Wormcasts and molehills

If these are a nuisance, drag a stiff brush around lawn to knock down the casts (and dry the grass). Some acidic fertilisers (eg lawn sand) deter worms (and moles, which feed on worms).

Moss

Moss invades when growing conditions for grass is less than ideal:

• Cutting lawn too short and weakening grass.
• Leaving grass to grow long, then cutting very short, which weakens plants.
• Shade.
• Lack of fertiliser.
• Compacted ground from walking/mowing when soil very wet.
• Waterlogging.