Cool things to do with hanahaki
Reverse the creation requirements. Hate hanahaki (objectively very funny. I loathe you so much my lungs are creating a sunflower about it.)
Make it common. Seasonal hanahaki (when it's more common, I think reducing the creation requirements makes sense. Keeping secrets means a few weeks of flower petals in the spring, and very tired school teachers)
Commit to it. If the creation requirement is unrequited love, then some characters may suffer more for the answer already being no, but others are relieved. Let a character who's confessed to get rid of roses three separate times be baffled by someone actually considering surgery.
Commit to it. Someone decides to get the surgery, but as soon as they make the choice to deprive the other person of any love at all because they don't get the kind they want back, the plant withers and goes away on its own. Because you stopped loving them. Commit to it. The character fakes the surgery anyway because they already decided to hurt the other person, and now they have an excuse for acting cold and uncaring. Commit to it.