Tu BiShvat (Hebrew for the 15th day of the Hebrew month of Shvat) is the new year of the trees.
Tu BiShvat, called the "New Year of the Trees," falls at a seemingly incongruous time of year.
Tu BiShvat is a minor festival whose provenance dates only to the time of the Second Temple. However, the kabbalists who clustered around the great fifteenth-century mystic Isaac Luria of Safed placed great weight on the holiday, creating new festivities, gatherings at which hymns were sung, fruit (particularly carob) was eaten, and four cups of wine were taken (as in the Passover seder).
Literally, “four species.” The Torah specifies four species to bring together on Sukkot. The four species are: lulav (branches of palm trees), etrog (citron), hadasim (myrtle branches), and aravot (willows) (Leviticus 23:40).