From the Super Mario Wiki
Petunia is a violet flower that lives in Flower Fields of Paper Mario. When she appears in the east of Flower Fields, Mario will see Monty Moles eating at her roots. She beseeches Mario to defeat them so they will not cause further damage. She loathes Monty Moles, calling them "jerks." These Monty Moles are tougher than the ones Mario found in Mt. Rugged, but they are not significantly more difficult than before. If Mario defeats them, she will give him the Magic Bean. In her area, Mario can find the Red Berry tree; each Red Berry recovers 5 HP.
Petunia feels that seeds should never be planted, because once they are, the plant is stuck in one place, which could suggest that Petunia herself hates being stuck in her place. Her idea of never planting a seed contradicts the necessity of the seeds to be planted and to grow into adult flowers like herself. The other flowers call her a "Seed Maniac".
Beyond Petunia's area is a well. It is never known who or what is inside the well. If the player throws in a Blue Berry, a Flower Saver Badge will pop out. If Mario throws in anything else and a Crazee Dayzee or Bzzap! will pop out.