envisaged.

1KG of iron sulphate will cover quite a lot of lawn area.  Often it only takes 1 or 2 grams per square metre to green up grass to give it a healthy dark green colour.  To cover an area of 50 square metres you would need to use 1 or 2 grams per square metre. It is often best to do a small test area first, perhaps a couple of metres at a rate of 1 gram per metre to see the results. If the results are suitable then you can proceed to cover the lawn at a rate of 1 gram per metre. If you don’t think it has produced the desired results then up the rate to 2 grams per square metre. So 100 grams would cover 50 square metres.  Mixing is easy, just dissolve sulphate in water, preferably lukewarm water to help it dissolve, and then spray onto the lawn using either a sprayer or a watering can.  You can also apply iron sulphate dry. Read on below for more detailed instructions on spreading dry and mixing for application by sprayer.





Iron Sulphate as a Turf Hardener to Improve Disease Resistance


Using iron sulphate on a lawn will not just improve the colour and the healthy growth of grass, it will also harden the turf and make the lawn more resistant to disease such as fungal attacks. For turf hardening with sulphate it is recommended to mix the sulphate in lukewarm water and apply at a rate of 3 grams per square metre. For a 50 square metre lawn you would simply need to mix 150 grams of the sulphate and spray evenly across the lawn area.  Again, you can apply sulphate with a watering can, a sprayer or apply dry by hand or with spreader.  Please read on below for mixing and application instructions for each method and warnings for drawbacks when applying.



Iron Sulphate for Ericaceous Plants


Ericaceous plants are plants that don’t like growing in soils that contain lime. These plants include azaleas, rhododendrons, camellias, magnolias, conifers, and blueberry. They do not grow well in soils that have a high pH level, also known as an alkaline soil. If you grow these plants in an alkaline soil they may well develop yellow leaves, a condition often known as lime-induced chlorosis or iron chlorosis, and it is caused by a lack of chlorophyll. This in turn is due to several factors such as poor drainage, damaged roots and compacted roots, but more often due to high alkalinity of the soil and lack of nutrients in the soil.  Lack of iron is one of the most common defects of a soil that is high in alkalinity. The high alkaline soil prevents plants from absorbing nutrients which are essential and thus you end up with chlorosis.  

Iron sulphate can help plants that do not like high in lime or alkaline soil. It will help increase soil acidity levels and will enrich the soil and aid plants in the absorption of nutrients from the soil. To apply iron sulphate for ericaceous plants you should add the powder to the soil around the plants at a rate of between 15 grams and 30 grams per square metre, being careful not to allow the sulphate to touch the plant stems or leaves, and then fork the sulphate into the soil. You should apply this to the soil every 4-6 weeks to maintain the correct soil pH level for the plants.  Sulphate can be applied from March to September for ericaceous plants.  The soil should then be well watered after application.  In very dry or hot conditions it is best to water the soil before and after application of sulphate. You can also mix the sulphate in 1 or 2 litres of water and carefully apply to the soil around the plants, again being careful to avoid spraying onto stems or leaves directly. Water again after applying for best and safest results.




Iron Sulphate with Children and Pets

A very common question is about the use of iron sulphate with kids and pets on the grass. It is highly recommended that both children and pets are kept off treated areas for 3-4 days after application of iron sulphate.  Iron sulphate can be toxic if ingested in large amounts.  It therefore can be dangerous to pets who would eat grass. Not so dangerous to children then unless they also eat the grass. Iron sulphate is also classed as an irritant so there is a small chance it might irritate pet paws or kids if they are on the grass.  In our opinion both of these warnings are just a little bit on the safe side. There is more likely to be a greater risk of kids and pets getting onto the treated areas and then carrying sulphate onto paving or other hard surfaces where the sulphate will cause a rust coloured stain that is difficult to remove.

For children there is a small risk of irritation and an even smaller risk of ingesting sulphate. This should definitely be guarded against as a precaution and if possible do keep kids off treated areas for 4 days. Having said that, if the sulphate is applied and well watered into the ground after application the risks are greatly reduced.  There is no reason to panic or regard sulphate as a very dangerous substance. It is just advised to be careful about letting kids onto the grass, if you can prevent them doing so after applying sulphate then this is the safest approach. Even while sulphate is regarded as an irritant, I personally often apply it by hand and it does not cause me the slightest problem. This might not be the case for everyone however.

For pets there is a danger that it can irritate their paws. And for pets that eat at the grass it can be dangerous with a risk of ingesting a toxic amount of sulphate.  This is the same product which goes in iron sulphate tablets for low iron, but too much of it is toxic to both humans and animals. It is recommended to keep pets off treated areas for 4 days and ensure the treated area is well watered.



Iron Sulphate Warnings


Using iron sulphate at a rate of more than 2 grams per square metre can cause moss to turn an unsightly black colour. If you have moss in your lawn and are applying sulphate to give the grass a green up tonic then the black moss will have a detrimental effect on the colour you are trying to achieve. For a good lawn green up use iron sulphate at a maximum rate of 2 grams per square metre.

Using sulphate at a rate of more than 5 grams per square metre can scorch the grass.  If this occurs then the grass will usually recover if the lawn is watered well for the next 1-2 weeks. 

If you use sulphate to kill moss then this will leave patches in your lawn if the moss is widespread. You will have to reseed the lawn to fix the patches.

Iron sulphate should not be applied in hot, dry conditions. Lower doses applied in these conditions can scorch or burn the grass.  If applying in these conditions then always water the treated area with plenty of water. Iron sulphate is best applied in wet conditions which helps to water it into the soil.

Iron is an irritant and it can cause irritation through contact with both humans and pets. We have used it many times ourselves by handling it and never been irritated, though it can cause black stains under the fingernails.  Just because we have never suffered irritation does not mean this is the case for everyone.  It is recommended to wear latex, rubber, or nitrile gloves when using sulphate. If sulphate gets into your eyes then you should wash them out well with water.

Iron sulphate should not be swallowed as too much of it is toxic to both humans and animals. Do not eat sulphate and be careful when spreading that it does not blow back on you.  If concerned you should wear a mask. Do not allow kids or pets onto treated areas if they are likely to swallow sulphate.

Iron can stain hard surfaces.  Always be very careful about your patio areas, paving, fencing, stonework, etc. Iron sulphate will cause rust coloured stains on hard surfaces.  Do not let children or pets onto treated areas as they can carry sulphate onto hard surfaces and cause stains.

When using a watering can or sprayer it is possible that you will have drips after applying sulphate. These drips can drop onto your paving or patios as you carry the can or sprayer back to your shed or garage. If these drips fall on hard surfaces they will cause stains.  It is best practice to have a bin liner or something handy to put the watering can or sprayer inside to take it back to your house or garage etc. to prevent drips falling on surfaces you do not want stained.

In short, when using iron sulphate, we recommend that you wear gloves when mixing and applying, keep children and pets off treated areas for at least 4 days, use care to ensure only grass and lawn areas are sprayed, and always water treated areas well to ensure sulphate does not damage grass.



Iron Sulphate Mixing Instructions for Using Watering Can, Sprayer and Applying Dry


When mixing iron sulphate for use it is always best to dissolve in lukewarm water to aid mixing and avoid clumps forming. You can apply sulphate dry as a powder by hand. Obviously this makes it very difficult to calculate the exact mix you are applying. You do not want to apply more than 2 grams per square metre for lawn green up and no more than 5 grams per square metre at any one treatment. A slightly heaped teaspoon is approximately 5 grams, just like a spoonful of sugar. So you really want to be applying a half teaspoon for greening and full teaspoon for stronger treatment over one square metre. As you can see this is not an easy method for applying sulphate.  

For using iron sulphate with a watering can it is simple mathematics and easy to mix. Use 2 grams per square metre for grass greening applied with one litre of water.  So for 20 square metres you will need 40 grams of sulphate in 20 litres of water.  Usually this will be a standard 9 litre watering can, so you will need 9 litres of lukewarm water and 18 grams of sulphate for greening grass. Then apply this over 9 square metres, then repeat over the next 9 square metres with identical mix of 9 litres water and 18 grams of sulphate. Then mix another 4 grams sulphate in 2 litres of water to finish off the last 2 metre area.

Once you have covered the entire area with your mix in the watering can it does no harm at all to apply another covering of just water to help wash the sulphate into the soil.  

If you want to apply iron sulphate dry using a spreader this again is difficult to calculate as spreaders can all operate at different rates. Trial areas may be the best way to calculate the amount of sulphate that is spread over an area by weighing the amount put into the spreader and then weighing what remains in the spreader after covering a couple of metres. You still do not want to apply more than 5 grams per square metre as this may scorch the grass.  If this does happen watering the grass well for next week or so will enable it to recover completely, indeed, it will turn a lovely dark green colour once recovered.

 Applying iron sulphate with a sprayer is a different proposition. You will need to use a little bit of maths to calculate using with this method. First of all you will need to know whether you want to use for green up of the grass or for other purpose.  This will mean 2 grams per metre for greening and 4-5 grams per metre as the maximum treatment.

Secondly, you will then have to calculate the area you want to treat. Because you get a better coverage using a sprayer than you do with a watering can you will want to calculate the area to be treated. Then you should calculate how much area you cover with your sprayer.

If you use a 5 litre sprayer, for example, and spray just water onto your lawn, how far does it cover?  Supposing you do this with just water and it covers 60 square metres, then you want to apply this with 2 grams or 4-5 grams per metre according to your purpose. So you will have 60 x 2 grams for grass greening in 5 litres of water in the sprayer. Yes, simple as that. 120 grams of sulphate in the 5 litre sprayer and apply over 60 square metres. If it is for stronger treatment then obviously you want 60 x 4 grams in the 5 litres of water.  It is important that you spray with water first to see how far you cover if you do not already know this information.  Perhaps your sprayer of 5 litres covers 100 square metres, then you want 100 x 2 grams or 100 x 4 grams according to purpose. 

After you have applied by this sprayer method it is advised that you apply a final covering of just water to ensure that it is well watered into the soil.  You can also apply a covering of water before and after to make it a safer and more efficient application.



Cleaning Iron Sulphate Stains From Hard Surfaces


What do you do if you have had an accident and ended up with iron sulphate stains on your patio, paving, fences, etc?  Iron sulphate will stain hard surfaces and the rust coloured stains can be very difficult to remove so you should always apply carefully and prevent kids and animals from walking on the treated areas as they can carry the sulphate onto other surfaces.

If you have got sulphate stains then the first option to try is lemon juice or white vinegar. Before you start you should be aware that if these methods work you may end up with part of your surface then showing up as cleaner than the rest.

To try to remove sulphate stains cover the stained area with lemon juice or white vinegar and leave for a while. Normally 15 minutes should be enough. I have left it on overnight, then covered with another dose of juice the next and then got to work on it.

So cover with lemon juice or vinegar and leave for at least 15 minutes and then scrub with a hard or metal scrubbing brush in circular motions.  Then wash off with water. Usually this should remove the stains. As I mentioned, the drawback is you might have very clean patches to the rest of the surface.  So perhaps you will have to clean the whole area using the same method. You should be careful when applying lemon or vinegar to the area as it can damage nearby grass and plants if it gets on to them.

If this method does not succeed then you can try other chemical methods. You can use Trisodium Phosphate available from variety of places including  To use this chemical to clean iron stains wear gloves before mixing and applying as it can cause irritation to skin and eyes and can be toxic if inhaled or swallowed. Please always handle trisodium with care.  Mix 2 litres of hot water with 100ML of trisodium phosphate and dissolve completely.  Pour the solution onto the stains and leave for 30 minutes to allow the mix to penetrate the stains.  Then scrub in circular motions with a wire brush to remove the rust stains. Use a firm pressure to get at the stains. Then rinse the area with clean water and check the stains, if they have not been removed repeat the process. 


If iron sulphate is what you need for your lawn, for greening grass, or for killing moss, then you can order ferrous sulfate online now for quick and free delivery within the UK.





All that's left today is to give you this link to go and buy some iron sulphate today.  If you prefer shopping via your account on Ebay or Amazon you can find our TRADE FARM NI LTD, GREEN GLEN or GUARD-EN-FORCE products on there too. 





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Good day,

I am interested in using your product over Moss on my lawns. I have approx 1000 Sq Metres of lawn.

I would like to apply it in diluted liquid form, so wish to seek your advice on how best to apply using a Hose End sprayer,

Thank you

To Tom Mackay - I have used this iron sulphate to kill moss and it is an excellent product and the moss was dead inside 2 hours. How fast is that? It doesnt say moss on the label nor does it give instructions for using it against moss on the label but that I have heard from people is due to licensing laws. Apparently it costs about £500,000 to license it as a pesticide against moss. It is quite legal to use as a lawn tonic or grass greener. It kills moss as a side effect of that. It good for greening the grass though. And wink, wink, double the grass greening dose and it will take care of the moss for you. Using a hose end sprayer you asked about is not the best way to do it. It does not distribute the iron sulphate evenly. Also you will have to ensure the sulphate is already diluted into a solution to spray it at all. You would be much better to use a knapsack sprayer and calculate to use at a rate of about 4 grams per square metre. It never fails. I have been using this tradefarm ferrous sulphate on my lawn for 10 years now and it has never looked so good.

Hi. Please can you advise how much iron sulphate I would need in a 15 litre knapsack sprayer if I want to treat the moss in the lawn? I am aware that the moss will go black & can then be raked out. How long should it take for the lawn to regreen & the black to disapear please?

Many thanks