The most important thing to know about moss in your lawn is that it is a symptom of an underlying problem with your lawn. There is no point in using a moss killer, unless you address the problem causing moss to grow and thrive in the first place.

The main causes of moss in your lawn are:
- Poor soil drainage: moss needs moisture to proliferate, so waterlogged areas will always develop moss. You will need to drain the area – if your soil is heavy clay – you will need to improve it with sand, organic matter and lime before you sew your grass seed.
- Poor soil quality: infertile or poorly drained soil will encourage moss growth with poor quality grass.  Build up the fertility of the lawn by top dressing in the autumn. When starting a lawn, use a good quality loam to avoid future problems. Very sandy soils will also need to be improved with organic matter.
- Shade: lack of light will cause poor grass growth, and allow moss to take over. Can the cause of the shade be eliminated? Can lower branches be removed from a shade causing tree? If not try using special lawn seed for shady lawns.
- Over acidity: if the ph of the soil is below 5.5 and the grass is sparse, with moss, woodrush and sheep’s sorrel taking over, then this could be your problem.  If all these signs are present then apply 2 oz of ground limestone per sq yard in the autumn or winter. If the signs are not present – Don’t lime! It will cause a lot of damage and your lawn will rapidly deteriorate if you apply lime to a lawn which does not need it!!
- Underfeeding: Feed regularly in the spring and early summer to keep the grass growing strongly.
- Drought: drought weakens the grass and gives moss a chance to take over. Always water the lawn in periods of drought – grey water (e.g. Washing up water, used bath water etc…) is the most environmentally sound option.
- A combination of the above

When you have tackled the underlying causes, you can use a moss killer e.g. lawn sand applied in late April/ May/ June or Bio moss killer in spring or autumn. After a couple of weeks rake out the dead moss and re-seed bare patches.

Always follow a good lawn care programme during the year. Check out ‘The Lawn Expert’ by Dr. D.G. Hessayon