This is a personal project, inspired by GAKU (蝶と睡蓮 with Blender and Grease Pencil), I think everyone should check his amazing job, it was incredible!
My main purpose was just practice using the Geometry Nodes, during the process, it took me quite a time to testing whether I should generate petals based on random vertices or aligned vertices. Random generation looked naturally but uncontrollable, so I add a circle vertices to align the petals, it was more easy to control the transform.
I think my solution is not very clever, if you have any better idea, please let me know in your reply!