Nature is trying to kill us all. Hell, nature is even trying to kill itself. But these trees won't go down without a fight. Like this one, that grew over the stump of another tree. That stump rotted away and this tree doesn't notice or, more likely, doesn't care.
You ever get sloshed with your friends and one of them starts to fall? They do that 40 yard stumble fall where you keep swearing they're about to topple over but never do? Turns out we learned that from nature.
This is a mutually beneficial relationship. The tree grew up through the sign and has a place to keep itself propped up. Meanwhile, the sign has pleasant shrubbery to gaze upon, so no one can say they didn't see this when they're speeding through the neighborhood.