Okay so saved the game, was looking through my others saves and sure enough none of them were earlier than my foray out into the Fjord. But once I loaded my most recent save, the one I was able to run through the tree but not speak to him on before, suddenly now I cannot run through the tree anymore and I can speak to Yggdragsil.
End result, if you have this issue, fly off the island (I was still easily in sight of it in dragon form), save, then load your save and you should be able to speak with the tree.
