moss grows where it is damp and slow to drain. you can use path clear type preparations or sweep with a very stiff brush.

We are suffering from this at work on our car park.... we found that lightly sprinkling with soda crystals in powder form has worked a treat. Not sure how safe it is around plants or for that matter the health and safety police but it seems to be effective.

Use a dilution of Jeyes Fluid and brush it on but it smells for weeks, or a product named Algon available in most Garden Centres either brush on, fine rose watering can, or most economically knapsack sprayer. Takes a couple of weeks to show results but clears moss and algae.

Dont soda crystals cause burns?

soda crystals can cause burns so it does have to be used with care.