Owning a fruit tree was a form of wealth in Biblical Old Testament times and, in an age where the religion and government were one body, it's safe to say that there was a tax or tithe to pay:
When you come to the land and you plant any tree, you shall treat its fruit as forbidden; for three years it will be forbidden and not eaten. In the fourth year, all of its fruit shall be sanctified to praise the L-rd. In the fifth year, you may eat the fruit.
Just like there are many modern years, such as calendar years, school years and fiscal years, it was necessary to create a standard for determining years for a tree for tax/tithe purposes. Tu B'Shevat, today, is the is the day when all trees age one year from Tu B'Shevat last year, regardless of the calendar date when they were physically planted in between. This day remains on the Jewish calendar because it's a tradition although not all that many Jews grow fruit trees in the 21st century. However, green-thinking Jews have evolved the holiday through time, making it a Jewish Earth Day!
During the 17th century, the Kabbalists were inspired by Deuteronomy 20:19, "For man is like the tree of the field." A ritual for Tu B'Shevat was created that included a special order service called a seder. The idea was to repeat this ritual annually to contemplate the relationship between humanity and trees. In order to be consistent, there is a written text, called a haggadah, that was followed during the service.
CLICK HERE FOR ONE VERSION OF THE MODERN TU B'SHEVAT HAGGADAH TEXT.
Tu B'Shevat seders always include the idea of planting. Sometimes, parsley seeds are planted as part of the ritual because there is exactly enough time to grow a windowsill pot of parsley to be harvested for use in the ritual of the Passover seder. Others participate in planting trees in Israel to remember the victims of the Holocaust.
Today, and I do mean right now, Jewish green organizations are making commitments to reduce inefficient energy use and wasteful food consumption as reported in news today. What began as a necessary part of the taxation process has completely evolved into the Jewish Earth Day celebration. Yes, and with celebration, there is song and art! In closing, I'll share a fun Tu B'Shevat song for children! It's truly a great day to sing and dance among trees!