I understand your confusion, you have to get a random encounter with one of the dryads (don't remember which one) twice before you can access their tiles. I understand that its obviously designed so that you encounter them after spending time completing quests in the early game, but if you are playing in save at level 6 with all of the old forest quests completed its kind of annoying to just spend a while walking around in circles till you trigger their encounters.
You have to meet Grainne first and she has a series of events that randomly proc while wandering the Old Forest. Explore a bunch or just walk a loop around the place until you've seen them all and you'll be able to explore the dryads' groves.
EDIT: Ninja'd!
EDIT: Ninja'd!
