The name Tu BiShvat is derived from the Hebrew date of the holiday, which occurs on the fifteenth day of Shevat. "Tu" stands for the Hebrew letters Tet and Vav, which together have the numerical value of 9 and 6, adding up to 15. The date may also be called "Ḥamisha Asar BiShvat".
Talmud
Tu BiShvat appears in the Mishnah in Tractate Rosh Hashanah as one of the four new years in the Jewish calendar. The discussion of when the New Year occurs was a source of debate among the rabbis, who argued:
The first of Nisan is the "new year for kings and festivals".
The first of Tishrei is the "new year for years", "for release years", jubilees, planting, and for the tithe of vegetables.
The first of Shevat is the "new year for trees" according to the school of Shammai; the school of Hillel, however, place this on the fifteenth of Shevat.
The rabbis ruled in favor of Hillel on this issue and the 15th of Shevat became the date for calculating the beginning of the agricultural cycle for the purpose of biblical tithes.
Biblical tithes
Orlah refers to a biblical prohibition on eating the fruit of trees produced during the first three years after they are planted.
Neta Reva'i refers to the biblical commandment to bring fourth-year fruit crops to Jerusalem as a tithe.
Maaser Sheni was a tithe which was collected in Jerusalem and Maaser Ani was a tithe given to the poor that were also calculated by whether the fruit ripened before or after Tu BiShvat.
Of the talmudic requirements for fruit trees which used Tu BiShvat as the cut-off date in the Hebrew calendar for calculating the age of a fruit-bearing tree, Orlah remains to this day in essentially the same form it had in talmudic times. In the Orthodox Jewish world, these practices are still observed today as part of Halacha, Jewish law. Fruit that ripened on a three-year-old tree before Tu BiShvat is considered orlah and is forbidden to eat, while fruit ripening on or after Tu BiShvat of the tree's third year is permitted. In the 1st, 2nd, 4th and 5th years of the Shmita cycle Maaser Sheni is observed today by a ceremony redeeming tithing obligations with a coin; in the 3rd and 6th years, Maaser Ani is substituted, and no coin is needed for redeeming it. Tu BiShvat is the cut-off date for determining to which year the tithes belong. Tu BiShvat falls on the 15th day of the Hebrew month of Shevat and begins a three-month series of holidays that occur on the mid-month full moons that culminate in Passover.
In the Middle Ages, Tu BiShvat was celebrated with a feast of fruits in keeping with the Mishnaic description of the holiday as a "New Year." In the 16th century, the kabbalist Rabbi Yitzchak Luria of Safed and his disciples instituted a Tu BiShvat seder in which the fruits and trees of the Land of Israel were given symbolic meaning. The main idea was that eating ten specific fruits and drinking four cups of wine in a specific order while reciting the appropriate blessings would bring human beings, and the world, closer to spiritual perfection. In Israel, the kabbalistic Tu BiShvat seder has been revived, and is now celebrated by many Jews, religious and secular. Special haggadot have been written for this purpose. In the Hasidic community, some Jews pickle or candy the etrog from Sukkot and eat it on Tu BiShvat. Some pray that they will be worthy of a beautiful etrog on the following Sukkot.
Customs in Israel
Tu BiShvat is the Israeli Arbor Day, and it is often referred to by that name in international media. Ecological organizations in Israel and the diaspora have adopted the holiday to further environmental-awareness programs. On Israeli kibbutzim, Tu BiShvat is celebrated as an agricultural holiday. On Tu BiShvat 1890, Rabbi Ze'ev Yavetz, one of the founders of the Mizrachi movement, took his students to plant trees in the agricultural colony of Zichron Yaakov. This custom was adopted in 1908 by the Jewish Teachers Union and later by the Jewish National Fund, established in 1901 to oversee land reclamation and afforestation of the Land of Israel. In the early 20th century, the Jewish National Fund devoted the day to planting eucalyptus trees to stop the plague of malaria in the Hula Valley; today the Fund schedules major tree-planting events in large forests every Tu BiShvat. Over a million Israelis take part in the Jewish National Fund's Tu BiShvat tree-planting activities. In keeping with the idea of Tu BiShvat marking the revival of nature, many of Israel's major institutions have chosen this day for their inauguration. The cornerstone-laying of the Hebrew University of Jerusalem took place on Tu BiShvat 1918; the Technion in Haifa, on Tu BiShvat 1925; and the Knesset, on Tu BiShvat 1949.
