Well...I'm still fairly sure I read that, but I haven't had a chance to do a good search. I found this at
the Grey Havens, it's from
Letters:
"What happened to them is not resolved in this book. ... I think that in fact the
Entwives had disappeared for good, being destroyed with their gardens in the
War of the Last Alliance (
Second Age 3429-3441) when
Sauron pursued a scorched earth policy and burned their land against the advance of the Allies down the
Anduin. They survived only in the 'agriculture' transmitted to
Men (and
Hobbits). Some, of course, may have fled east, or even have become enslaved: tyrants even in such
tales must have an economic and agricultural background to their soldiers and metal-workers. If any survived so, they would indeed be far estranged from the
Ents, and any rapprochement would be difficult - unless experience of industrialised and militarised agriculture had made them a little more anarchic. I hope so. I don't know."
[The Letters of J.R.R. Tolkien, 179 (#144)]
This was actually from before LotR was published, so perhaps
Tolkien figured out a more specific answer later, or maybe what I read in the Sil was Chistopher taking the story a little farther. I don't know, but I'll keep looking for that passage from
the Silmarillion. In the meanwhileI think I'll take back all that "explicitly stated" crap.
