When you go into a managed forest you see a mass of tree trunks. Then at a certain point you look again. You realize they’re all in perfect rows. Clarity. Clarity of vision. What you’ve been looking at from the wrong angle and not seen at all. You labor, you sweat to see what you couldn’t see from that other perspective.
That's The Edge talking about finding a creative groove, but I really think it's applicable to Signs in a philosophical sense. The realization that the trees are in perfect rows is what happens at the end of the movie, and I think that's why it's not a contrived or lazy ending.