I wish it was that easy! Some flowering shrubs will sprout as seedlings and in my garden I do have a hardy hibiscus that popped up as a baby near the mother plant but this does not mean the new plant will be just like the mother or that it sprouted from a fallen flower. It could be there because of a root that traveled a bit then sprouted or from a seed husk dug into the ground by a squirrel. I am going to wait and see what it looks like in a few years when it is mature enough to bloom. You can try the same thing with fallen seed of your hibiscus but first you should let he flower fade and then the petals fall off and then keep the seed pod dry so it can mature a few more weeks before you try to plant it into the soil. Gardening is all about experimenting and part of the fun is you never know what will pop up. Keep growing, Marianne Binetti