"David Hare-Scott" wrote:
newbiegardener wrote:
In the past few weeks I have noticed that large areas of our gravel -
its a landscaped garden area turning green on top (sort of limey
colour).

Thought it might be the dog 'wee' but it seems to be in areas that he
never goes to.

Has anyone any ideas what might be causing this and if I can doing
anything to reverse/stop it?

it has been very wet/damp recently down here in the South West.

A photo would help but it's probably algae.

Algae is a water plant... the OP probably has moss growing. If the
green is appearing in the shady areas it is definitely moss. Use of
decorative gravel in shade in wet/damp climes is not a very good idea.