The holiday of Tu Bishvat ("the fifteenth of Shvat") falls this year on Thursday, January 20. What are its origins, and when and why did it become incorporated into the calendar as the Jewish "Arbor Day"?
Shvat is the eleventh month of the Jewish year. Its name, meaning a staff or club, was introduced at the time of the return from Babylonian exile (6th century B.C.E.), and evokes the month's destructive rains. The earliest reference to the month's fifteenth day in particular appears in the Mishnah (Rosh Hashanah 1:1):
The new year for trees is marked on the first day of Shvat according to the school of Shammai, while according to the school of Hillel it occurs on the fifteenth of the month.
The rabbinic concept of a "new year" indicates the point at which accounts are due or settled. There are four such new years in every year, including the one known popularly as Rosh Hashanah, also called a "day of judgment." Another such accounting centers on the tithe that had to be paid on agricultural produce. Just as American taxes are assessed on income earned up to a particular point in time (December 31), it was necessary to establish a cutoff date for calculating the tithe on the previous year's crops.
The choice of the fifteenth of Shvat as that date is explained by the Talmud (Rosh Hashanah 14a) on the grounds of climate and weather: "[By then] most of the year's rain has fallen, even though most of the [winter] season has yet to occur." This requires a brief digression on the existential significance of rain in the land of Israel.
Describing that land to the Jewish people, Moses says (Deuteronomy 11: 10–12):
The land you are about to enter and settle is unlike the land of Egypt you have left, in which one could sow seeds and irrigate by foot, like a vegetable garden. The land you are going to settle is a land of mountains and valleys, which absorbs water as rain from heaven. It is a land that the Lord, your God, inquires of perpetually; His eyes are upon it from the start of the year until its close.
Unlike Egypt, which is irrigated by the overflow of the Nile, the land of Israel is totally dependent on rainfall, a resource not always available in sufficient quantity—a situation that has not changed to this day.
How, then, did the fifteenth of Shvat come to be identified as the point at which the winter rains had peaked? There are two answers: one "scientific" and the other speculative. The former, encapsulated in a responsum of R. Hayya Gaon (Baghdad; d. 1038), reveals an intimate knowledge of the climate of the land. Hayya refers to the fifteenth of Shvat as "the day that, in Arabic, is called ‘the second ember,' on which fruit trees begin to absorb water and flourish." And what are "embers"? These, according to the Israeli botanist and naturalist Nogah Hareuveni, are clusters of black, furry caterpillars that appear on wild vegetation and young wheat during the months of January and February. Basing himself on accounts by Arab villagers in the Galilee, Hareuveni reports that such clusters appear in each of three consecutive monthly warming trends, of which the second falls during Shvat.
In citing the "second ember," Hayya Gaon was also harking back to the abovementioned talmudic debate between the followers of Hillel and Shammai. The former identified Shvat 15 as the point at which the earth had warmed up enough to release water into the trees, so that the fruiting process, from here on in, would belong to the following year. The latter, reasoning that the previous month's warming trend had already been adequate to the task, stipulated Shvat 1. The former view prevailed.
As for the speculative reason behind the choice of the fifteenth of Shvat, it rests upon the correspondence of that date with one that falls exactly six months later: the fifteenth of Av. The latter date, says the Talmud in the name of Rabbi Eliezer the Great, is the point after which "the strength of the sun wanes and trees were no longer cut down for the altar because they were no longer dry" (Taanit 31a). If the middle of Av marks the end of summer, then it is not unreasonable to assume that the middle of Shvat, a half-year earlier, marks the end of winter.
The final puzzle remains: how did Tu Bishvat become "Arbor Day"?
In medieval Germany, it appears, a custom began of eating fruit on this day. By the 16th century, it had spread to Eastern Europe and then to Western Europe and North Africa. Evidently, it was intended to strengthen a longing for the days in which Israel dwelled securely in its home and could easily observe the commandments of tithing.
At about the same time, the kabbalists of Safed, whose affinity with nature led them to go out into the fields to pray, began to mark the occasion with a festive meal paralleling the Passover seder. One of its key features was the drinking of four glasses of wine, transitioning from white to red—a custom likely inspired by the physical changes undergone by the land's fruit trees during this season.
The rest of the story is linked closely to the history of modern Zionism. Most fruit trees are deciduous, and are usually planted while still leafless—meaning, well before Tu Bishvat. But, in Hareuveni's estimation, the early pioneers from Russia, motivated to renew ancient agricultural traditions, remembered from home the custom of eating fruit on Tu Bishvat and made a natural association with the "new year of trees." When the Jewish National Fund, founded in 1901, began soliciting money for the explicit purpose of planting trees, the practice of celebrating Tu Bishvat as Arbor Day was soon institutionalized.
Out of this practice there emerged the pleasing paradox of "a festival of the Land of Israel developed in the Diaspora"—and, in time, the planting of over 240 million trees.
Moshe Sokolow is professor of Jewish education at the Azrieli Graduate School of Yeshiva University.
You can find this online at: http://www.jidaily.com/tu