This year the New Year of the Trees, Tu Bishvat (ט"וּ בִּשְׁבָט), is a celebration of the blossoming of trees. The fruit of a tree may not be used during the first three years (marked by this date). In the fourth year the fruit may be used for sacrifices (tithed), but it may not be eaten until the fifth year. (This is found in Leviticus 19:23 et seq.) In ancient times, when “taxes” (tithes) were assessed, trees that blossomed after 15 Shevat were considered a part of the farmer’s income for the following year once they were four years old.
To celebrate Tu Bishvat, we eat a tree fruit that we haven’t yet eaten this season, and say - of course - the blessing over the fruit of the tree, בּוֹרֵא פְּרִי הָעֵץ, along with the Sheheheyanu.