Moss in lawns
A powered lawn scarifier is the perfect tool for removing
moss from the lawn. This operation would normally be carried out about 2 weeks
Moss is one of the most common and frustrating lawn care problems and can invade almost
any type of lawn, especially during the cold winter months.
However it is more common in neglected lawns, where the grass has been allowed to become thin
and weak due to poor lawn maintenance. Mosses have no root structure and are flowerless plants that
rely on sufficient moisture being available to reproduce and spread.
It is most troublesome on lawns during the winter months and into spring time. This is because
grass does not grow and light is lacking during the cold, dark winter months. Therefore with no
competition from the grass, moss takes the opportunity invade any weak areas on the lawn.
However by promoting a healthy lawn with good management practices you can help prevent the
conditions that encourage moss to invade.
Causes of moss
The conditions that moss favours are as follows:
- Poor surface drainage - This encourages fern and tufted type mosses.
- Lack of fertility or nutrients - Any lawn low in essential nutrients will
be thin and weak and open to invasion.
- Acid soil conditions - Soils with a low pH encourage moss.
- Shaded lawns - Lawns which lack light tend to have poor grass coverage
which leaves them open to invasion.
- Mowing lawns too close - Mowing too closely weakens the sward resulting in
thin grass coverage inviting moss into the lawn.
- Drought - Lack of irrigation during drought conditions causes to grass
coverage to suffer and moss can invade.
- Compacted soils - These soils are likely to be lacking in grass coverage
giving it the opportunity to invade.
Prevention & control of moss
To prevent the invasion of moss you will need to address the problems and conditions that
favour it as outlined above. Addressing the following will help improve the quality of the lawn
surface and help reduce the problems:
The above image shows a close up of
the lawn following moss treatment. Note that the moss has turned black and died and
it now ready to be removed with a lawn rake or scarifier.
- Improve the drainage - This will remove surface water keeping the surface
- Aeration - This reduces compaction and keeps the soil in good
- Correct fertiliser program - This promotes a healthy thick sward leaving
the moss with little opportunity to invade.
- Reduce the shade - Lets more light onto the lawn, again discouraging moss
which favours shaded areas with very little light.
- Raise the height of cut on the mower - Raising the height of the mower
reduces the stress on the grass and encourages a healthier sward.
- Irrigation - During dry periods water the lawn to maintain grass coverage
In a nutshell all of the above will help maintain a healthy grass sward which is the best way of
preventing moss becoming a problem on your lawn.
If for whatever reason it does become a problem there a couple of ways to control it, these are
- There are numerous products on the market available for the control of moss. Most of these
control products contain sulphate of iron.
The use of a product called lawn sand is the
traditional way of controlling moss in lawns. Lawn sand contains three ingredients
sulphate of ammonia, sulphate of iron and sand (sand is used
as a carrier). The sulphate of iron kills the moss and this ingredient can also be applied on
its own. The sulphate of ammonia is a nitrogen based fertiliser which will help with recovery
by encouraging growth. The ideal time for an application of lawn sand is in the spring time
when the grass is starting to show signs of growth after the winter months.
Other products available in both liquid and granular formulations are also available for the
control of moss. Most of these products will contain sulphate of iron plus some nitrogen to aid
recovery. There are many of these products available on the market, found in most good garden
centers. It is important to follow the manufactures recommendations when applying any product
used for moss control.
Please visit our Lawn sand or Sulphate of Iron pages for more info on moss control.
- The other control method is to use a chemical moss killer containing the ingredient
DICHLOROPHEN. This product gives a longer lasting kill than lawn sand and is usually applied
through a sprayer in liquid form. However this product may not be available much longer.
Lawn sand and sulphate of iron are applied with a spreader, these products are very light and
powdery so it is best to avoid windy conditions. Both lawn sand and sulphate of iron (if applied in
powder form) will need watering in after application.
Sulphate of iron can also be mixed with hot water into a solution and sprayed onto the lawn via
a sprayer. It is important to mix it thoroughly to prevent the sprayer becoming blocked.
Timing of moss control
The ideal time for any moss control is early spring when the grass is showing signs of growth
after the winter months. The grass needs to be growing to help any bare areas recover after the
moss has been killed and removed. If this is done to early you may end up with bare areas on your
lawn and the moss may invade your lawn again before the grass starts to grow.
Removal and aftercare
About 10 - 14 days after the moss treatment was applied, the moss should have been killed
and is now ready to be raked out of the lawn. There are two options for this task, either a
powered lawn rake or scarifier or a hand rake. Which one you
choose will depend on the size of the area and the quantity of to be removed.
|A powered lawn scarifier like the machine
in the above image is ideal for removing moss from the lawn. These machines are
designed for removing vast quantities of moss on larger areas of turf. For smaller
lawns a spring tine hand rake may be used to remove the moss, but they can be hard
work on a large lawn.
Once the moss has been removed it can be cleared away and you are ready for the next task. You
can now go ahead and over seed and top dress the bare areas (if necessary) from where the moss was
removed, this will help speed up recovery and thicken up the grass. Applying a nitrogen based
fertiliser afterwards will also help with recovery, however many types of moss killer products now
contain a fertiliser for this purpose.
To prevent any future problems keep your lawn in a healthy condition by correcting the causes of
moss as outlined above because it will return again if the conditions are favourable. Light
applications of sulphate of iron every 4 - 6 weeks throughout the winter months (October -
February) before moss becomes a problem will help prevent any moss invasion.