How to Get Rid of Moss in Your Lawn

Moss is one of the most common lawn problems in the UK. Killing it is easy, but unless you fix the underlying causes, it will keep coming back. Here is how to deal with it properly.

Why does moss grow in lawns?

Moss thrives where grass struggles. The most common causes are:

• Shade: Grass needs light. Under trees or next to buildings, moss often wins.
• Poor drainage: Waterlogged soil favours moss over grass.
• Compacted soil: Heavy use or clay soil stops roots growing properly.
• Low fertility: Weak, underfed grass cannot compete with moss.
• Mowing too short: Scalped grass is stressed and moss moves in.
• Thatch build-up: A thick layer of dead material holds moisture and encourages moss.

When to treat moss

The best times are spring (March to May) and autumn (September to November) when the grass is growing actively and can recover. Avoid treating in summer when the lawn may be dry and stressed, or in winter when growth has stopped.

Step 1: Apply a moss killer

Most lawn moss killers contain ferrous sulphate (iron sulphate). This blackens and kills the moss within a week or two. You can buy it as a liquid, granular product, or combined with lawn feed.

Apply according to the instructions and water it in if rain is not expected. The moss will turn black as it dies.

Step 2: Rake out the dead moss

Wait until the moss has turned black, usually 10 to 14 days after treatment. Then rake it out thoroughly with a spring-tine rake or use a powered scarifier. This is hard work but essential – leaving dead moss in the lawn just creates a mat that holds water.

The lawn will look rough after scarifying. This is normal and it will recover.

Step 3: Fix the underlying problems

If you skip this step, the moss will return. Address as many of the following as apply to your lawn:

• Improve drainage: Aerate the lawn with a fork or hollow-tine aerator. On heavy clay, consider adding sharp sand to the holes.
• Reduce shade: Prune overhanging branches or thin out shrubs to let more light reach the grass.
• Feed the lawn: A spring and autumn feed helps grass grow thickly and outcompete moss.
• Raise the mowing height: Do not cut below 25mm in summer or 40mm in spring and autumn.
• Overseed bare patches: Thick grass leaves no room for moss to establish.

What about moss in shady areas?

Some parts of the garden may be too shady for grass to thrive no matter what you do. In these areas, consider alternatives like shade-tolerant ground cover plants, bark mulch, or simply accepting that moss is the natural ground cover.

Can you prevent moss completely?

In the UK climate, some moss is almost inevitable, especially in autumn and winter. A healthy, well-maintained lawn will have less moss, but expecting none at all is unrealistic. Regular feeding, proper mowing and occasional aeration are the best long-term prevention.