Moss can be a serious problem on croquet lawns. There are some 12,000 species of moss of which around 600 are found in the UK. But of these only three main groups (see below) are found in croquet lawns. A general assumption is that the invasion of moss is caused by acidic, waterlogged and compacted soil conditions. But some species favour chalky alkaline soils and others can be found on light sandy soils. A good example of this is Guildford and Godalming Croquet Club. When I was called in to advise I found four croquet lawns completely invaded by moss yet these lawns were sited on very free draining soil with no shade and normal acidity. In fact the lawns sit on 130ft of sand. The photographs show what I found. The main shot doesn't look too bad but as you will see from the close ups there was at least 50% moss and the grass that was present was mostly coarse and very under nourished. The moss was very spongy and about 25mm (1") thick.
Where moss is found it usually indicates some fundamental weakness in the turf. So just treating with moss killer isn’t sufficient, the causes also have to be addressed. Usually this is as simple as instigating a proper maintenance program which will create a healthy and vigorous sward. However it is not widely appreciated that moss actually crops twice a year producing masses of spores that are blown by the wind across a wide area. These spores will lie dormant waiting for the right conditions to germinate and start the whole process again. So to eradicate moss infestations it is vital to stop the fertilisation of the spores and this means killing the moss before fertilisation has taken place. The only herbicides that actually killed moss have been withdrawn from the market but the programmes that I provide include treatments that control and blacken moss thus preventing the production and fertilisation of spores. This treatment is carried out in the spring and autumn while moss is present.
This application of moss control in spring and autumn will stop the problem in its tracks if you have an effective nutrition programme. Aeration is also important as moss does not like open aerated soil. Scarifying will usually only remove about 10% of moss and can be quite damaging to fine turf, so I try to avoid that sort of aggressive process if possible.
The three main groups of moss found on croquet lawns are:
1/. Hypnum and Eurhynchium. These are fern like mosses and often make swards rather spongy.
2/. Ceratodon purpureus and Bryum. These are tufted mosses which are found on extremely acidic soils and known as "winter moss" because it appears in the autumn and vanishes in spring.
3/. Polytrichum. This group is has upright growth with fine hair like leaves (poly = many; thrix = hairs) but is not common on lawns except in particularly acidic soils.