: Walking through the woods, thinking, and not speaking to any Ents?

He could have stayed put in Lorien if that was all that he wanted to do.

I think he was talking to every Ent he could find, firing their hearts (which he and Narya have a particular talent for) with resolve to end the threat of Saruman. He would have spoken to Treebeard, too, if the timing had not been so poor the first time that he met him. Then, before he could find Treebeard again, Merry and Pippin had accomplished his goal by proxy.

Note that, when Gandalf meets Aragorn and co., he knows that the Entmoot is in progress. Why would that be, if he isn't talking to the Ents?