What happened to the Entwives?

Answer 1

The Ents were interested in nurturing growing things far and wide in the wild, so they travelled widely. The Entwives (the female of the species) preferred to take care of orchards and plants that lived in ordered and cultivated rows. So they parted ways a very long time before the adventures in the Lord of the Rings.

When the Ents came back, the Entwives had gone to cultivate other areas, and the Ents couldn't find them, although they never give up the quest.