Garden question

[frizzby]

I have recently laid some small white stones in the back garden but in the middle of it all there is a tree. I have now noticed that the stones surrounding this tree has started to turn green.

What is the cause of this and how do I get my stones back to their original whiteish colour ?

Thanks

[gen2]

In a word - algae.

The shade provided by the tree allows the stones to stay moist for long enough for algae such as pleurococcus to thrive and these are giving it a green colour.

The only permanent cure is to stop the stones staying damp. Under-patio heating works out a bit expensive, so if you live in a country that actually gets to see the sun on a regular basis, pruning back some of the branches will let it through more to dry the stones.

[Thunderbird+]

Hi frizzby,
The stones turning green, I guess is due to Algae growth which is a very primative form of plant life and is a natural process, which is more than likely due to the shade of the tree.
Every Boy-scout knows that moss and algae always grows on the north side of the tree, pretty good advice to avoid going round in circles if your lost in the woods!
If the stones are pebbles, you could try moving them around with a rake occaisionally,hence the old proverb 'A rolling stone gathers no moss' or 'grass dont grow on busy streets' If larger boulders, an occaisional scrub with a stiff brush/broom might do the trick, but any chemicals could harm the tree roots. Good Luck Tbird+