you might want to try searching for "nparticle falling leaves" on google as it is quite a popular tutorial topic. There are some interesting results and should bring you in the right direction.. you then could just swap the leaves with your flower models or instances!

Here are some results i found:
www.youtube.com/watch?v=bFTVa9Ec52Q — Gasket studio tutorial
https://area.autodesk.com/blogs/dunc..._paint_effects old but might be helpful for starting off!

just a tip, hope it helps