Q. Why and when is it best to eat the fruits on T’u Bishvat, the night before or during the day? Before the seuda, during, or after the seuda? Should one encourage making a seuda for chinuch of children?
A. The tradition to eat fruits on Tu Bishvat is not very ancient. It is first mentioned on Tikun Isoschor, and it goes back only to the times of the Bais Yosef. Mogen Arohom (131: 16) does mention it.
It is strongly upheld by the Sephardi communities, and followers of the traditions of the Arizal. who observe it as a very saintly and special day and consider the minhogim as a great and important avoda or holy labor.
Followers of the Arizal also eat a minimum of 12 to 15 fruits (Maharam Hagiz). Some maintain that 30 different fruits should be consumed. (Even Yisroel p. 28). Others opine that one should try all fruits available at that location. (Mekor Chaim 684).
Bnei Yissochor writes that our sources refer to Tu B’Shevat as the "New Year of the Tree", (Mishna Rosh Hashana 2a) in the singular. This implies that while Tu Bishvat is the New Year of all trees, we are to concentrate on one tree in particular, the one that provides the esrog for Sukos. There is a tradition, to pray on this day to have the privilege of acquiring a beautiful esrog. There is also a minhag to preserve the esrog in jam or to create a liquor from it, and to eat it or drink it on Tu Bishvat. Chasidim and Kabbalists also prepare a seuda, a “tish” or a sort of "Seder Night" on Tu Bishvat, over four cups of wine, light candles and have a seder plate with different types of fruits. (See question 453 in regards to fruits from Eretz Yisroel, see also Nitei Gavriel 4: 2; n. 4).
On question 1256 in regards to when to to eat the fruits, we wrote; Poskim mention to eat them at the end of the seuda (Ohr Zarua 2: 21, Darchei Moshe O.H. 149: 4, Magen Avrohom, Biur Halacha ibid. Nitei Gavriel – Purim 9: 2) so they are included in Birchas Hamazon (Tosafos Brochos 41b) and when it is Shabbos to avoid spoiling the appetite for the Shabbos meal.
When in Shabbos, Horav Shlomo Miller’s Shlit’a opinion is that if one has young children and is concerned that they will not be awake at the end of the seuda, he may eat them after hamotzi.
Horav Shlomo Miller’s Shlit’a opinion is that one should maintain the minhogim and traditions of his family or the community he belongs.
Rabbi Abraham Bartfeld as revised by Horav Shlomo Miller Shlit’a