Trees were the tallest of the olvar of Yavanna, plentiful throughout Middle-earth and formed forests. Although the trees were olver, some trees were animate, like the Huorns. There was also the race known as Ents, herders of the trees.
- "During the first year of the boy’s [Tolkien’s] life Arthur Tolkien made a small grove of cypresses, firs, and cedars. Perhaps this had something to do with the deep love of trees that would develop in Ronald."
- ― J.R.R. Tolkien: A Biography
Trees were of special importance to Tolkien - in his short story "Leaf by Niggle", which in a sense was an elaborate allegory explaining his own creative process, the protagonist, Niggle, spends his life painting a single Tree.