Iron Sulphate: What is it and how do you use it?

Is your lawn looking a little tired, withered, and pale? Maybe you have spongy moss spreading across the surface of your soil? Perhaps your lawn just needs a little pick-me-up? Iron sulphate is the answer.

Iron boosts photosynthesis, producing a lawn deep in emerald green and kills off the moss that suffocates the grass’s roots.

This article is all about increasing the resistance of your lawn with iron sulphate. We explore how to apply it, when, and how much to use. With an appropriate regime, you can maximise the natural verdancy of your lawn while preventing moss and boosting the health of your grass.

What is Iron Sulfate?

Bowl of iron sulphate

Iron is an essential element for a healthy lawn. It boosts photosynthesis (the process that turns light energy into chemical energy for nutrition). During photosynthesis, the plant extracts minerals from the soil and makes sugars with the help of solar energy, carbon dioxide, and water.

This process increases the plant’s resilience and gives it its beautiful, deep green colour. Iron helps the grass plant extract energy from sunlight, so it’s wise to feed your lawn with an iron-rich fertiliser such as Iron Plus 2-in-1 Moss Killer and Fertiliser.

Iron sulphate (aka ferrous sulphate) is often referred to as a “trace element” (meaning it contains a minimal amount of metal). It is added to general fertiliser mixes, defined by their NPK values.

Without additional help, it’s unlikely that your soil contains enough iron to maximise the growth and vitality of your lawn.

What’s the difference between iron sulphate and ferrous sulphate?

In short: nothing. It’s the same thing. Iron sulphate is often called ferrous sulphate or sulphate of iron.

Chemically, iron sulphate is a salt with various applications – industrially, horticulturally, and even medically.

You might be prescribed ferrous sulphate as a dietary supplement to treat anaemia and iron deficiency. But we absolutely do NOT recommend snorting a line of garden-bound iron sulphate, as there may be other toxic compounds included in the mix!

If you have a blood iron deficiency, speak to your doctor; not your lawn expert!

What do you use iron sulfate for?

Long grass with a house in the background.

Iron sulphate has several uses and can be applied to your lawn throughout the growing season to bring energy and vitality to your lawn.

Lawn-bound products are usually supplied in powder or granulated form and are often included in general fertiliser mixes. The principal reasons for adding iron sulphate to your lawn are:

  • Boosting the nutrient levels of your lawn after the winter
  • Providing your lawn with a fresh, deep green glow
  • Improving resilience before scarifying
  • To combat moss

TIP: An accurate measure of iron sulfate kills moss in as little as four days.

Use it after winter

Your lawn has to endure a lot in the winter:

  • Rain, snow, and sleet
  • Low temperatures and frost
  • Minimal sunlight
  • Pests that burrow into the soil
  • Diseases and fungi

Iron sulphate increases resistance to all of the above, making it a very welcome addition after a long, hard winter.

Use it for a green lawn

Sometimes your lawn develops a yellow or brown tinge, often during periods of drought. Adding iron sulphate will restore the natural green glow of your grass within a week of application.

Iron sulphate for scarifying

Lawn in serious need of moss killer

Scarifying is the act of removing the moss and organic matter that builds up on your soil’s surface. Grass needs oxygen to thrive, but the thick thatch layer around the individual grass plants eventually suffocates the roots.

So, it’s advisable to scarify your lawn every couple of years.


Scarification is pretty harsh, and it initially wrecks the look of your lawn. You effectively rake the top surface of the soil away, removing the moss and dead organic matter, and it can make your lawn look very sorry for itself.


Apply iron sulphate a week before you plan to scarify. This will get the plants in good shape before you attack them with the rake. The iron sulphate increases the resilience of the plants and gives them a much better chance of bouncing back after scarification.

Fighting lawn moss with iron sulphate

Moss can be a harsh opponent for your lawn, and it can appear for various reasons. It could be that:

  • Your soil is too acidic
  • Your soil is water-logged
  • There’s too little sunlight
  • Your grass has been mown too short

And while iron sulphate doesn’t remedy the CAUSE, it does clear up the moss.

Some quick fixes, though:

  • If your soil is too acidic, add lime.
  • For water-logged soil, aerate it.
  • Gardens with very little sunlight, you might be better with a different grass type that thrives in the shade.
  • If you’re mowing your grass too short? Well – just stop cutting it so short!

Iron sulphate is super-effective against moss. The right amount kills moss within just four days!

After application, the moss turns from green to yellow or brown, which means that it’s dying off. This makes it easier to remove during scarifying, helping you restore your lawn to its former glory.


Iron sulphate can make your soil more acidic, which – of course – can promote new moss or weeds. So, after using iron sulphate, it’s advisable to add Lawn Lime to counteract the raised pH.

It’s a complex chemical balance, isn’t it!

How do I buy Iron Sulphate?

Well, this is where a little bit of controversy enters the conversation! You can buy iron sulphate in its pure form as a white powder. But the Royal Horticultural Society doesn’t recommend using pure iron sulphate on your lawn because it can actually blacken your grass if you add too much.

And there’s an odd legal issue with pure iron sulphate that prohibits its sale as a moss killer.

However, fertilisers with iron sulphate as its principal active ingredient (like 2-in-1 Moss Killer and Fertiliser) are fine. Make sure you follow the manufacturer’s instructions; you shouldn’t experience problems.

How to use iron sulphate

The easiest way to add iron to your lawn is to use a pre-mixed product. But if you have the pure stuff, you can mix it with sand or dissolve it in water.

Mixing with sand

Mix 2-3kg of product with 4-5kg of sand per 100m2. Spread the mixture over the lawn by hand or with a spreader.

Alternatively, use 29g per m2 if you’re using 2-in-1 Moss Killer and Fertiliser – no need to mix it with sand.

Dissolving in water

For 100m2, mix 60-250g (depending on conditions and soil pH) with 100 litres of water.

For a more manageable (and liftable) solution, use a 10-litre watering can. Fill it with water and add 6-25g (about half a cup) of iron sulphate.

Tip: Iron Sulfate can leave unsightly, brown, rusty stains. Therefore, wear old clothes and shoes.

When to spread iron sulphate on your lawn

A mobile phone with a calendar

Whenever you’re sprinkling powder or granules, it’s best to wait for a windless day; otherwise, your mix can spread into flower beds.

Iron powders stain concrete and floor tiles, so avoid contact with your patio or paths. If any dry product does make contact with paved surfaces, sweep it up before it gets wet.

Activate your product by lightly watering your lawn after applying. If there’s light rain forecast, you can wait until the shower – but avoid a day with heavy showers, as it can wash the iron sulphate away from the surface of your lawn.

You can apply iron throughout the year (avoiding June, July, and August).

Avoid walking on your lawn for seven days!

Iron powders can leave unsightly, brown or rusty-looking stains on clothes and shoes. After applying, you should see improvements in the appearance of your lawn within a couple of days, but it can still stain for up to seven days.

And, in some circumstances, standing on your grass causes a chemical reaction that leaves black footprints in the lawn.

Give your lawn time to absorb the product – at least seven days is recommended.

Is Iron Sulphate Toxic or Harmful to Animals?

Always read the instructions, but most iron-based garden products aren’t toxic or harmful to animals. Essentially, you’re applying natural minerals to your lawn, so it’s not like you’re adding harsh chemicals.

However, pets (and humans) shouldn’t eat iron sulphate, so ensure that you store your product correctly. All MOOWY products are supplied in resealable pouches, so just seal it up, and it will remain safe.

When is iron sulphate not suitable for a lawn?

You shouldn’t use iron products on a newly seeded lawn. Lawn seedlings younger than three months old are unable to absorb iron sulphate. If you sprinkle it on a young lawn, you’ll just increase the soil’s acidity, which is bad for your grass plants.

The advantages of MOOWY’s iron products

MOOWY’s 2-in-1 Moss Killer and Fertiliser comes ready-mixed, so there’s no need to dilute or mix with sand. It improves the cellular structure of your grass, increasing the resistance and helps tired winter grass recover in the spring.

You’ll see a colour boost within two days of application and a total transformation within a week. This all-in-one product contains an NPK ratio of 3:7:10, with added Magnesium Oxide for strengthened cell structure.

Ready to get started?

Are you ready to improve your lawn? View our range of grass seeds, fertilizers & kits and get everything you need for a perfect lawn.

If you have any questions about this article, please email us, and we’ll be happy to help!

5 reasons to create a lawn

A beautiful appearance

This is perhaps the most important reason for many people. If your lawn is in good condition, it is a real feast for the eyes. A beautiful, deep green lawn that feels soft to your bare feet, on which you can play and picnic. Isn’t that what everyone wants?

A playground for children and/or animals

Do you have (grand)children or pets? A lawn is a great place to let them run wild. Grass is resilient and can take a beating, so you don’t have to worry about your lawn being damaged immediately. And if your child accidentally falls over, it is a lot less painful on grass than on tiles. If you want to create a place where your children can play safely, consider a lawn. If you have enough space, you can combine it with a swing or a trampoline. 

Time well spent with quick results

Fair is fair: if you want a beautiful and healthy lawn, you have to work hard! After all, a lawn requires a lot of maintenance. Mowing, scarifying, sowing, fertilising and removing weeds are some of the tasks. But do you have green fingers, enjoy being outdoors and like chores that produce quick results? Then a lawn is for you! Would you like to know how best to maintain your lawn? Under tips & advice, you will find various articles on the most diverse lawn topics. 

Less water nuisance

More and more gardens are being tiled. But all it takes is one good downpour – and we get more and more of those in the Low Countries – and the garden is flooded. Tiling your garden prevents water from finding its way to the ground. Not only do you have to find a way to get rid of the rainwater, but the weight of the tiles can cause them to sink. If you have a lawn, rainwater has a great capacity to collect. It nourishes the soil and ensures that grass starts growing again and (re)acquires its green colour. 

Better for nature

This reason is an extension of the previous one, but I am deliberately mentioning it separately. With tiles in the garden or by laying artificial grass, you are already fighting the soil life. If you have a lawn, you stimulate biodiversity. Worms and beetles that live in the soil are food for birds. OK, a neatly mowed lawn offers no shelter and food for insects such as butterflies and bees, but you can attract these insects by letting (a part of) your lawn grow a little longer. This will give daisies and dandelions a chance to grow. This in turn is food for insects. Another good reason: longer grass is more resistant to drought and heat.


These are my tips. What is a reason for you to have a lawn? Comment in the comments. 

Watering your lawn: The Importance of your Garden Sprinkler

OK, let’s start with the million-dollar question: does my lawn REALLY need watering? Surely it rains enough in the UK to sustain the health and vitality of my grass? And do I need a garden sprinkler?

And – yes – we do get a fair amount of precipitation in the UK. Our climate is described as “temperate”, which means we get cool, wet winters and warm, wet summers.

But, one way or another,  the climate is changing. And we’re getting longer periods of warm weather with no rain, followed by warm weather and monsoon-like downpours that cause floods and all manner of disasters.

So, if your grass is less green than usual – or even yellow – it’s a good sign it needs a drink. But when, how much, and how often should you irrigate your lawn.

That’s why you’re here.

Why do we need to water our lawns manually?

A healthy lawn needs a robust root system, protecting it from drought and disease. A well-watered lawn has deep roots, making the grass more resistant to periods of drought.

So, if your lawn is a rich, deep green colour, the moisture level is probably OK.

But the tipping point is a narrow margin – if the blades become dull or turn yellow, it’s a sure sign it needs more water. And left for long enough, the grass will wilt, and the roots will die, creating a patchy lawn, which becomes a fertile environment for weeds.

Patches in your lawn provide the ideal conditions for your once beautiful lawn to become home to a wide range of invasive, ugly weeds.

Bad times.


Water at the first sign of dehydration. Even better still, prevent dehydration in the first place by using a sprinkler or a hose to regularly water your lawn.

The Best Time of Day to Water Your Lawn

In short, the morning is the best time to water your lawn.

The sun is low in the sky during the early morning, providing valuable time for the water to soak into the soil. If you leave it later, the sun will be stronger and the water evaporates, failing to penetrate the soil. And probably more importantly, exposing wet grass to the midday sun is likely to scorch or burn the leaves.

So, early morning is best, even though watering in the evening might feel like a good option.

Beware; it’s not!

If you water in the evening, your grass is likely to remain wet throughout the night – and that’s the perfect condition for fungi and disease. And you don’t want that.

Water in the morning

Water in the morning so that the water can soak deep into the soil.

Your soil type determines how long to run your garden sprinkler.

So, for how long should I water my garden, then?

Watering your garden using a garden sprinkler is probably the most time-efficient approach. However, calculating for how LONG to water depends on a range of variables – namely:

  • Your soil type – is it clay or sandy?
  • Your water pressure
  • Your garden sprinkler (or hose pipe)

Everyone’s water pressure is going to be different – if you live at the bottom of the hill, it’s likely to be better than if you live at the top of the hill, for example.

So, in order to measure the length of time you need to run your sprinkler, rush off and grab yourself an old tuna tin.

Yes – an old, empty (and cleaned) tuna tin. We’ll be channeling the spirit of Blue Peter later in the article!

I have clay soil. How long should I run my garden sprinkler?

Clay soil is good at retaining water, so – in general – you shouldn’t need to use your garden sprinkler too often.

As a rough guide, if the temperature is around 20ºC, run your sprinkler for approximately 30 minutes.

However, if the ambient temperature is 25ºC, water for 80 minutes. Alternatively, run the garden sprinkler for 2 hours if it’s scorching to help prevent your clay soil from drying out and becoming hard.

Hard, dry clay soil becomes resistant to water. Liquid just sits on the surface and takes longer to penetrate the soil.

So, don’t let it dry out.

What about watering sandy soil?

Sandy soil drains very well, which is both a gift and a curse. Most plants don’t enjoy sitting in soggy earth – it suffocates the roots. So, sandy soil CAN be good for some plants.

On the other hand, sandy soil doesn’t hold onto moisture like clay soil, and too much water running through it washes away the nutrients that your plants need to thrive.

So, sandy soil requires additional watering (and more regular fertilising) than clay soil.

As a general rule, run your sprinkler for at least one hour if the ambient temperature is 20ºC, and do this several times a week. If the mercury rises higher still, double the sprinkling time per 5 degrees.

In a heatwave, sandy soil needs around 3 hours of watering. Do this every other day.

How much water does my lawn need?

Grass needs 2.5-4 cm of water every week in spring, summer and autumn to remain beautifully healthy and green.

But how do you know how much water the lawn is getting?

Use a rain gauge. (Grab that old tuna can – this is where it comes into play!)

Use a rain gauge

A rain gauge

You can buy a rain gauge that measures how much rain your lawn receives. Or you make one from an old tuna can, which is roughly 2.5 cm deep. Make sure that the lid has been entirely disconnected.

Leave your rain gauge/tuna can in a clear, open spot either on or close to your lawn. If you collect 2.5-4 cm of rainwater every week, you are good; there’s no need to add more water.


If no rain is expected, you’ll need to find out how quickly your garden sprinkler delivers 2.5-4cm of water. This will vary based on your water pressure and the model of your garden sprinkler.

How to calculate the efficacy of your garden sprinkler

The scientific approach to identifying how LONG to run your sprinkler is to set your rain gauge within the scope of your sprinkler and let the sprinkler run. Set a timer and keep an eye on your gauge – when it’s full to 2.5cm, stop your timer.

That’s how long it takes to deliver precisely 2.5cm of water.

You could use several rain gauges set at varying distances from your sprinkler to get an average.

However, when the temperature is higher than usual, your lawn may need between 3 and 4cm of water.

Use this table to help calculate the volume of water to use.

Temperature Frequency Quantity (if there is no rain)
< 15ºC  –  –
15ºc – 20ºC 1x a week 25mm
20ºC – 25ºC 1x a week 30mm
25ºC – 30ºC 2x a week 20mm (each time)
> 30ºC 2x a week 25mm

Garden sprinkler or hosepipe?

You can water your lawn in two ways: manually or automatically.

We’ll explain the most commonly used tools for the job.

Watering with a garden hose

Hand holding a garden hose

If you water with a hosepipe, keep an eye on how long you water.

Disperse the spray evenly across the lawn by waving the spout of the wand slowly from left to right (and back again). Make sure you cover the whole lawn, focusing on the areas that look the driest.

Use your rain gauge to measure the amount of water as you go.

Hosepipe watering is the hands-on approach but it can be time-consuming.

Watering with a garden sprinkler

Sprinkler spraying the lawn

A garden sprinkler waters your lawn evenly, without forming puddles, so that the water is evenly distributed.

Sprinklers are especially suitable for square and rectangular lawns and – depending on the nozzle and your water pressure – can have a decent range. For example, our impact sprinkler with stabilising awl or impact sprinkler with feet have a maximum range of around 25 metres.

A garden sprinkler does most of the work for you, but you need to remember to set it to run.

Automatic sprinkling

The easiest way to ensure that your lawn gets the water it needs is to use an automatic garden sprinkler that you set up, and it runs by itself.

So, when you go on holiday for two weeks, you won’t come home to a dead lawn!

Watering with a fixed garden sprinkler system

Fixed garden sprinkler system

You can, of course, set up a permanent garden sprinkler system, with connecting pipes that are dug into the soil. You see this type of set-up in public gardens and the grounds of stately homes. This system often uses pop-up nozzles which rise when they’re sprinkling and sink below the surface of the lawn when they’re at rest.

If you’re opting for this setup, you’ll need to dig strips into your lawn for the water pipes and position the sprinklers at regular intervals across the garden.

Be extra careful when you scarify or mow your lawn with permanent sprinkler systems to make sure you don’t inadvertently cut through the water pipes below the surface of the lawn. To avoid this, set your sprinklers so that they pop up from the surface of the lawn and mark them with a flag – this way, you’ll know precisely where your popups are located, exercising extra care around those marked locations.

However, if you have a smaller garden, it’s easier to plump for the less permanent approach: connecting your sprinkler to your garden tap via a timer.

Watering with a drip hose

Drip hose system installed into flowerbed

A drip hose provides water for your grass and plants in a particularly economical way. Compared to other sprinkler systems, you could save up to 70% of the water you’d otherwise use; if you’re on a water meter, that will make a considerable difference to your bill.

A drip hose (aka a “bleed hose”) is made from a porous material that’s designed to leak when water runs through the pipe. You dig your drip hose into the earth and cover it over with topsoil – using a pressure regulator to monitor water flow.

Connected to a timer, a drip hose can automatically provide super-efficient water delivery.

Watering AFTER fertilising your lawn

A lawn not only needs moisture but also requires nutrition in the form of fertilisers. Most high-quality fertilisers come in slow-release granules. These are sprinkled onto the lawn’s surface and are ready to release nutrients into the soil – activated by watering.


Never fertilise when the grass is already wet – the grains will stick to the grass blades, which can cause leaf scorch.

TIP: A good watering strategy encourages your lawn’s roots to develop more deeply into the soil – encouraging better drought- and disease resistance.

Watering after sowing grass seed

Whether you’re laying grass seed for a brand new lawn or overseeding to encourage greater grass blade volume, you should water immediately after sowing. This helps the grass seed make contact with the soil – without soil contact, it won’t germinate.

Keep the soil moist for at least two weeks after sowing and continue for the following two weeks after germination to ensure optimal results.


It’s better to water lightly four times a day than to water heavily once a day; otherwise, the grass seed could wash away.

Garden Sprinkler: Irrigating newly laid turf

Laying new turf

Newly laid turf provides instant results – a brand new lawn in an afternoon. But for the sod to take root, you need to water daily for the first two weeks.

If the turf shows signs of dehydration, water it more regularly until it recovers – in the morning, afternoon, and evening.

Irrigating existing turf: developing a watering strategy

Overwatering your lawn makes the roots lazy: they remain shallow. You want the roots of your grass plants to seek the moisture deep within the soil. So, it’s essential to create a watering schedule that encourages root growth.

Deeper roots make your lawn more resistant to drought because they feed on the moisture that sits deeply underneath the soil surface.


Don’t water every day.

Water according to the table above. In general, it’s better to water once or twice a week as that will encourage the grass’s roots to burrow more deeply into the soil, searching for water.

Don’t water when rain is scheduled. Let nature do the work for you.

Watering your lawn during a drought

We’re no strangers to hosepipe bans in the UK. And as climate change takes hold, it’s becoming more and more important to conserve water.

If you’re looking for a greener way of irrigating your lawn, check out our great article about installing and using water butts that collect rainwater.

Remember: If the day has been sweltering (above 30ºC), water very lightly at the end of the afternoon to cool your lawn. Just make sure it has time to dry for the night!

Ready to get started? Or do you need more information?

Check out our list of great articles and blogs for tons of expert information about grass seed, fertilisers, scarifying products and accessories for the garden.

If you have any questions regarding this article, you can always email us; we’re always happy to help.