According to the sifrei kabala, reciting the bracha on fruit trees in the month of Nissan, is a big tikkun (spiritual repair) for those neshamos that are hovering between the two worlds as gilgulim (reincarnated souls) in the barks of trees, and it is important when saying this bracha to have in mind to bring heavenly mercy upon these hovering souls to allow them to be freed from their pain by enabling them to return to their place in olam haba (see shu”T teshuvos v’hanhagos vol. 1 end of siman 191 and kaf hachaim 226:8. See kaf hachaim 226:4 that this bracha should not be made on Shabbos, as doing so will be “Borer”, separating the “Sparks of kedusha” of the neshamos from the trees!)
