Lawn Care Experts

Articles within the Moss Control and Removal Category

Unfortunately, if your lawn is prone to moss it will only get worse to the point where you have little or no grass left. You are, therefore, going to have to do something to tip the scales in favour of the grass.

The Causes of Moss in Lawns

Moss in a LawnIf you want a decent lawn then you need to help the grass and NOT help the moss – it’s LAWN CARE vs LAWN MOSS!

If the conditions in your lawn aren’t perfect, and they rarely are you may have a moss problem. In other words the natural balance in your lawn is towards moss and away from grass. Without any intervention the problem may get worse and, in some cases so bad that you have all moss and no grass!

There are three main causes of moss in lawns:

Lawn care practices

  • Scalping the lawn by mowing too close
  • Scalping high points because of a bumpy lawn
  • Infrequent grass cutting
  • Not following the ‘one third rule’ for mowing
  • Not aerating heavily used or compacted areas
  • Poor or inadequate use of fertiliser products
  • Not repairing damage from heavy use
  • Not removing leaves in autumn
  • Not removing excess thatch

‘Local’ environmental factors

  • Shady lawns
  • Clay soils or poor drainage
  • Poor air circulation and heavy dew
  • Dry areas such as lawn edges
  • North facing lawns
  • Acidic soil

Climatic factors

Ideal conditions for moss growth:

  • Wet climate (the West Country is usually wetter than the east)
  • Excess rainfall – 2006, 2007, 2008, winter 2014
  • Cloudy cool summers 2007, 2008, 2009, 2012

Poor conditions for grass growth:

  • Long hot summers 2003, 2004, 2006
  • Dry summers 2010
  • Cold dry spring 2010, 2013

As can be seen from the above, moss can grow in your lawn in quite a wide variety of conditions. The more suitable the conditions however, does not always mean more moss because lawn care practices can have the greater influence. A lawn scalped once a month with dull blades may well have moss even if it’s in a sunny dry location! The reverse may be true for a well maintained but slightly shady lawn.

Therefore, a lawn in an ideal environment with good lawn care practices will have little or no moss. The fact of the matter is that in this situation the grass thrives and the moss doesn’t get a look in. It is only when conditions turn against the grass such as permanent shade or mowing abuse that the grass is weakened and allows moss to take a hold.

It is no different for you. Have a few sleepless nights, over do the wine, boss on your back, over worked, stressed out and you soon feel out of sorts. And when you’re run down your health suffers and quite possibly you go and catch a cold! Not a lot different from your lawn catching moss!

Therefore, looking after your lawn, just like your health, is the most important thing in the war against moss.

Moss Prevention

If you knew that some of the things you do to your lawn are actually harming the grass and helping the moss I’m sure you would stop straight away if not sooner!

Mowing too close or scalping the lawn

Problem:Close Mowing can cause Moss Problems Scalping or mowing the lawn too close removes so much leaf that the grass can’t function properly and manufacture food. It may also damage the growth crown of the grass resulting in slow recovery or death. This damage also clears a space for the moss to move in to your lawn.

Solution: Keep the lawn mowing height above ¾” for all lawns other than ornamental ones. At this height or above the grass plant has plenty of leaf to function properly. If you still scalp because of bumps either remove the bumps or set the mower even higher.

If moss is particularly bad raise your mowing height up to 2”. This will mean the grass gets lots of light on its leaves and puts the lower growing moss in the shade.

Make sure that when you mow, the cut grass clears the moss by at least ½”. If you chop the grass off so that there is none showing above the moss you are killing your lawn.

Finally, in some situations, you cannot mow too high!

Not mowing often enough

Problem: Infrequent grass cutting (every 2-3 weeks) means that you let the grass grow too long before you cut it. You then cut perhaps two thirds of the grass off each time you mow. This shocks the grass which then stunts growth temporarily allowing moss to take advantage.

Solution: Mow the grass regularly – weekly if possible. This will cause the grass to spread sideways creating a denser lawn thus preventing the moss from moving in. If you follow the ‘one third rule’ – never remove more than one third of the grass height in any one cut – you won’t go far wrong.

Lawn compaction or poor aeration

Problem: Lawn compaction is a lack of air spaces between the particles of soil which means the soil holds no air and therefore cannot hold or drain water. The result is an unhealthy, lifeless and slow growing lawn.

Solution: If this problem is localised (around clothes line or kids goal posts) spike regularly with a lawn spiker, aerator shoes and hollow tine fork. Sometimes it may be too compacted to get the fork in so wait until it softens with rain, spike it, then keep it watered and spiked so it’s always firmish but not hard. See How to Aerate the Lawn.

If the problem is over the entire lawn then read our section on Lawn Aeration & Equipment

View Aerators

Trees and Leaves

Problem: The tree competes with your lawn for water and light in the summer and then covers it with leaves in the autumn. Leaves on the lawn for anything more than a few days will weaken and even kill the grass at a time when the moss is most virulent.

Solution: There is no easy solution, just clear the leaves at least once a week. If it’s dry use the mower to suck up the leaves. Other alternatives are a blower or rake. Leaves will always be easier to clear if you have kept your grass at the right height. There is nothing harder than raking wet leaves in long wet grass.

Lawn Fertiliser

Problem: If the grass is struggling because of a poorly fed soil then it cannot fight off a moss attack. Moss will grow quite happily on your driveway as it is used to low nutrient levels; therefore a hungry lawn becomes quite inviting.

Solution: Give your lawn at least one good feed a year in the spring. If you have a moss problem consider an autumn fertiliser or a winter fertiliser with iron to keep nutrient levels at their optimum.

See Fertiliser Range

Grass Damage

Problem: Many lawns are play areas and also access areas for greenhouses, gardens and clothes lines. Excessive wear and tear or use when the lawn is weak can damage or even kill the grass.

Solution: Where possible rotate areas of use (just like the cricket wicket is rotated) so a worn area is not damaged to the point of no return. If this is not practical be prepared to re-seed the area before the moss and weeds take over. Some areas may become compacted due to excessive or long term use. See Lawn Repair & Renovation.

Excess Thatch

Problem: The build up of thatch above ½” deep will start to reduce fertiliser and water penetration to the grass roots. This makes life difficult for the grass whilst providing good conditions for the moss.

Solution: A thatch layer up to ¼” is fine and actually beneficial but as in most things, you can have too much of a good thing! If too much lawn thatch is present it’s going to need removing by scarifying the lawn. For small to medium sized lawns or for just localised raking the rolling lawn raker scarifier is an excellent tool that requires little effort. This will also remove the majority of your existing moss as well so it’s two birds with one stone! See Lawn Scarifying & Raking.

Moss Control

Okay, so you’ve got too much moss in your lawn. Or is it that you’ve not enough grass? More than likely it’s one and the same so what to do about it?

Start by assessing the environment and natural factors that may contribute to your lawn being thin or unhealthy and therefore creating ideal conditions for moss growth.

Once you’ve done that, make as many of the following environmental changes as you can that are relevant to your lawns situation. Though this is not going to make the moss disappear it is a natural way to tip the scales in favour of the grass.

Shady lawns are prone to moss

Shady Lawn
Problem: For shade read poor light. Grass, like all plants needs light to photosynthesise (manufacture food). If it’s not getting enough light it is not getting enough food. Quite often shady areas will have tall but sparse grass that can look quite green. The grass naturally thins to allow each plant more light. The problem is ‘a few thin grass plants do not make a lawn!’

Solution: Reduce the shade if possible. If this is from buildings, walls or fences there is little that can be done. If however, the shade is from plants or trees things can be done.

For trees: make sure branches are two metres above lawn level. If the canopy is dense consider thinning it. If the tree has a preservation order please start by talking to a tree surgeon.

Bushes, hedges and plants: All by their very nature are dense and you wouldn’t want to thin them. However, consider reducing the overhang into the lawn and reducing the height.

Raise your mowing height. This means the grass traps more sunlight and puts the moss in even more shade. If the grass becomes thin try over seeding thin areas every spring with Lawnsmith® SHADYGREEN lawn seed for shady damp areas and Lawnsmith® STAYGREEN grass seed for dry shady areas.

Moss likes clay and wet soils

Problem: Grass like any plant needs air around the roots. This can be limited in clay or compacted soils. This is not ideal for the grass and it can become stressed and weak. Growth will be slow, colour poor and it won’t take long for moss to show. In addition, wet soils are often cooler than dry soils and this also reduces grass vigour.

Solution: You may be able to improve the drainage, or at least increase drainage in the top 2″ just by hollow tining the lawn. It may need doing every autumn depending on your soil and local environment.

To further improve the drainage in heavy clays it requires the addition of sand or a sandy soil mixture. Unfortunately you usually need so much that it becomes impractical. Hollow tining (coring) and brushing sand into the holes will make very little difference as the depth and density of the holes is usually inadequate. Top dressing with sand is also not the answer as the sand is on top when you need it below the clay soil to have any draining effect!

If the clay content is so high the only way is to start from scratch and rotovate a suitable free draining mixture into you existing soil after removing your old turf.

For large lawns an alternative may be to install drainage pipes. You’ll need a specialist drainage contractor for this as it’s not just a matter of putting in a bit of hardcore and a few pipes!

For small lawns putting drainage (a soak away) in the border(s) alongside the worst water logging area(s) can reduce the problem considerably. Go as deep as you can for best results.

If the grass becomes thin due to excess water try over seeding with  Lawnsmith® STAYGREEN grass seed. Though this seed is meant for dry and poor soils it tolerates extremes better than most grasses and may well be your best bet if you want grass!

Poor air circulation and heavy dew

Problem: Reduced air flow increases dew formation and delays its departure. This leaves the lawn permanently wet in spring or autumn. Wonderful for the moss but unhealthy for the lawn. It’s also a great environment for fungal diseases to attack and weaken your lawn still further.

Solution: If buildings and walls surround your lawn then not much can be done. If plantings prevent a breeze reaching your lawn then thin them a little particularly low down. Fences can also be a problem and if you plan to replace them use the variety that allows air to pass through them.

Dry areas and  lawn edges

Problem: A thin soil layer, or contact with stone (patio or driveway) can cause rapid drying of the lawn edges in warm or sunny weather. The grass then goes dormant and or dies due to the dryness! This allows moss to move in as soon as any moisture is available.

Solution: You need to prevent these areas drying by adding a heat barrier or keeping them well watered. See Lawn Edging.

North facing lawns

Problem: These are usually wetter, cooler and shadier than other areas. This means grass growth is often slow but moss growth is vigorous.

Solution: Raise your mowing height. This means the grass traps more light and puts the moss in even more shade.

You may also have to over-seed these lawns every spring because your lawn is in permanent shade from mid-autumn to mid-spring. Try over-seeding with Lawnsmith® SHADYGREEN mixture next time you scarify or rake your lawn.

Acidic soil

Problem: Most moss seems to prefer acidic conditions. This is also true of many of the fine grass varieties but the coarser grasses generally do not favour acidic conditions. As most soils are between a pH of 5.5 and 7.5 this is rarely the cause of moss problems.

Solution: Anything below a pH of 5 needs to have lime added. It’s best to apply this as ground limestone or dolomitic limestone which is slow acting, easy to spread through a fertiliser spreader and will not burn the grass.

Rarer still is a pH over 8. If this is the case it will be hard to lower and keep the pH lowered. I suggest overseeding with rye and smooth stalked meadow grasses which will do reasonably well in this pH. Our Classic Grass Seed will do well in these conditions.

Adapt your Lawn

Some things you just have to live with, so rather than making life difficult go with the flow and adapt a little.

Wet climate: Choose grasses that will put up with more water than most. Rye grass and tall fescues work well. Try over-seeding with our SHADYGREEN or STAYGREEN mixtures next time you scarify or rake your lawn.

Excess Rainfall: Periodically this happens so as soon as things get back to normal, rake out and over-seed any dead lawn areas before the moss and weeds take over.

Cloudy cool summers: Great for moss and some fungal diseases such as red-thread. A ‘hardening’ dose or two of Green-Up Ferrous Sulphate in the autumn will harden the grass and check the extra moss brought on by the weather. The lawn will look spectacular as well.

Long hot summers: Can do great harm to lawns. Grass has a great capacity to survive drought but over extended periods and perhaps with use of the lawn continuing, the grass plants may not survive. Even if they do, the chances are that when the rains arrive the moss will get going before your grass revives! You can help by over-seeding the lawn once the weather cools a little and moisture returns – usually August/September time.

View Grass Seed Mixtures

Moss Killer for Lawns

Using a moss killer is the next weapon to bring about a better lawn. Over the next few pages we will discuss the various ways you can control, kill and remove moss.

You can use moss killer as a standalone treatment to inhibit growth or as part of a moss removal programme. If the moss is not too overwhelming you can often keep it at bay or even reduce its spread by regular use of a moss killer.

Sulphate of Iron

Lawnsmith Green-Up Ferrous Sulphate
For all intents and purposes there is only one compound available that kills moss in lawns - sulphate of iron; also known as iron sulphate. Its chemical formula is FeSO4. It is the moss killing component of moss killers and lawn sand and is commonly sold in the green keeping industry as a fertiliser under the name of Ferrous Sulphate or Soluble Iron. It may also be combined with other elements and can therefore be used as a general fertiliser. Our high iron winter fertiliser called Winter Green is such a product.

The most common way of applying a ferrous sulphate based moss killer is to spray it in solution a week or two prior to raking out the moss. The moss is partially desiccated and is thus easier to remove. However, there are two other opportunities to use it that may make getting rid of moss easier and more efficient.

Use for Moss Suppression

Firstly we can use it to inhibit moss growth so that we enter spring with considerably less moss had we not taken action. By applying your iron sulphate moss killer, usually by sprayer or watering can during the moss growth period, anytime from late autumn through to spring you will at least kill the exposed upper layer of moss. Though iron sulphate is brilliant at killing moss it has its limitations when the moss is very deep. It will only penetrate 1 to 2cms into the moss so if you’ve got more depth than this the moss underneath may well remain alive. Therefore, if you know your lawn is prone to heavy moss infestations, starting your treatments in October before the moss gets too deep will be beneficial.

Even though the bottom layer of moss may remain alive, the killing of the top layer will stop light getting to the living bottom layer and the progress of the moss will be halted for perhaps 6 to 8 weeks. This is an easy and cost effective approach to moss control without the need for removal by raking, particularly if your lawn is not smothered. This treatment can be repeated every 4 to 8 weeks over the winter months.

If at the same time you have improved the local environmental factors a little, together with improved lawn care practices, you may well have made conditions more favourable for the grass. This together with a moss killer could bring about the desired result. If not, then the moss will have to be removed. See Moss Removal.

Use for Getting Rid of Moss

Secondly, you can use it after removal of the moss in the spring. Treating moss prior to removal will not kill all the moss; perhaps 20% to 50% will remain to re-infest your lawn. Therefore, if you treat what remains after raking you may well acheive upwards of 90% moss control. Ensure at least 4 weeks between applications if you are applying before and after raking. If you are overseeding, do this at least 24 hours after applying your moss killer.

Moss Killer Warning

Because ferrous sulphate acidifies the soil you MUST use it uniformly over the whole lawn otherwise you will create pH variations which will affect grass growth and may even increase moss infestations in future years.

View Winter Green See Moss Killer

What is Ferrous Sulphate?

Blackened Dead Moss in the LawnFerrous or iron sulfate (also spelled sulphate) is a constituent of garden and lawn moss killers and some fertilisers. It is exactly the same chemical compound regardless of how it is sold or used. They may vary slightly in concentration and be mixed with other compounds but apart from that they are the same.

Ferrous or Iron Sulphate as Moss Killer

If ferrous sulphate is to be sold as a moss killer then the law requires that it is covered by pesticide legislation plus extra health and safety measures just as any pesticide should be. This adds to the cost!

This enables the manufacturer to advertise the product as a moss killer and give directions for its use to achieve moss control. The concentrations are high enough to kill moss and low enough to cause the grass little or no damage. You will find these commonly sold as:

Moss Killer

This is either straight ferrous sulphate or perhaps with a little fertiliser added. Just basic ingredients and nothing unique or particularly scientific.

Lawn Sand

This is another method of applying ferrous sulphate to kill moss. This is just ferrous sulphate, with a dash of nitrogen fertiliser all mixed with sand to facilitate easy spreading.

If you have ever used Lawn Sand you may have experienced severe lawn damage as well. Unless kept dry, applied in the right conditions, evenly and at the correct dosage you can defoliate your lawn in days! I rarely use Lawn Sand because of this so unless you have the experience and confidence I suggest you give Lawn Sand a miss.

Ferrous or Iron Sulphate as Fertiliser

Ferrous sulphate as a fertiliser is the same stuff but sold for different purposes – usually for greening grass and hardening against frost and disease. The concentration to achieve this is usually lower than if used as a moss killer but pretty much every knowledgeable gardener and green keeper knows that it will do the same job as a moss killer at its higher permitted application rates.

Because it is not sold as a moss killer it is not required to be certified as a pesticide. This means it is cheaper but the benefit of being able to sell or market it as a moss killer is lost.

Granular Fertiliser

There are excellent winter fertilisers available that have very high iron content which cause blackening such a Lawnsmith® WINTER GREEN. These pass nicely through any fertiliser spreader and therefore pose no spreading problems. This is a slightly more costly iron option but the time saved, together with the fertiliser content easily make up for it.

If you like things as ‘hassle free’ as possible then this is the method for you: just follow the application details on the product. Rates at the upper end of the application rate scale will cause blackening.

Soluble Iron

You can also buy soluble iron or ferrous sulphate ‘as is’ and apply through a watering can with a weed & feed sprinkle bar or by knapsack sprayer. It is easy to get concentrations right, simple to apply, value for money and beneficial for the grass. Low concentrations give the lawn a superb green-up whilst higher concentrations ‘harden’ the turf against disease. Rates at the upper end of the scale will cause blackening. This is how most sports and commercial users apply ferrous sulphate whether as a fertiliser or moss killer. See the next page for more detail.

Fertiliser Moss Killer Sprayers & Accessories


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