Nice piece of work, very extended. But…

The poem Treebeard sings (Oh Rowan mine, I saw you shine…) which he mentioned as his work, is neither his nor Elvish, but it is a piece of Bregalad. Bregalad is a young Ent, in the term of the Ents a hasty one. So when Entmoot continues, Bregalad takes the Hobbits to his home. During the walk, he tells them about the entwives and he gives them the poem. So it is a nice tribute to Bregalad.

The last line of the poem, heard in the movie (Come to me…) is the Elvish poem.