What does Mellobloom's Healing Rose do?

One cast does two jobs: it tops up your side and leaves the enemy weaker for whatever comes next. That matches what Melobloom is for. She is a Grass-element support, and she fills that role in combat, including in Grass teams built around Irisalis.

Healing Rose is one of several ways she keeps a team standing. Her trait, Phantom Opening, grants a stack of Rose Mark when a party member deals basic attack damage. When that mark blooms after a target suffers three critical hits, it heals all nearby allies for 5% of her HP. She also cleanses debuffs and negative status effects from the whole team. Healing Rose is the piece that works the other way round: it puts a debuff on the opponent instead of clearing one from you.

To use it you need Melobloom herself. Budsquire evolves into her at level 27, and the evolution takes one Stamen of Kubo's Rose. Budsquire can also evolve into Thornblade, so make sure you are heading for the right branch before you spend the stamen.

Not settled: The skill has no stated heal amount, no named debuff and no listed EP cost, so you can't yet put a number on how much Healing Rose restores or exactly what it does to the opponent.