Tu Bishvat is sometimes referred to as the day in which the sap begins to rise in the trees. From where does this teaching arise? “A Tree Comes of Age” by Rabbi Dr. Sperber was originally given as a lecture on Parashat Yitro 5769/ February 14, 2009 and published on Bar-Ilan University’s Parashat Hashavua Study Center’s website, here. We have formatted the essay adding a number of the sourcetexts referred to in the lecture and all referenced citations.