Subsequent to the destruction of the Temple, Tu Bishvat lost much of its relevance, but in the middle ages it was rediscovered by Jewish mystics. In the modern period it has enjoyed another revival as a holiday that links Jews with the land of Israel and as a Jewish celebration of the environment.

When the Temple stood in Jerusalem, Tu Bishvat served as the day on which farmers offered the first fruits of the trees they planted, after the trees had turned four years old. The following Tu Bishvat signified when the farmers were allowed to begin making use of the produce of the trees they planted, whether for personal or economic reasons.

In the middle ages, the Jewish mystics of Safed developed a ritual meal celebrated on Tu Bishvat that was modeled on the Passover seder. Four cups of wine were drunk and seven "fruits" symbolic of those of the Holy Land were eaten. With the rise of Zionism in the late 19th century, Tu Bishvat was rediscovered as a celebration that links the Jews with their land. The holiday became one of rededication to the ecology of the denuded land, with the planting of trees taking center stage in the celebration. Jews outside of Israel contribute money to plant trees there and/or plant trees in their own communities.

Ecology: With the increased concern for the environment in recent years, Tu Bishvat has taken on an additional meaning as a day on which Jews can express and act on their concern for the ecological well-being of the world in which we live. This has led to the rediscovery of the mystical Tu Bishvat seder, now transformed into a celebration of God's bounty and the environment.

Traditions: The name of this festival is actually its date: "Tu" is a pronunciation of the Hebrew letters for the number 15, and it falls in the Hebrew month of Shvat.

Traditionally, Tu Bishvat was not a Jewish festival. Rather, it marked an important date for Jewish farmers in ancient times. The Torah states, "When you enter the land [of Israel] and plant any tree for food, you shall regard its fruit as forbidden. Three years it shall be forbidden for you, not to be eaten" (Leviticus 19:23). The fruit of the fourth year was to be offered to the priests in the Temple as a gift of gratitude for the bounty of the land, and the fifth-year fruit--and all subsequent fruit--was finally for the farmer. This law, however, raised the question of how farmers were to mark the "birthday" of a tree. The Rabbis therefore established the 15th of the month of Shvat as a general "birthday" for all trees, regardless of when they were actually planted.

Fruit trees were awarded special status in the Torah because of their importance in sustaining life and as a symbol of God's divine favor. Even during times of war, God warns the Israelites, "When in your war against a city you have to besiege it a long time in order to capture it, you must not destroy its trees... Are trees of the field human to withdraw before you into the besieged city? Only trees that you know do not yield food may be destroyed" (Deuteronomy 20:19-20).

At a later time, the Rabbis of the Talmud established four "new years" throughout the Jewish calendar --- Rosh Hashana, or the Jewish New Year for the calendar date; a new year for establishing the reign of kings; a new year for tithing animals of Jewish farmers to be given to the Temple; and finally, Tu Bishvat, the new year for the trees (Mishnah, Rosh Hashanah 1:1). The Rabbis discussed why this date was chosen; saying that Tu Bishvat falls after mid-winter (usually in February), they concluded that the majority of the annual rainfall has usually already fallen by this time in the land of Israel, thus yielding a healthy, water-logged soil in which to plant new trees (Talmud, Rosh Hashanah 57a).

Practices: Tu Bishvat, or the "birthday" of all fruit trees, is a minor festival seemingly tailor-made for today's Jewish environmentalists. In fact, there is an ancient midrash (rabbinic teaching) that states, "When God led Adam around the Garden of Eden, God said, 'Look at My works. See how beautiful they are, how excellent! For your sake I created them all. See to it that you do not spoil or destroy My world--for if you do, there will be no one to repair it after you'" (Ecclesiastes Rabbah 7.13).

But it was not always this way. In ancient times, it was merely a date on the calendar that helped Jewish farmers establish exactly when they should bring their fourth-year produce of fruit from recently planted trees to the Temple as first-fruit offerings. After this, all subsequent fruit produced from these trees could be eaten or sold as desired.

Kabbalists: Tu Bishvat could easily have fallen into desuetude after the destruction of the Second Temple in 70 CE, since there was no longer a system of fruit offerings or Temple priests to receive them. However, the kabbalists or mystics of Tzfat  (city of Safed) in the Land of Israel in the 16th century created a new ritual to celebrate Tu Bishvat called the Feast of Fruits.

Modeled on the Passover seder, participants would read selections from the Hebrew Bible and Rabbinic literature, and eat fruits and nuts traditionally associated with the land of Israel. According to Deuteronomy 8:8, there are five fruits and two grains associated with Israel as a "land of wheat and barley, of vines, figs and pomegranates, a land of olive trees, and honey." The kabbalists also gave a prominent place to almonds in the Tu Bishvat seder, since the almond trees were believed to be the first of all trees in Israel to blossom. Carob, also known as bokser or St. John's bread, became another popular fruit to eat on Tu Bishvat, since it could survive the long trip from Israel to Jewish communities in Europe.

Participants in the kabbalistic seder would also drink four cups of wine: white wine (to symbolize winter), white with some red (a harbinger of the coming of spring); red with some white (early spring) and finally all red (spring and summer).

Modern Times: When Zionist pioneers began returning to the land of Israel in the late 19th century, Tu Bishvat became an opportunity for these ardent agrarians to celebrate the bounty of a restored ecology in Israel. In ancient times, the land of Israel was once fertile and well forested. Over centuries of repeated conquest, destructions, and desertification, Israel was denuded of trees. The early Zionists seized upon Tu Bishvat as an opportunity to celebrate their tree-planting efforts to restore the ecology of ancient Israel and as a symbol of renewed growth and flowering of the Jewish people returning to their ancestral homeland. In modern times, Tu Bishvat continues to be an opportunity for planting trees -- in Israel and elsewhere, wherever Jews live.

For environmentalists, Tu Bishvat is an ancient and authentic Jewish connection to contemporary ecological issues. The holiday is viewed as an appropriate occasion to educate Jews about their tradition's advocacy of responsible stewardship of God's creation, manifested in ecological activism. Tu Bishvat is an opportunity to raise awareness about and to care for the environment through the teaching of Jewish sources celebrating nature. It is also a day to focus on the environmental sensitivity of the Jewish tradition by planting trees wherever Jews may live.