Before...

Opposite University College Falmouth's Woodlane campus, 21st June 2007. In case the sign's not quite clear, here's the text:

I do beg your pardon,
I am a guerilla garden.
Please do not mow,
I am trying to grow.

And after...

Same location, 3rd September 2007.

UPDATE: A garden-loving fox found this. Thanks, Taiga :) Apparently, the Falmouth Guerilla Gardeners had a blog.

For more info and links on Guerilla Gardening, here's the Wikipedia page. I'm quite liking the idea of moss graffiti; more of which, here, here, but not here or here (they're both great, though, much like that Little People blog).