Pokemon the Series: Ruby & Sapphire Season 601 Episode 7 Tree's a Crowd

On their way to the next Gym, Ash and his friends get lost in a wood, where they encounter a group of wild Treecko. One of the Treecko seems to be at odds with all the others. It is living in a huge tree that seems to be dying, and the other Treecko seem to think it should move on. Ash and Pikachu are moved by the Treecko's dedication and help it try to save its home. Of course, Team Rocket shows up, trying to catch Pikachu with the help of their new Cacnea, and Treecko helps chase them off. When morning comes, a huge fissure splits the tree and it crashes down, but its seedlings live on. Treecko starts a new life as well, traveling with Ash.