The most effective moss control is best achieved by having a healthy and vigorous grass sward.  Increasingly mild and damp weather is adding to this troublesome moss problem in lawns.  There are basically three types of moss - upright moss, trailing moss and cushion moss and they all thrive when conditions are detrimental to healthy grass growth.

Waterlogged soil, as a result of poor drainage or compaction, prevents the free entry of air into the soil.  As a result there can be a build up of carbon dioxide in the soil that reduces the ability of the root systems uptake of nutrients.  The reproductive cycle of moss allows it to thrive in damp conditions, spring and autumn tend to be when colonisation takes place.

On the other hand moss also survives in conditions of low fertility, which might be quite dry.  Here it is a lack of nutrition that prevents the grass sward from being healthy thus allowing the ingress of moss or in extreme cases, lichens.

Moss thrives when grass is under stress.  Large trees and high hedges create moss conditions.  Deep shade, with excessive moisture dripping off the leaves is contributory factor.  In addition the root system of the trees and shrubs extract nutrient from the soil thus depriving the grasses of the plant food they need to thrive.  The reduced light levels conspire to inhibit grass vigour and allow the moss to compete.

Soils, which have become over acid, again favour moss as grass looses its vigour and ability to out compete the invader.

In summary, the occurrence of moss is a direct result of low plant vigour, low fertility, poor soil conditions or lack of available nutrient. All conspire to favour the growth of moss rather than of grass.

There are as number of products available for effective moss control, not least the traditional Lawn Sand mixture.  This is a product, which effectively burns off the moss while providing a boost to grass growth.  Sometimes more than one application will be required.

However, the best long-term strategy for moss control is through regular feeding to keep up the vigour of the sward.

Careful mowing is essential.  Removing excessive amounts of green foliage, more than 20% at any time, places the grass under great stress.  Stressed grass plants are more open to invasion from moss.  Equally leaving the grass excessively long will create a damp microclimate on the surface and will weaken the finer grasses.

Where possible the removal of over hanging branches and root pruning can prove highly beneficial.  Furthermore the reduction in height of hedges or opening up the gap in them will increase air movement and reduce shade – all of which will dry up the surface.

Mechanical treatments such as scarifying will remove considerable quantities of moss and if carried out in the spring and early autumn will be very effective.  This coupled with surface aeration designed to improve the surface drainage will go a long way to combat the problem.
The use of good quality top dressing doubles up in increasing fertility and helping create a drier more free draining surface.

Reducing acidity by the application of lime should be undertaken very cautiously as it may result in other problems.  The use of a product such as calcified seaweed would be a safer form of moss control.