There are many important symbols in the book, but the most important one is the forest.  The title indicates this.  The forest symbolizes freedom to True Son.  He has been captured by the Delaware Indians from his White family, where he lived from age four to eleven.

The forest also contains a duality.  It is True Son’s struggle to decide which civilization he wants to be a part of.  Will he be an Indian, or return to the life of the White Man?

True Son had thought nothing could approach the joy of hunting in the forest.  But now he felt contentment in the deep summer days of the village. (p. 153)

In the end, True Son decides he is better off in the forest than among the Indians or the White Men.  He chooses his own path.