What does the tree symbolize in A Separate Peace?

Trees are often symbols of life as they are planted on
Arbor Day to symbolize new life and beginnings.  For Gene, jumping on the limbs becomes
an issue of jealousy and envy in his life to the point of competition.  By jostling the
limb, Gene sends Phineas crashing downward and the jealousy ends as Gene and Phineas
become codependent.  No longer does Finny cast a shadow over Gene's life; the tree "is
weary from age."

While at Devon, Gene feels the shadow of
Finny and realizes that the enemy has been himself.  Blaming Finny for his
problems, Gene has cast a shadow from the tree of competition, over himself.  By
knocking Finny from the tree, Gene has tried to liberate himself from the competition of
Finny.  By returning to Devon, Gene has essayed to lift the shadow of guilt from
himself.