The picture isn't very appealing -- too many distractions. If the subject is truly the weeds -- wait for the train to pass - although that may still not be all that appealling and probably would not meet the challenge. I would have focused on the train and got rid of the weeds.
Based on you title, the weeds are the main subject in this photo. For me, I would like to see the weeds take a prominent place in the photo. I find that the pole is what me eye goes to the most.
I think this picture would have done better had the focus been more on the train rather than the weed. Also the rope or wire that runs up to the top left corner takes away from the image.
i'd preferred the plant in the front to be tack-sharp in focus, while maintaining the train in the back blurred. black n white doesnt seem to fit very well with this photo either.