Tu B'Shevat
Tu B'Shevat: 'The New Year for Trees'?!
Tu B'Shevat is one of the few holidays that comes solely from the Pharisaic Oral Torah [1].
'Shevat' is the name of the eleventh month of the Hebrew calendar and 'Tu B'Shevat' literally means the 15th of Shevat [2].
In Leviticus, the Torah states we cannot eat the fruit of trees planted in Israel for four years but we're allowed to eat them after the fifth year and onwards.
Leviticus 19:23
"And when you have come into the land and planted all kinds of trees for food ... you shall count as uncircumcised (forbidden) their fruit; [for] three years it shall be to you as uncircumcised [and] shall not be eaten".
Leviticus 19:24-5
"But in the fourth year shall all its fruit be holy, a praise to Y-hova [3] and in the fifth year you may eat its fruit that it may yield to you its increase. I [am] Y-hova your G-d".
How Do We Count Tree Years Accurately?
As stated by My Jewish Learning,
"This law ... raised the question of how farmers were to mark the 'birthday' of a tree. The Rabbis therefore established the 15th of the month of Shevat as a general 'birthday' for all trees, regardless of when they were actually planted" [4].
The Pharisaic tradition therefore effectively established a practice whereby the actual number of years a tree was planted would be replaced by a fictional number of years instead.
The Problem With the Pharisaic Method
Unfortunately, while the Pharisaic amendment can make it 'easier' to determine the number of years a tree has been planted (which may be difficult where lots of trees have been planted or indeed, they plant themselves through natural pollination), this effectively erases two Divine Torah provisions (both the provision to not eat the fruit for three years and also to regard it as holy in the fourth year).
Moreover, not only did the 15th of Shevat prevent the due counting of tree years, it later came to be regarded as a religious holiday in its own right, with traditions and customs unrelated to the counting of tree years.
As stated by Reform Judaism,
"After the destruction of the Second Temple in 70 C.E. and the exile that followed, many ... Jews felt a need to bind themselves symbolically to their former homeland. Tu BiShvat served in part to fill that spiritual need. Jews used this time each year to eat a variety of fruits and nuts that could be obtained from Israel ... The 16th- and 17th-century kabbalists (mystics) of Israel elaborated on those customs, creating a ritual for Tu BiShvat somewhat similar to the Passover seder. On erev Tu BiShvat, they would gather in their homes for a 15-course meal, each course being one of the foods associated with the land ... Today, Tu BiShvat has become more of an environmental holiday: a day to remind us of the Jewish duty to care for the natural world, and a tree-planting festival" [5].
Conclusion
How did we get from counting five years from the date a tree was planted to a 15 course dinner?! If the Torah says we need to count 5 years from the date a tree is planted, we need to find a way to do just that!
References
[1] Mishna (Oral Torah), 'Rosh Hashana 1:1': https://www.sefaria.org/Mishnah_Rosh_Hashanah.1.1?lang=bi&with=Sheets&lang2=bi. "The first mention of the significance of the 15th of Shevat can be found in the Mishnah (Oral Torah), which states ... there are four days ... considered the 'new year', each for a different purpose: 1: The first of Nisan is the new year for kings and festivals. 2: The first of Elul is the new year for the tithe of cattle. 3: The first of Tishrei is the new year for counting years .... calculating Sabbatical years and Jubilee years [and] for planting and for tithing vegetables. 4: The first of Shevat is the new year for trees according to the school of Shammai; the school of Hillel, however, places this on the 15th of Shevat. The halachah follows the school of Hillel", See Chabad, 'Who "Invented" the Holiday on 15 Shevat?': https://www.chabad.org/library/article_cdo/aid/5009491/jewish/Who-Invented-the-Holiday-on-15-Shevat.htm#utm_medium=email&utm_source=1_chabad.org_magazine_en&utm_campaign=en&utm_content=content. Interestingly, out of these four Rabbinical 'new years', it is only the 15th Shevat that is now celebrated as an official Jewish holiday.
[2] 'Tu' stands for the Hebrew letters 'Tet'
and' Vav', which together have the numerical value of 9 and 6, adding up to 15, see Orthodox Union, 'Tu
B'Shevat: New Year for the Trees': https://www.ou.org/holidays/tu_bshevat/.
[3] For more on why I write the name of G-d as I do, see: G-d's Name.
[4] My Jewish Learning, 'Tu Bishvat 101 The "birthday of the trees" is a time for seders, tree-planting and more': https://www.myjewishlearning.com/article/tu-bishvat-ideas-beliefs/.
[5] Reform Judaism, 'Tu BiShvat: Customs and Rituals': https://reformjudaism.org/tu-bishvat-customs-and-rituals.