TU B'SHEVAT begins tonight at sundown. This is the "new year for trees," i.e., the date on which one reckons a tree to be a year older for the purpose of determining when it has reached its fifth year and its fruit may be eaten, as per Leviticus 19:23-25:

23: "When you come into the land and plant all kinds of trees for food, then you shall count their fruit as forbidden; three years it shall be forbidden to you, it must not be eaten.
24: And in the fourth year all their fruit shall be holy, an offering of praise to the LORD.
25: But in the fifth year you may eat of their fruit, that they may yield more richly for you: I am the LORD your God. (RSV)

In honor of the day, the Jerusalem Post has the following articles:

"A Tu Bishvat compendium"

"Tempted by the 'etrog'"