Druidic Growth is obtained once you have unlocked your first kingdom perk.
The documentation is not that clear on what it does.
"Druidic Growth - +3 Healing for Members when on Connected Kingdom Land"
Connected land basically means kingdom flags or obelisks
So far I have noticed two effects:
+3 healing when you are eating a berry
+3 healing to trodent doctrine
Sorry folks, it does not give you +3 healing while just standing around. Nevertheless it's a useful feature, imho. It's a tossup between this and private hunting for your first perk, if you do a lot of KD hunting.