I do not know the reason, but this photograph puts me in the spring mood...I know the branches are not covered in flowers (they aren't, right?, but the juxtaposition of that branch over the flowing water brings April in my mind.
You are correct, it's covered with moss and lichen (like everything here that doesn't move much). I liked the way that it stood out against the water below as I walked across the bridge. I like it more in the color version than in the b&w conversion (that nobody seems to care for). Thanks for your comment Julian!