RABBI EPHRAIM MIRETZKY
While the holiday of Tu B’Shevat is known simply as a date on the Hebrew calendar, the Mishnah in Rosh Hashana presents a deeper discussion. There is a machlokes between Beis Shamai and Beis Hillel regarding when the Rosh Hashana l’Ilan, the New Year for trees, should occur.
Beis Shamai maintains that it should be the first of Shevat. Beis Hillel, however, holds that it should be the fifteenth of Shevat — the day we celebrate as Tu B’Shevat.
This raises an important question. What is the significance of this day? Furthermore, what lies at the root of this fundamental disagreement?
Koach and Poel: A Core Theme in Shas
The Lubavitcher Rebbe, among others, develops a consistent theme to explain many disputes between Beis Hillel and Beis Shamai throughout Shas. One illuminating example appears in the Gemara in Shabbos 23b, which discusses how to light the Chanukah menorah.
Beis Hillel rules that we begin with one candle on the first night and increase each day until we reach eight. By contrast, Beis Shamai teaches that we begin with eight candles and decrease each night until only one remains.
Although the Gemara provides specific reasons for each view, the Rebbe highlights a deeper distinction: koach and poel.
Koach refers to potential. Poel refers to actualization.
According to Beis Shamai, we focus on the koach. On the first night of Chanukah, there is already the potential for eight nights of miracles. Therefore, we begin with eight lights.
Beis Hillel, however, focuses on poel — what is presently revealed. On the first night, only one miracle has occurred. Therefore, we light one candle. Each subsequent night reflects the number of miracles that have already unfolded.
Applying Koach and Poel to Tu B’Shevat
This same framework helps us understand the Mishnah in Rosh Hashana regarding the Rosh Hashana l’Ilan. The purpose of this day is practical. It establishes the cutoff for calculating maaser on fruits.
If fruit blossomed before Rosh Hashana l’Ilan, it belongs to the previous year. If it blossomed after, it belongs to the new year. This distinction determines how one calculates the total produce and the required maaser.
We rule in accordance with Beis Hillel that Tu B’Shevat falls on the fifteenth of Shevat. But how did each opinion arrive at its respective date?
The Rebbe cites the Gemara in Rosh Hashana 16a, which teaches that on Sukkos — the fifteenth of Tishrei — we are judged specifically regarding water. However, on Rosh Hashana, we are judged on everything. That includes water as well.
So what is the difference?
On Rosh Hashana, the judgment exists in koach — in potential. On Sukkos, the judgment is finalized in poel — in actualization.
Beis Shamai, who emphasizes koach, calculates Rosh Hashana l’Ilan based on the potential judgment of rain on the first of Tishrei. Four months later is the first of Shevat.
Beis Hillel, who emphasizes poel, bases the date on the revealed judgment of rain on Sukkos, the fifteenth of Tishrei. Four months later is the fifteenth of Shevat — Tu B’Shevat.
Tu B’Shevat and Shavuos: Tree and Fruit
The Satmar Rebbe, quoted in Maayan Hamoed, offers a powerful insight that deepens this discussion.
The Gemara in Megillah 31b teaches that Shavuos is the Rosh Hashana for peiros ha’ilan — the fruits of the tree. Tu B’Shevat, by contrast, is the Rosh Hashana for the ilan itself.
Interestingly, the minhagim appear reversed. On Tu B’Shevat, the New Year for trees, we eat fruits. On Shavuos, the New Year for fruits, we decorate shuls with trees.
At first glance, it seems backwards.
On Shavuos, when we are judged regarding fruits, we are reminded to look at their roots. Fruit does not appear in isolation. It emerges from a tree with deep roots and history. It has a mesorah.
Similarly, the Torah we receive on Shavuos did not appear suddenly. It flows from generations of transmission. Therefore, when we celebrate the fruits, we display the trees.
On Tu B’Shevat, however, we stand in the winter. Trees appear barren and frozen. Yet beneath the surface, sap flows quietly. Life is preparing to emerge.
The koach is present, even when unseen.
Therefore, on Tu B’Shevat we eat fruits — the poel — to remind ourselves of the hidden potential within the tree.
Ki Ha’Adam Eitz HaSadeh
The Torah compares a person to a tree of the field. Just as a tree contains unseen potential, so too does every individual.
Tu B’Shevat calls upon us to recognize both dimensions. We must appreciate what is already actualized in our lives. At the same time, we must nurture the koach within ourselves and within others.
This Tu B’Shevat, may we merit to develop our potential fully. May we help our families, friends, and community discover both their koach and their poel. And may we grow, like trees, toward strength, purpose, and lasting impact.
Rabbi Ephraim Miretzky serves as Regional Director for Greater Washington NCSY, leading impactful programs that inspire Jewish youth and foster leadership throughout the Washington, D.C. region. Rabbi Miretzky can be reached at Miretzkye@ncsy.org.
