Tu B'Shevat historically is the date for computing the annual tithes on fruit from the fruit trees in the land of Israel. One of four new years in the Jewish calendar, Tu B'Shevat is the new year for trees. In Israel most of the annual rainfall occurs by this time and the almond trees blossom in Yerushalayim.Tu B'Shevat is still the date for computing a new year for purposes of the orlah, the name for the tree in it's first 3 years, during which time it may not to be consumed or utilized.
Tu B'Shevat falls out 45 days before the first of the new month of Nissan. The "Torah Emet" explains that the seed of a tree needs 45 days to take root. 45 days after Tu B'Shevat comes the new moon of the month of Nissan, the month of Pesach, which marks our Exodus from Egypt. "Coming out of Egypt and slavery to a state of freedom is intimately connected to the transition of nature from a state of hibernation and inaction to one of rebirth and rejuvenation".(1)
45 is the numerical value of the Hebrew word for man, Adam. The verse in Devarim 20:19 tells us "man is a tree of the field". According to the Kabbalah, Tu B'Shevat is the date on which the Tree of Life (the central image in this great work of Jewish mysticism) itself is renewed.
There is no distinct mitzvah associated with Tu B'Shevat. "Rabbi Nachman of Bretslav taught that a person should pray for a beautiful Etrog for Sukkot on this day. In Kabalah, the etrog represents Malchut, this world, in it's redeemed state, as a perfect vessel for the revelation of Gd".(2) It is customary to eat a festive meal, a Tu B'Shevat Seder in which there are many fruits, especially, the fruits of the land of Israel, "... a Land of wheat, barley, grape, fig and pomegranate; a Land of the oil of olives and the honey of dates..." (Devarim 8:8-9). Students of the Holy Ari first formulated a Tu B'Shevat Seder in the mid 1500's.
Tu B'Shevat is a time of awakening, of process, it marks a beginning. Today the flow of life in the tree is renewed. "Who is wise, he who sees the 'nolad'. The Hebrew word nolad comes from the root 'to be born' and alludes to the sliver of the new moon. The basic idea is that the wise one is he or she who sees in the initial appearance of a situation that which will ultimately transpire. Like sap rising in the tree, may we remember that even if it is at first concealed from sight, the ultimate redemption will surely come like the blossoms of spring.(3)
Rut Maoz's Fruit Cake and Sarah Idit Schneider's Almond Pudding, two great Tu B'Shevat recipes.
Tree graphic from "The Secret Language of Symbols" by David Fontana p103
"A Still Small Voice" Sarah Yehudit Schneider
"The Book of Our Heritage" by Eliyahu Kitov
"Seasons of Joy" by Arthur Waskow
"Stalking Elijah" by Rodger Kamenetz
Chabad-Lubavitch's Week in Review Vol IX No 17 and Vol IX No 19
(1)"Shevet MiYehuda", by Rabbi Avraham ben Yehuda Leib Eiger translation from Betsalel Edwards
(2)Tu B'Shevat supplement from A Still Small Voice 1988 by Eliezer Shore
(3)"Spiritual Insights into the Holiday of Tu B'Shevat" by Rabbi Avraham Arieh Trugman