The Tu B’shvat is the New Year for the Trees. One tradition for Tu B’shvat is having a seder, a flexible ritual with no set liturgy. The seder usually includes some common elements such as four cups of wine and four kinds of symbolic fruits. A seder for Tu Bishvat can focus on ecology, or Israel, or any of a number of other themes.
Throughout history, Jews throughout the world have maintained connections with the Land of Israel on Tu B’shvat by eating fruits produced there.
For the kabbalists [mystics], this symbolic gesture has tremendous spiritual ramifications. According to their explanation, every piece of fruit–which can be considered the parent generation–holds the seed of the next generation, in other words, the potential for new life. If, when we eat the fruit, which releases the seed, we do so in a holy way–with proper blessing and gratitude–then we are helping God to renew nature, and the flow of life continues.
Source: myjewishlearning.com