In "World Without Us", by Alan Weisman, the main idea of this excerpt from Chapter 3, "The City Without Us" is C. Ailanthus trees are nearly impossible to eradicate once they gain a foothold.
In this book, Alan Weisman depicts the world without human beings. He then depicts New York without humans. Before maintenance people would yank Chinese Ailanthus seeds but in a world without humans they will become implacable invaders.