Tu Bi'Shvat is one of the happier festivals in the Jewish calendar. It's other name means "New Year for the Trees" and it is essentially about planting new trees. In one of those moments of Judaic insights which resonates down the millenia, the rabbis have left us with a tradition of returning to nature something of what we have taken away. The modern trend has been for communities to collect money to pay for trees in Israel as well as in their own town. In these ecologically aware times, contributing to reforestation programmes in the Amazon and elsewhere has also become common.
Tu Bi'Shvat (the 16th of the month of shvat) is also significant as the beggining of the taxable year.