The Buddha had many ways of teaching. One of the most treasured -- serving, according to Rhys Davids and other European scholars, as the basis of the world-famous Aesop's Fables -- are the Birth Stories or Jataka Tales.
These fables with talking animals and moral lessons present helpful, higher truths in ways we can grasp more directly than technical analyses, such as those found in the Abhidharma, or recited sutras, that tend to repeat a great deal, which is great for hearing but not great for reading.
Trees, indeed, can talk. That is, the dryads or elemental "shining ones" (earthbound devas) capable of inhabiting them can. Apart from these forest inhabitants or fairies, trees have other ways of communicating with one another, their environment, and humans.