There's a self-pick flower stand in a field next to the train station in Edingen (a small town in Germany between Heidelberg and Mannheim). Somebody plants flowers pretty much continuously during the warm weather season, and people can just clip them from the garden and put money in a metal box. Seems to work surprisingly well (or at least I've never seen them all vanish). Of course the trains which pass through the town are also on the honor system (I've had my ticket checked less than once per year).