Moss is unsightly, and if left unchecked, can colonise a lawn in a short time, by winning the battle with the grass for the available nutrients, air and moisture. However, the main point to remember about moss is that it is merely the symptom of a problem, and not the problem itself. This may seem a strange statement to make, but the presence of moss is invariably an indication of poor growing conditions. It therefore follows that if those conditions can be improved, moss can be kept to a minimum. Simply killing moss and then scarifying it out is only part of the story; prevention is always better than a cure!

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The main reason that moss survives on lawns is that the surface of the turf has become compacted, and as a result the grass roots find it difficult to establish themselves properly in the hard ground. Moss, being shallow rooting, has no such problems, and furthermore is able to thrive on the layer of moisture on the surface which is unable to drain away. (See also Fact Sheet No. 1 - Aeration).

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However, there are a number of possible other causes:

• Shade on the lawn - most particularly through the winter

• Poor lawn nutrition - resulting in weak growth of grass

• Lack of density in the sward

• Mowing too closely - scalping is the main cause of cushion moss in domestic lawns

• Allowing the grass to grow too long can contribute to trailing moss colonisation

• Climatic conditions - mild, wet winters have seen an increase in moss in recent years

• Drought in the summer can cause moss in the autumn

 

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Treatment is therefore usually twofold; where possible, removing as many of the underlying causes (see above), and treating the moss with a chemical followed by scarification. In addition to removing the moss, scarifying removes the thatch which can impede drainage. Furthermore, scarification allows air to move more freely across the lawn; a major element in the construction of the new Wembley stadium is the ability of the roof to be reconfigured to allow air flow across the pitch, thereby increasing the health of the turf.

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Cultural controls include:

• Removal of thatch (scarification) - to improve drainage, and allow air flow across the base of the grass plant

• Thorough aeration - achieved by hollow-tine or solid-tine methods, to reduce surface compaction and improve drainage

• Removing causes of shade if possible, or, considering using a shade-tolerant strain of grass seed

• Improved lawn nutrition - to increase the strength of the grass, making the sward denser, which will eventually crowd out the moss

• Changing the height of the mower to avoid scalping 

• Top dressing - improving the drainage by addition of a sandy or gritty growing medium, especially after hollow tine aeration