[The Squatter of Amon Rûdh]

If Ents use pollenation to reproduce, surely they don't need actually to find the Entwives: they could just stand in an area and release pollen into the air, then cross their fingers. I think that the close personal ties between Entish couples like Fangorn and Fimbrethil indicates something more personal than airborne particles, but that's just some hastily applied logic. Tolkien is, of course, silent on the subject.