Trees growing inside buildings in Baltimore, not only in abandoned structures but in the walls of some inhabited buildings:Trees Growing in Buildings
And here's a photo gallery of more building-invasive trees:Photo Gallery
As the reporter comments, "The trees are reminders that Baltimore was once a forest, and, if the trees had their way, would become one again."
My first thought upon reading that article in the Baltimore SUN was, "Wow, cool!" I can understand, however, that when large plants spring up inside the walls of inhabited structures and cause thousands of dollars worth of damage, the owners may not enjoy having their real estate transformed into the House of Usher.
It's amazing to contemplate how fast nature can overrun and consume the artifacts of humanity, especially in a wet climate such as a lot of North America. THE WORLD WITHOUT US, a book by Alan Weisman, describes in fascinating detail what an Earth devoid of our species would look like at various intervals after our disappearance. A few years ago there was a TV program on the same topic.
With the human population drastically reduced to a small fraction of its present level by some worldwide catastrophe, within a couple of generations the abandoned regions would have reverted to the wild. Much of the Earth in a postapocalyptic future such as S. M. Stirling's Emberverse or Jacqueline's Sime-Gen world prior to HOUSE OF ZEOR might look like that.
Margaret L. CarterCarter's Crypt