Moss in lawns

Moss information

Almost all gardeners and lawn care enthusiasts will suffer moss problems at some point, many will have to control it every year. It is true that moss is one of the most common and frustrating lawn care problems and can invade almost any type of lawn.

However moss is more common in neglected lawns, where the grass has been allowed to become thin and weak due to the lack of proper lawn maintenance.

Mosses have no root structure and are flowerless plants that rely on sufficient moisture being available to reproduce and spread.

Moss is most troublesome on lawns during the winter and spring months. During these seasons grass growth has virtually stopped and the days are damp and dull with fewer hours of sunlight and the lawn is basically neglected during these cold months. These conditions are ideal for moss to invade.

However by promoting a healthy lawn with good management practices you can help prevent the conditions that encourage moss to invade.

The causes of moss in lawns & turf

The conditions that moss favours are as follows:

• Poor surface drainage - Lawns and areas of turf that hold water and are prone to flooding encouraging fern and tufted type mosses.

• Lack of fertility or nutrients - Any lawn low in essential nutrients is likely to be thin and sparse with poor grass cover, perfect for moss to invade and spread.

• Acid soil conditions - Soils with a low pH encourage moss.

• Shaded lawns - Lawns which have trees, shrubs and buildings surrounding them can prevent light getting to the lawn. This is especially true during the winter when the sun is low and the daylight hours are shorter. This often leads to the lawn having poor grass coverage which leaves it susceptible to moss invasion.

• Mowing lawns too close - Mowing too closely scalps and weakens the sward resulting in thin grass coverage inviting moss into the lawn.

• Drought - Lack of irrigation during drought conditions often leads to a degree of grass loss and bare patches appearing. If remedial action is not taken to restore grass coverage prior to the winter, then moss will invade.

• Compacted soils - These soils are likely to be in poor condition and will most likely be lacking in grass coverage, giving moss the ideal opportunity to invade.

• Excessive thatch layer - Any lawn that has an excessive layer of thatch is likely to suffer from moss. Thatch restricts root growth, prevents surface water drainage and dries out during drought, hardly a recipe for a healthy lawn.

Prevention & control of moss in lawns & turf

Moss is one of the most frustrating lawn problems in the spring time, however with the correct management program most of these problems can be avoided.

To prevent the invasion of moss you will need to address the problems and conditions that favour moss as outlined above. Addressing the following will help improve the quality of the lawn surface and help reduce moss problems:

• Improve the drainage - Improving the drainage of the lawn will help remove surface water quicker, thus keeping the surface drier and discouraging moss.

• Aeration - This task reduces soil compaction, promotes strong root growth, prevents thatch build up and creates a healthy growing environment for grass. This helps to suppress moss and eliminate other common problems such as weeds.

• Correct fertiliser program - Any lawn that receives a balanced fertiliser program will be healthy and vigorous with a thick coverage of grass, leaving little room for moss to invade.

• Reduce the shade - Reducing the shade by selective thinning and pruning allows more light onto the lawn. This in turn discourages 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. If you intent on mowing your lawn shorter than the norm, it would be beneficial to raise the height prior to the onset of winter to help create a stronger lawn and prevent moss.

• Irrigation - During dry periods water the lawn to maintain grass coverage and health. If there is little or no water available then lift the height of cut on the mower to relieve the drought stress on the grass.

• Take remedial action in the autumn - Occasionally lawns can suffer with grass loss during the summer for a number of reasons e.g. drought, chemical or fertiliser damage, animal damage etc. If this is the case with your lawn it is better to try and restore it to its former glory prior to the onset of winter to prevent moss invading.
  
  To accomplish this task, operations such as scarifying, aeration, overseeding, top dressing and feeding will have to be carried out. In fact these operation are not just for repairing the lawn, they should in fact be part of your autumn renovation plan that should be carried out each autumn to help prepare the lawn for winter and prevent moss.

• Prevent or reduce thatch - It is important that the thatch is kept in check with regular scarifying and aeration. Excessive thatch in the lawn will contribute to a host of problems, most which will encourage moss.

In a nutshell most of the above are essential maintenance tasks, which should be part of any lawn care program. They will create a healthy lawn free of moss and many other common problems such as disease and broad-leaved weeds.

Controlling moss with lawn sand

If for whatever reason moss does become a problem there a numerous ways to control it, the first method we will look at is with a product called lawn sand.

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. Lawn sand is a powder based product and is best applied through a spreader for an accurate application.

When applying lawn sand choose a still day, preferably when rain is forecast so it washes the product into the lawn.

Prior to applying any product through a spreader, make sure it is clean and working properly to avoid any problems such as overdosing or inaccurate application.

If possible apply the lawn sand to the lawn when the grass is dry. Apply the product to the lawn at the manufacturers recommended rates. Some people prefer to apply two applications, each at half the recommended rate, using the double pass method.

(Apply the lawn sand walking up and down the lawn, then apply the second application the same, but at a 90 degrees angle different from the first pass. This method help you apply the lawn sand more evenly and reduces an damage from overdosing.

Once the product has been applied it need washing in with in 48 hours thoroughly with water. It is important to keep people or machines off the lawn until it has been washed in.

Don't be alarmed if the lawn turns black as this is normal. After about 10 - 14 days the moss should have been killed and it is ready to be removed with a lawn rake or scarifier.

Controlling moss with sulphate of iron

As we have previously stated almost all moss killing products contain sulphate of iron. Sulphate of iron is readily available in both liquid and powder formulations. However both would be mixed with water and applied through a sprayer or watering can.

When mixing powdered sulphate of iron, it is better to mix it in hot water so it dissolves properly and does not clog the sprayer, as it is prone to this problem. Another problem with sulphate of iron is it can stain clothes, pathways and patios, so take care when handling and applying this product.

In most cases it may be more practical to use a liquid iron product to avoid the problems of mixing and possible clogging problems of the powdered product.

Please visit our Sulphate of Iron page for more info on moss control.

Other moss control products

There are a number of products available that will feed the lawn, kill the weeds and control the moss (Weed, feed and moss killer). These products save time as all three products are applied in a single application as opposed to three individual applications.

The only knock against these 3 in 1 products is moss control takes place during early spring and the ideal time for weed control is early summer, when growth is generally stronger and consistent, often yielding better results. However weed control results may still be acceptable during early spring, especially if plant growth is strong.

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 of moss 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 removing the dead moss, either a powered lawn rake or scarifier or a hand rake. Which one you choose will depend on the size of the area, the severity of the moss and the quantity of to be removed.

A lawn scarifier or rake is usually a petrol or electric powered machine that has a row of vertical blades or rakes. These blades or rakes rotate very quickly, slashing into the turf to remove the dead moss. In most cases a single pass is enough to remove the moss, however in severe cases a second pass, approximately 30 degrees different to the initial pass may be required.

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 moss will return again if the turf conditions are not corrected.