How to control moss and algae in lawns

Author: Stefan Palm   Date Posted: 21 June 2023 

With all the rain around of late, combined with the predominantly cloudy days, you may have found moss and algae growing rampantly in your lawn and garden. When it comes to your lawn, moss and algae are not good companions and must be controlled asap!

During Winter, it’s not uncommon to see moss and algae growing through your lawn. While it may look OK, it can take over your lawn. The good news is that you can easily treat it, not only in your lawn but across all of your outside surfaces.

Winter is the time when moss and algae are most prevalent in lawns. This is because of the cool temperatures, the extra rain around and the lack of warmth to dry up surface moisture. Add cloud cover and shade into the picture, and all of a sudden, you have an irresistible environment for moss and algae to thrive in.

Moss and algae come in a variety of forms and love to grow in lawns. It can look innocent enough but can successfully out-compete a lawn in a short space of time. Left untreated, moss and algae can completely take over, especially where the lawn is weak or patchy. It does this by spreading underneath the lawn, occupying almost all of the soil space - eventually, the lawn simply gets crowded out. The good news is that it is relatively easy to get rid of; however, you will need to consider how to stop it from growing back.

Where and why do moss and algae grow?

Encroachment of moss and algae into lawns is usually the result of a combination of wet, shady and cold conditions, which is why it is most commonly noticed in Winter. In addition to this, they are most commonly associated with shallow, rocky soils, poor soil fertility, low soil pH (acid soils), heavy shade and poor drainage. If any of these factors limit turf growth, moss and algae can invade the lawn and establish a permanent residence.

How can it be managed?

Small patches of moss and algae in your lawn during the Winter are no big deal. It's when it starts to dominate that it becomes a problem.   I would recommend the following preventative measures to reduce the likelihood of moss and algae:

  • As much as possible, remove the conditions that moss and algae love to grow in. For example, solve any drainage issues so that moisture isn't lingering on the surface and introduce more sunlight. Have the lawn cored and consider topdressing with gypsum. 
  • Where possible, reduce the amount of shade present. This may include pruning tree canopies. 
  • For areas that receive heavy shade, introduce shade-tolerant varieties of lawn to maintain a good cover. 
  • Ensure that your lawn is as healthy as possible coming into winter. The patchier your lawn is, the more opportunity moss and algae will have to grow.  
  • Fertilise your lawn in Autumn since moss and algae prefer low nutrient levels.
  • Have your soil pH checked. If it's too acidic, correct it using garden lime. 

What can you do to treat it?

Where you have significant amounts of moss and algae, you'll need to remove it before it takes over your lawn. Try the following methods:

  • The safest and easiest way to control moss and algae in your lawn is with a product called Wet and Forget. It’s a liquid that you mix up and spray on. Wet and Forget is safe to use on lawns, pathways, furniture, timber, fibreglass, lawns, and the list goes on. All you need to do is spray it on and forget about it. It’s easy to use, it's safe, and it works.
  • A non-chemical alternative is to apply a combination of Iron Sulphate and gypsum. While toxic to moss and algae, your lawn will love it - you might even find that it greens it up during winter. Iron sulphate is best applied at the rate of 30g mixed with 70g of gypsum per square metre of area. Adding gypsum to the iron gives it some bulk, making it easier and safer to spread. Apply the mix evenly to a dry lawn and then water in after 12 hours and avoid overapplying. 1kg of this mix must cover at least 10 square metres; otherwise, you risk over-applying, which can damage your lawn. Avoid exposure to hard surfaces like pathways - it will leave nasty rust stains. The moss and algae should curl up their toes within seven days, at which time they can be raked off.  
  • Physically remove it with a rake or by hand. 

If you have a moss and algae problem that you can't seem to get on top of, give us a call on 8298 0555 or send an email to

Comments (4)

Wet and forget?

By: on 19 February 2024
Hi, just wanted to double check, have you actually tested that wet and forget product in lawn? (not the artificial of course) Does the grass survive that? Thanks

Paul Munns Instant Lawn Response
Hi Michael Thanks for your enquiry Yes, Wet and Forget can be used on Natural turf. Andrew

Algae + Moss

By: on 31 July 2023
I have a problem with moss an algae over the past 2 years I have used iron sulphate as directed for 2 years now with little affect, The moss grows in the open and in shade areas were as the Algae appears only in shaded areas, the moss just keeps coming back no matter what I do. nobody else is affected in my neighbourhood

Paul Munns Instant Lawn Response
Hi Max Thanks for your enquiry If the Iron Sulphate isn’t doing well for your area, I would recommend trying a product we have called Wet N Forget. We find this to be more affective. Thank you Andrew


By: on 23 July 2022
Will iron sulphate kill Moss at say 5g /meter as 40g/m seems very high

Paul Munns Instant Lawn Response
Hi Francis Thanks for your query If Iron sulphate is used at 5g/meter instead of 40g/meter it will be 1/8 less effective than the normal rate. I would recommend sticking to the 40g/meter Thank you Andrew

when to spray for moss

By: on 16 July 2021
As soon as this rain finishes is it ok to spray the lawn for moss?

Paul Munns Instant Lawn Response
Hi Kathy Thanks for your query Yes, it is ok to spray for Moss after it rains. Just wait for the lawn to be dry Thank you

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