Maude says if she had to be a flower, she would be a sunflower. She enjoys the sunflowers appearance. Maude s response is that they not all alike. Each one is special and different. This shows Harold wants to fit in, but Maude respects and is in favor of him being an individualist.
Flowers resemble beauty, and life.
Maude loves nature and life. Yet, she respects the life cycle. Harold is the opposite. He wants to die and does not respect the cycle. It is ironic that the scene ends in a graveyard.