Okay, this isn't officially growing in a gutter...but I suppose it could happen! This is the Decatur County Indiana Courthouse, and yes - there is a tree growin on/in the roof. I happened to drive past it last fall while out on a photo drive. I had not heard of it before, but apparently it's pretty well known. You can read more about it here: http://www.cityofgreensburg.com/history.html