I followed the tutorial by @schmeerlap here: http://www.planetside.co.uk/forums/index.php/topic,7733.0.html
After I had finished the steps I thought I would add some trees, however the trees are not showing up properly on final render so I wondered why this was???
Attached is the render and also my project file.
[attach=2]
See attachment. You can make the trees bigger there :)
Yay it worked.
Thanks :D