Tu B'Shvat, the 15th of Shvat on the Jewish calendar, is the day that marks the beginning of a “new year” for trees. This is the season in which the earliest-blooming trees in the Land of Israel emerge from their winter sleep and begin a new fruit-bearing cycle.
Tu B'Shvat, 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 G-d, and after that, you can eat the fruit. Each tree is considered to have aged one year as of Tu B'Shvat, so if you planted a tree on Shvat 14, it begins its second year the next day, but if you plant a tree two days later, on Shvat 16, it does not reach its second year until the next Tu B'Shvat.
Prayers & Blessings
The blessing recited on fruit is:
Baruch Atah Adonai, Elohaynu melech ha'olam borei p’ri ha-etz.
Praised are You, Adonai our God, Sovereign of the Universe,
Creator of the fruit of the tree.
The Seven Spices
Of all kinds of trees, bushes, fruits and vegetables in Israel, seven species are mentioned in the bible as those with which Israel is blessed: wheat, barley, grapes, pomegranates, dates, figs and olives. One custom is to eat a new fruit on this day, or to eat from the Seven Species (shivat haminim) described in the Bible as being abundant in the land of Israel.
Today, environmental significance has come to play a large role in the celebration of Tu B'Shevat. Many have the tradition to plant trees, donate to environmental causes, dedicate themselves to a more environmentally conscious lifestyle, or simply spend a little time in nature among the trees.
Tu B'Shvat Seder
A feast including drinking both red and white wine, and eating Israeli fruits (such as figs, dates, nuts, etc.). The participants of this event read quotations from the bible in which the typical Israeli plants are mentioned, tell the history of the holiday, and sing songs about nature and trees in Israel.