TOLKIEN HAD THE WORDS FOR IT 19: THE TREASON OF ISENGARD

'I do not know what fables men have made out of old knowledge,' said Aragorn. 'And of the truth little is now known, even to Keleborn. But I have heard tell that in Fangorn, clinging here on the east side of the last slopes of the Misty Mountains, the ancient trees have taken refuge that once marched dark and proud over the wide lands, before even the first Elves awoke in the World. Between the Baranduin and the Barrowdowns is another forest of old trees; but it is not as great as Fangorn. Some say that both are but the last strongholds of one mighty wood, more vast than Mirkwood the Great, that held under its dominion all the countries through which now flow the Greyflood and the Baranduin; others say that Fangorn is not akin to the Old Forest, and that its secret is of other kind.'

The Treason of Isengard