Always remember
That being said, the Lifebloom tooltip changed.
Old:
This effect can stack up to 3 times on the same target. Duration refreshed each time you cast Healing Touch or Regrowth on the target. Lifebloom can be active only on one target at a time, but all applications move to the new target when the target is changed if more than 2 sec duration remains.
New:
Duration refreshed by casting Regrowth or Healing Touch on the target. Lifebloom can be active only on one target at a time.
Tl;dr
All mentions of multiple stacks were removed.