By Tommm
United Kingdom 
can you identify a squidgey khaki-green substance on gravel?
It looks, for want of a description, like dead or boiled sea weed.
Slimey, it seems to dry up in sun then seems to revive in rain; so its more with me than not. Ive not had any before this year we have had gravel in the site for about forty years. Sphagnum type moss has ben growing in the gravel this year - its that wet - could that be a clue?
2 Sep, 2012
Answers
Did you drop any water retaining granules there by any chance? If so they could have soaked up water and got colonised by algae.
3 Sep, 2012
This question came up earlier this season on this site but as it (thankfully) didn't apply to my garden, I can't remember what the answer or treatment was nor can I quickly re-find it! Perhaps the weather conditions you've had in UK this Summer has made it more frequent since you haven't seen it before...? (or perhaps it's Those Aliens again? - sorry, being frivolous...) It sounds horrible, though...
I didn't join/read through questions till late Spring (2012) so try scrolling back through the questions from then - unless another less forgetful GOYer than I, can point you more helpfully as I'm sure they will!
4 Sep, 2012
Thanks you three algae it certainly is and it is likely that some water retaining material was dropped there when I cleared out the old compost from a trough.
I would like to know if there is anything that can be done to kill it short of having to pick it up by hand.
Will scroll back thanks
4 Sep, 2012
Looks like a sort of algae its this weather I,m sure.......
2 Sep, 2012