When George is at his low point, his daughter Zuzu shows him a flower she won at school. He's too distraught to appreciate it. A few petals fall off, and Zuzu sweetly asks him to fix it. George pretends to put them back on the flower, secretly putting them in his pocket.
Later, when he sees what the world would be like if he'd never existed, the petals disappear. When he comes back to reality, they're there again. He excitedly shouts, "Zuzu's petals!!! Zuzu's petals!!!" as he holds them. For George, they've become a token touchingly symbolizing all the love and life that wouldn't have existed if he'd never been born. The flowers represent life and reality.