Tu B’Shevat, the 15th day of the Jewish month of Shevat, is a holiday also known as the New Year for Trees. The word “Tu” is not really a word; it is the number 15 in Hebrew, as if you were to call the Fourth of July “Iv July” (IV being 4 in Roman numerals). See Hebrew Alphabet for more information about using letters as numbers and why the number 15 is written this way.
Judaism has several different “new years.” This is not as strange a concept as it sounds at first blush; in America, we have the calendar year (January-December), the school year (September-June), and many businesses have fiscal years. It’s basically the same idea with the various Jewish new years.
Tu B’Shevat is the new year for the purpose of calculating the age of trees for tithing. See Lev. 19:23-25, which states that fruit from trees may not be eaten during the first three years; the fourth year’s fruit is for God, and after that, you can eat the fruit. Each tree is considered to have aged one year as of Tu B’Shevat, so if you planted a tree on Shevat 14, it begins its second year the next day, but if you plant a tree two days later, on Shevat 16, it does not reach its second year until the next Tu B’Shevat.
Tu B’Shevat is not mentioned in the Bible. There is only one reference to it in the Mishnah, and the only thing said there is that it is the new year for trees, and there is a dispute as to the proper date for the holiday (Beit Shammai said the proper day was the first of Shevat; Beit Hillel said the proper day was the 15th of Shevat. As usual, we follow Beit Hillel.)
In the Middle Ages, Tu B’Shevat 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 B’Shevat 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.
Dried fruit and almonds are traditionally eaten on Tu BiShvat
On Tu B’Shevat in 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 (Keren HaKayemet L’Israel). In the early 20th century, JNF devoted the day to planting eucalyptus trees to stop the plague of malaria in the Hula Valley. Today, JNF schedules major tree-planting events in large forests every Tu B’Shevat.
Tu B’Shevat is considered the Israeli Arbor Day, and it is often referred to by that name in the media. The kabbalistic Tu B’Shevat seder has been revived in Israel and is now celebrated by many religious and secular Jews. In the Hasidic community, some Jews pickle or candy the etrog (citron) from Sukkot and eat it on Tu B’Shevat. Some pray that they will be worthy of a beautiful etrog on the following Sukkot. Another custom is to eat a new fruit on this day.
In the diaspora, Tu B’Shevat became treated as the Jewish “Earth Day.” Ecological organizations in Israel and the diaspora have adopted the holiday to further environmental-awareness programs. On Israeli kibbutzim, Tu B’Shevat is celebrated as an agricultural holiday.
In keeping with the idea of Tu B’Shevat 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 B’Shevat in 1918, the Technion in 1925, and the Knesset in 1949.