Tu B'shevat Jewish New Year for TreesTu B'Shevat is the new year for the purpose of calculating the age of trees for tithing. See Lev. 19:23-25, which states that fruit from trees may not be eaten during the first three years. The fourth year's fruit is for G-d, and after that, you can eat the fruit. Each tree is considered to have aged one year as of Tu B'Shevat.
Tu B'Shevat is not mentioned in the Torah.
To celebrate The New Year for Trees, here are a few of my designs: