The Cosmic Tree
The entire world of the Sefirot is often configured in two ways: the tree and Adam Kadmon, the primordial human. The symbol of the tree, which appears in Sefer HaBahir, is inverted (its roots are above and its branches are at the bottom). The “roots” of the tree, of course, are the highest Sefirot, which ultimately emanate from Ein Sof.
Pardes and the Garden of Eden
The symbol of the tree carries with it an association with Pardes, the orchard, which is an image used to convey mystical experience and knowledge. We also make the connection with the two trees specified in the Genesis story of the Garden of Eden, the Tree of Life and the Tree of Knowledge of good and evil. The Tree of Life itself is associated with the Sefirot of Tiferet (beauty) or Yesod (foundation), and the Tree of Knowledge is connected to Shekhinah (the Divine Presence).
There are four New Years in the Jewish calendar. The most familiar is Rosh Hashanah, occurring in September or October, which commemorates Creation. The fifteenth day of the Hebrew month of Sh'vat (called Tu B'Sh'vat) is the New Year for trees, which became an important holiday for Kabbalists because of the tree symbol in the Sefirot.
Kelipot: Blocking Divine Energy
The bark of the tree is its kelipah, meaning the outer covering that blocks the divine “light” from coming through. The idea of kelipot (plural of kelipah) interfering with the flow of divine energy is crucial in the Kabbalistic worldview. There were divergent views concerning the kelipot. Some Kabbalists spoke of ten kelipot, while others believed there were four, which they derived from the opening passage of Ezekiel's vision (1:4). Three of the four kelipot are essentially evil, but the fourth has the potential to become good or evil depending on our behavior. This is comparable to the coexistence of good and evil in the Tree of Knowledge.