In The Future  the Barren Trees will Bear Fruit

“And the trees of the field will bear fruit.” Chazal say that in the future to come, the barren or fruitless trees will bear fruit. In truth, trees were created to bear fruit but as a result of Adam’s sin the earth was also cursed and many species of trees are incapable of bearing fruit. (See Netzach Yisrael, Chapter 50 authored by Rabbi Yehuda Lowe zt’l, the Maharal of Praque.)

On 15 Shevat, the Rosh Hashanah of the trees, the trees are judged if they will merit to bear fruit in the coming summer. The implication is if we will merit the Final Redemption; for then, even the fruitless tress will bear fruit. Undoubtedly, it is a day that all the non-bearing fruit trees pray along with us for the Final Redemption.
This may be the intent of the verse in Tehilim 96:12, “then all the forest trees will sing praises”. This verse is discussing the days of Moshiach when even the Ilanei S’rak will merit to bring forth fruits; and then they will sing praises.

Now on the day of Tu Beshvat when the barren trees are judged if it will be fulfilled in them the verse, “and the tree of the field will give forth its fruit.” There is an amazing Gematria – the numerical value of the letters in this verse equals 1236 - the same numerical value of the letters of the words, “Chamisha Asar BiShvat”, 15 Shevat!
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As it is known that “Man is a tree of the field”. One who feels devoid of mitzvos and Maasim Tovim, like the tree that cannot bear fruit, will find Tu Bishvat an auspicious day to beseech Hashem for special consideration and merit to realize his potential. 

~ Harav Moshe Wolfson in Emunas Itecha – Chodeah Shevat
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Perhaps the implication is that it is an auspicious time for childless couples as well to entreat the Creator to merit children.