The origins of Tu b'Shvat
Tu b'Shvat is a New Year for trees. This might seem a strange concept for anyone living outside of the Levitical law but it has a very practical function. There are a number of commandments in the Torah concerning trees. The Israelites were forbidden to eat the fruit of a new tree for three years after it had been planted. On the fourth year the fruit had to be given as a praise offering and only on the fifth year might the fruit be eaten (Leviticus 19:23-25). Since trees produce fruit at different times and have quite a long process leading up to fruit formation, a problem arose in determining in which year the fruit of the tree originated. It was therefore decided that a date should be set to mark a change of year for trees. In Israel the rains come in the winter and are mostly finished by mid-February. Deciduous trees drop their leaves in winter and very little sap is drawn up through the plant. As spring approaches, the sap begins to flow again and new growth starts. The sages decided that the time when the rain stopped and sap began to flow was the point when the New Year began for trees. There was some discussion as to the exact date but it was eventually set at 15 Shvat, which usually occurs in February. If you were in the fourth year after planting a new tree and looking to the fifth, any fruit that started to form before 15 Shvat was holy and should be offered to God, but any starting to form after that date was your own and could be eaten. It was also important for tithing. A tenth of each year's produce had to be given to the priests. Tu b'Shvat provided the date when the next year's crop began. If your tree blossomed before then, even though the fruit had not formed, it counted in last year's tithe.
How Tu b'Shvat developed
Tu b'Shvat is first mentioned in the second century AD in the Mishnah but all the traditions for this festival are late, mostly coming from the Middle Ages onward. In Eastern Europe it became a custom to eat 15 different kinds of fruit and to try if possible to have some dried ones from Israel. This was often carob as they survived well on the long journey. Almonds were seen as especially linked to this festival as they are the first tree to blossom in Israel and this frequently coincided with Tu b'Shvat. Psalm 104 was recited, which emphasises God as creator.
In the sixteenth century in Israel, the kabbalistic Jews of Safed developed an elaborate service called a Tu b'Shvat Seder. Modelled on a Passover meal, it had its own special traditions. They noticed that different colour flowers predominated during different seasons in the Holy Land and wove these colours into their celebration of the changing seasons.
A theme in many modern Tu b'Shvat celebrations is the Sabbatical year commanded in Leviticus 25. The Israelites were commanded to give the land a rest every seventh year. They were allowed to eat anything that grew naturally, but not to plough, plant or systematically harvest crops. In this way the land could regenerate itself and produce more abundantly in the other six years. Apart from being a good early example of using fallow years in agriculture, the purpose of the sabbatical year was to teach the Israelites that they did not own the land. This was holy and belonged to God, who lent it to them. Consequently they should treat it with respect. When the people of God were carried off into exile for disobedience, this was mentioned. Farmers had not been abiding by the Sabbatical year rule and so God had intervened: `The land enjoyed its Sabbath rests, all the time of its desolation it rested, until the seventy years [of exile] were completed' (2 Chronicles 36:21).
From Tu b'Shvat we can learn that as we have benefited from previous generations in, for example, the planting of fruit trees. We in turn should provide for those coming after us. There is a lovely verse in Deuteronomy that sums up this respectful attitude:
When you lay siege to a city for a long time, fighting against it to capture it, do not destroy its trees by putting an axe to them, because you can eat their fruit. Do not cut them down. Are the trees of the field people, that you should besiege them? (Deuteronomy 20:19)