Just as Jewish tradition regards the first day of Tishrei as the New Year (Rosh ha-Shana) for mankind, so it regards the fifteenth day of Shvat as the New Year for trees. Tu B’Shvat – tu expresses the number fifteen in Hebrew – generally falls between mid-January and mid-February, and is celebrated in Israel by planting trees. Many American and European Jews observe the holiday by making contributions to the Jewish National Fund, which uses the funds to develop forests in Israel. The holiday, however, is an old one, predating the State of Israel by thousands of years.

Throughout the world, religious Jews strive to eat foods on Tu B’Shvat that are distinctive to, or characteristic of, the land of Israel, specifically the seven types of fruits and grains mentioned in Deuteronomy 8:8. When I was a child, my father used to bring home an Israeli-grown carob, a fruit with the decidedly un-Jewish name of St. John’s Bread. In Yiddish, it was known as buxer. Carob is incredibly hard and has little taste, though I have been told that if it is eaten right after falling from the tree, it is deliciously sweet.

Some Jews, basing practice on a tradition initiated by Jewish mystics (see Kabbalah) in the sixteenth century, make a special Seder on Tu B’Shvat, largely modeled on the structure on the Passover Seder: Four cups of wine, for example, are served during the meal. Thirteen biblical verses that speak of vegetation of Israel are read, and many different foods are blessed and eaten. Among the foods served at such a Seder are olives, dates, grapes, figs, pomegranates, apples, walnuts, carob fruit, pears, cherries, sunflower seeds, and peanuts. Currently, the Tu B’Shvat Seder is not widely observed; in recent years, however, it has become increasingly popular among mystically and ecologically oriented Jews.

 From Telushkin, Jewish Literacy