Mishna: Sukkah in a tree Asur D’rabanan, but nevertheless still Kosher. However, if 3 of the walls supported on the ground, may still go up and use Sukkah. We view the Tree “as if” it were not there. But how could you ignore the fact that you are still climbing up into a tree on Shabbos?! Since the Sukkah has the requisite Shiyur by itself with the 3 walls the Tree becomes TAFUL (Halachically insignificant) to the IKUR (main root) Sukkah.
cheap Premarin E’s Lesson: We must always remember that our physical bodies are our Taful and our soul is our Ikur, and live life remembering which should be in control of which.