Tu BiSh'vat is the New Year of the Trees. Its name is derived from its date on the Hebrew calendar.
In the Hebrew aleph-bet each letter has a numerical value. This system is called "gematria." The Hebrew "Tu" is made up of a tet, which has the value of nine, and a vov, which has the value of six. Together the two letters equal 15. Tu BiSh'vat occurs on the 15th day of the Hebrew month Sh'vat.
Tu BiSh'vat marked the time, determined by the sages, when the trees were nourished by the rains of the new year, as opposed to the rain of the previous year. Another name for Tu BiSh'vat is Rosh HaShanah L'Ilanotthe New Year of the Trees.Tradition teaches that on Tu BiSh'vat a heavenly court judges the trees and pronounces their fatewhich trees will thrive and which will wither.
In the days of the Temple in Jerusalem, taxes were collected on fruit trees. The age of the tree determined this tax, also called a tithe.Tu BiSh'vat was considered the birthday of the trees, and the age of the tree was reckoned from this date. When the Temple was destroyed, Tu BiSh'vat lost its purpose, since the laws of tithing and planting did not apply outside the land of Israel.
It was the kabbalists, the Jewish mystics of Safed, who created a new observance for Tu BiSh'vat some 400 years ago. Isaac Luria, a rabbi at that time, established the 15th of Shevat as a day for eating fruits. His intent was to connect humankind to nature. The kabbalists saw Tu BiSh'vat as a holiday that celebrated two ideas: the revival of nature after the long winter and the revival of the Jewish nation. They created a Tu BiSh'vat seder, similar in structure to the Passover seder.
The seder is a festive observance. Some common basic components of the seder include:
drinking four cups of wine or juice, which represent the seasons: white for the bleak time of winter, white with a bit of red to represent the earth's awakening in early spring, red with a bit of white representing the blossoming of late spring and dark red to represent the fullness of all the growing plants and vegetation along with the heat of summer
eating from three categories of fruit: fruits with a pit, fruits with a shell or peel, and fruits that are entirely edible
reading about nature, the earth, trees, the ingathering of the Jewish exiles, and the covenant of the people of Israel with God