There is a wonderful rabbinic legend that says that God transported Moses to a session of the academy in which Rabbi Akiva was teaching. Moses stood at the rear and listened to the discussion and could not understand a word of it. He was very perturbed, but then he heard Akiva explain a certain law with the statement, "This is the law according to Moses from Sinai" and was content (Menahot 29b). This unusual story was intended to convey two messages: that through the centuries there was change and development of Halacha and that the development of Jewish practice was such that it all could be traced back to the beginning, to Moses at Sinai, even though Moses himself would not have recognized it. Like a plant or a tree it all springs from the roots and develops organically. Which brings me to Tu Bishvat, which we will be celebrating in another 10 days. It is a perfect example of these two truths. If Moses were to return this week - or even if Rabbi Akiva were to make a sudden appearance - and see how Tu Bishvat is celebrated, be it with tree planting or with a special Seder or even just the serving of fruits native to Israel - neither Moses nor Akiva would have any idea what was going on or why. At the time of Moses no one had ever heard of Tu Bishvat - as a matter of fact no one had ever heard of the month of Shvat, that name originated much later during the Babylonian exile (See Zechariah 1:7). At the time of Akiva, they would have known of Tu Bishvat simply as a date on the Hebrew calendar which was a cutoff date for tithing. As the Mishna records it: There are four beginnings of the year (new years)... on the first of Shvat is the beginning of year for trees according to the School of Shammai; the School of Hillel says - the 15th thereof (Rosh Hashana 1:1). As the rabbis explained, "If the fruit of a tree blossoms before the 15th of Shvat, it is tithed for the outgoing year; if after the 15th of Shvat, it is tithed for the incoming year" (Rosh Hashana 15b). At a much later time Jewish communities in Europe adopted the practice of eating fruits - especially fruits connected with the Land of Israel - on that date and reciting special psalms that were appropriate. It is easy to understand why they did that. Tithing had no practical meaning for them since it was practiced only in the Land of Israel. By eating fruits of Israel on that day they were able to strengthen their ties with the land and to give some importance to a date that would otherwise be meaningless. In the 16th century, kabbalists added to this practice by instituting a Seder Tu Bishvat patterned after the Seder of Pessah, a liturgy which gave a framework for eating 15 fruits (since the holiday is on the 15th of the month) and drinking four cups of wine. The various fruits were also accorded symbolic and mystical meaning. Eating various fruits was said to "repair" the sin of eating the forbidden fruit in Eden. The next step in the organic development of the holiday occurred with the resettlement of the Land of Israel in the 19th century, when the idea of planting trees on that day to accomplish the reforestation of the land was initiated. And so it is today that Tu Bishvat is a time of planting, which may or may not make sense agriculturally. The date was selected in Second Temple times not because it was good for planting, but because it was the time of the ripening of fruit. As a matter of fact Prof. Louis Ginzberg (the great expert on rabbinic literature who taught at the Jewish Theological Seminary of America) explained the difference between the views of Hillel and Shammai as having to do with the fact that Shammaites were wealthy and owned land in the more fertile valleys where trees blossomed earlier, whereas the Hillelites were the poorer farmers whose trees did not blossom until the 15th of the month. All of these developments, then, are natural and organic - springing from the fact that the date has to do with trees - therefore it is Hag Ha'ilanot, the holiday of the trees - and with the fruit of the trees. How does all of this connect with Moses and the Torah? The idea for designating a date which is the "new year of the trees" springs from the fact that the Torah of Moses contains commands to give tithes (Leviticus 27:30, Numbers 18:21) and prohibits eating fruit before the fifth year (Lev. 19:23-25). As with many other commands of the Torah, this needs elaboration and explanation to be observed. There must be a cutoff date to know when tithes are to be brought or when the fifth year has arrived. This was determined by the Oral Law, codified later in the Mishna. So indeed it all goes back the Moses and the Torah he taught, which decrees that the fruit of trees must be tithed. This then leads to the decision about Tu Bishvat being the date for counting when trees blossom, which in turn leads to eating fruits on that date and celebrating it, which then leads to planting the trees that yield the fruit. And so we have a day of celebration of nature, a day that naturally connects to ideas of caring for nature, of encouraging ecology so that trees and all green things can grow in this wonderful world that God have given into our care. As the Lord said to Adam and Eve, "Fill the earth and master it" (Genesis 1:28) after which God gave into their care "every seed-bearing plant that is upon all the earth, and every tree that has seed-bearing fruit" (Gen. 1:29) and placed them in the Garden of Eden "to till it and tend it" (Gen. 2:15). And that, as Tu Bishvat reminds us, is still our task. The writer is the head of the Rabbinical Court of the Masorti Movement and the author of several books, the most recent being Entering Torah.