Moss Control


Blackening! What is this?


Good question Gordon....

Blackening refers to the 'blackening' effect some products have on turf. These products generally contain iron or ferrous sulphate, which when used at high rates will blacken (and kill) moss and if used in excess or in dry conditions will also blacken the grass. There are two groups of products containing iron sulphate.

Your Moss Killer* (containing ferrous sulphate), packaged and sold as a pesticide to kill moss, will have an application rate designed to do just that. However, if you applied it at half rate it more than likely would only damage the moss but would act as a very good green-up for the grass. It would therefore be more like a fertiliser than a moss killer!!

On the other hand, soluble ferrous sulphate* or high iron fertilisers* (containing ferrous sulphate) are packaged and sold as fertilisers and will fertilise, green and harden the grass against disease. However, were you to double the application rate it would start to blacken and kill the moss in exactly the same way as the Moss Killer does.

Concentrates the mind doesn't it?

*Lawnsmith Products in this FAQ:


Ferrous Sulphate & Autumn Fertiliser - Can I use them together?


I have quite a number of patches of moss on my lawn which I was planning to treat with Ferrous Sulphate (after reading excellent advice pages on your website).  I’m also thinking of starting a better lawn-care regime – probably the twice/year system you describe.  My question is ¦. if I am applying Ferrous Sulphate now to attack moss,  should I not apply Autumn feed also – or can the two products both be used together (or perhaps with a week or two between them).  Or would I be better only applying the Ferrous Sulphate now and commencing the lawn-care system in spring ?

Hi David

You can use ferrous sulphate and fertiliser at the same time as they do different jobs - the fertiliser feeds and ferrous sulphate strengthens the grass - the ferrous sulphate also weakens the moss. However, if you have a lot of moss the ferrous sulphate will turn the moss black leaving a visible mess for a few weeks. If your lawn is prone to moss doing this every couple of months over winter can control the problem, however, this only works if you don't already have a serious problem to begin with.

If your lawn care hasn't been up to scratch then the two most important things will be an autumn feed and putting the mowing height up near the top.

If the moss is very bad I'd plan on raking it out in April, treating the remnants of moss with ferrous sulphate followed by fertilising and overseeding to bring the lawn up to parr as quickly as possible. Read this on Moss Removal and the links at the bottom of the page. You can then start using ferrous sulphate next autumn through winter to control the moss and stop it taking over your lawn again. 


Safe way to kill moss


I want to kill the moss, but I don't want to kill my dog...

Hi Lana

Presuming you want to get rid of the moss as well then the first thing is to rake it out. Won't affect the dog at all.

The second thing is to spray what is left with a solution of ferrous sulphate. This is a naturally occuring salt and the only possibly side effects are that the grass will be a little saltier and rich in iron (as is spinach) should the dog decide to eat it.


Lawn Feed or kill moss - which comes first?


I wish to improve the quality and general appearance of  my two "patches of grass"  250sqm and 130sqm. Should I feed them first or attempt to kill the moss?


Good question and I've updated the information to give a clearer answer. If you read the following two pages which cover moss killing, moss removal and lawn recovery with grass seed and fertiliser you will know exactly what to do:


Upright Moss


I have a large front lawn which has a problem with a type of moss.  Its a coarse green growth that has star like leaves that grows in patches on the lawn.  I’ve looked it up on the internet and I think it is a variety called polytrichum.

The soil here is sandy and it may be acidic.  From the internet it advises the this polytrichum is most common in these conditions.  I have tried various moss treatments but none of them get rid of the moss.  Do you have a product that would assist to get rid of this moss.  If not is there any advice you could offer that would help. 

Thanks for your assistance.


You're quite right ; it's polytrichum aka 'upright moss' or 'christmas tree moss'.

The bad news is that it's not that easy to control with chemicals and you should consider improving the health of the lawn so that it is less prone to invasion. I suggest mowing, aeration and fertilisation is where you should start followed by scarifying and overseeding in autumn.

All the advice you need is on the site and fertiliser products are available in the Lawnsmith Shop.


What is the best sprayer nozzle?


Is there a bar with multiple nozzles for applying liquid fertilizers from a knapsack sprayer. If not what is the appropriate single nozzle to use? I want to apply FeSO4.


Yes there are but they a notoriously tricky and you'll rarely see a professional or green keeper using one.

The best nozzle to use is a deflector nozzle. They don't fit all sprayers though.




Buy Lawnsmith

Make life easy with our range of ‘golf course quality’ fertilisers, weed killers, grass seed and equipment

Lawnsmith TV

Step by step lawncare videos for all your lawn maintenance needs from feeding and weeding to de-mossing and de-thatching

Email lawn alerts

As they happen, Warnings and Advice on disease and managing extreme conditions.

Monthly lawn diary

Let us keep you up-to-date with our monthly diary of lawn tasks..

Back to the top of the page