There are those who claim the custom to celebrate Tu-beshevat as a holiday is based upon the book Hemdat Yamim. This book, according to many, was either written by Nathan of Gaza (Shabbati Zvi's "prophet") or one of follower of Shabbati Zvi. (This is contrary to the assertion in the Philogos that Nathan is not author, a contention which has little to no source). In Ha'aretz, an article appeared with this contention, namely the source for the Tu-beshevat custom is Sabbatian or as the headline reads "The New Year for the Trees, Isn't is Shabbati Zvi."
However, a closer look at the history reveals, that although some of the customs on Tu-beshevat can be traced to Hemdat Yamim the actual celebration dates much earlier. Avraham Ya'ari, the noted bibliographer, in an article traced the history of Tu-beshevat. He explains that much of the early mentions of Tu-beshevat were only in the negative, i.e. one can't fast or say tachanun. Obviously, the first mention is in the Mishna in Rosh Hashana which states, according to Bet Hillel, Tu-beshevat is the new year for trees. The new year does not conotate a New Years like celebration, instead, this only has implications for questions of tithing. One can't tithe fruits from one year using a different years fruits. Thus the 15th of Shevat is the cut off point.
Ya'ari, however, notes the first mention in connection to a celbration or the like is in the 16th century. Specifically, R. Issachar ibn Susan (c. 1510-1580) in Ibur Shanim, published in 1578 (the book was published earlier, in 1564, this was done without the knowledge or R. Issachar and according to R. Issachar, with numerous errors) he mentions "the Ashkenazim have the custom [on Tu-beshevat] to eat many fruits in honor of the day." Mention of this custom also appeared in a Jedeo-German Minhagim book first published in 1590. "The custom is to eat many fruits as it is the New Year of the trees."
In the community of Worms there was a rather interesting permentation of the custom. As R. Jousep Schammes in his Minhagim de Kehilah Kedosha Vermaysa, states:
However, a closer look at the history reveals, that although some of the customs on Tu-beshevat can be traced to Hemdat Yamim the actual celebration dates much earlier. Avraham Ya'ari, the noted bibliographer, in an article traced the history of Tu-beshevat. He explains that much of the early mentions of Tu-beshevat were only in the negative, i.e. one can't fast or say tachanun. Obviously, the first mention is in the Mishna in Rosh Hashana which states, according to Bet Hillel, Tu-beshevat is the new year for trees. The new year does not conotate a New Years like celebration, instead, this only has implications for questions of tithing. One can't tithe fruits from one year using a different years fruits. Thus the 15th of Shevat is the cut off point.
Ya'ari, however, notes the first mention in connection to a celbration or the like is in the 16th century. Specifically, R. Issachar ibn Susan (c. 1510-1580) in Ibur Shanim, published in 1578 (the book was published earlier, in 1564, this was done without the knowledge or R. Issachar and according to R. Issachar, with numerous errors) he mentions "the Ashkenazim have the custom [on Tu-beshevat] to eat many fruits in honor of the day." Mention of this custom also appeared in a Jedeo-German Minhagim book first published in 1590. "The custom is to eat many fruits as it is the New Year of the trees."
In the community of Worms there was a rather interesting permentation of the custom. As R. Jousep Schammes in his Minhagim de Kehilah Kedosha Vermaysa, states:
On Purim and the 15 of Av and Shevat these were vacation days for the Rabbis, especially the 15ht and the 33rd day of the Omer for the students and their teachers. On these days the students did not go to school nor did the teachers go in. The teachers were required to distribute to the students as they left that morning, on the 15th and the 33rd day of the Omer whiskey and sweet cake from the teachers' own pocket, they should not charge the students, this is the custom.
He repeats this in his comments to the 15th of Shevat. "One doesn't say tehina even during the morning prayer. It is a vacation day for the students and the teachers, especailly the younger students, it is a holiday for the teachers. The custom is for the teachers to distribute whiskey to the students and make merry with them."
While we have shown there was a custom for those Ashkenazim to celebrate Tu-beshevat, amongst the Sefardim, it is correct the source is Hemdat Yamim. Hemdat Yamim, first published in 1732 anonymously has the entire seder for Tu-beshevat. This includes passages from the Bible as well as specific foods. This in turn was popularized to a greater degree when it was included in the book Pri Etz Hadar first published in 1753 and republished an additional 29 times by 1959. This book included the entire Hemdat Yamim service.
So at the end of the day, although some of the customs of Tu-beshvat may come from the Hemdat Yamim he clearly is not the only or the first source for celebrating Tu-beshevat.
For more on the Hemdat Yamim, a controversy that has recently been stirred up again with the republication by R. Moshe Tzuriel of the Hemdat Yamim with an extensive introduction. Additionally, Ya'ari has a book Talmuot Sefer which his conclusion has been disproven by Tishbi in his Nitvi Emunah U'Minut. R. Tzuriel's publication engendered the publication of a small pamphelet Hemdat Yosef as well as a bunch of articles in the journal Hechal HaBeshet. Rabbi Dr. Leiman in his latest article in Ohr haMizrach has a footnote with all the citations. [R. Dr. Leiman's article collects all of R. Y. Eybeschit's and R. Y. Emden's approbations].
Also, anyone can get a copy of Hemdat Yamim. There are two places on the web where it is available free. The first is at the Jewish National Libraries site for rare books online here. For this one you need to download their viewer. Or at SeforimOnline.org (which for some reason is not online as I write this). Who has it in PDF format?
Additionally, Ya'ari has an article on the piyutim for Tu-beshevat here.
While we have shown there was a custom for those Ashkenazim to celebrate Tu-beshevat, amongst the Sefardim, it is correct the source is Hemdat Yamim. Hemdat Yamim, first published in 1732 anonymously has the entire seder for Tu-beshevat. This includes passages from the Bible as well as specific foods. This in turn was popularized to a greater degree when it was included in the book Pri Etz Hadar first published in 1753 and republished an additional 29 times by 1959. This book included the entire Hemdat Yamim service.
So at the end of the day, although some of the customs of Tu-beshvat may come from the Hemdat Yamim he clearly is not the only or the first source for celebrating Tu-beshevat.
For more on the Hemdat Yamim, a controversy that has recently been stirred up again with the republication by R. Moshe Tzuriel of the Hemdat Yamim with an extensive introduction. Additionally, Ya'ari has a book Talmuot Sefer which his conclusion has been disproven by Tishbi in his Nitvi Emunah U'Minut. R. Tzuriel's publication engendered the publication of a small pamphelet Hemdat Yosef as well as a bunch of articles in the journal Hechal HaBeshet. Rabbi Dr. Leiman in his latest article in Ohr haMizrach has a footnote with all the citations. [R. Dr. Leiman's article collects all of R. Y. Eybeschit's and R. Y. Emden's approbations].
Also, anyone can get a copy of Hemdat Yamim. There are two places on the web where it is available free. The first is at the Jewish National Libraries site for rare books online here. For this one you need to download their viewer. Or at SeforimOnline.org (which for some reason is not online as I write this). Who has it in PDF format?
Additionally, Ya'ari has an article on the piyutim for Tu-beshevat here.