The Letters of J.R.R. Tolkien, Letter 165 (1955), quote: “I am (obviously) much in love with plants and above all trees, and always have been; and I find human maltreatment of them as hard to bear as some find ill-treatment of animals.”

Tolkien, taking a walk in Oxford, talking about his special relation to trees

https://youtu.be/w9OG6GpisIQ?t=434

“I have always been (…) enormously attracted by trees. All my works are full of trees. I suppose, I have actually in some simple-minded way (?) of longing – I should have liked to be able make contact with a tree and find out how it feels about things.”

Letter from Tolkien to The Daily Telegraph in 1972:

(ref. http://www.houghtonmifflinbooks.com/features/lordoftheringstrilogy/lessons/six/savage.jsp)

Dear Sir,

With reference to the Daily Telegraph of June 29th, page 18, I feel that it is unfair to use my name as an adjective qualifying ‘gloom’, especially in a context dealing with trees. In all my works I take the part of trees as against all their enemies. Lothlórien is beautiful because there the trees were loved; elsewhere forests are represented as awakening to consciousness of themselves. The Old Forest was hostile to two-legged creatures because of the memory of many injuries.

Fangorn Forest was old and beautiful, but at the time of the story tense with hostility because it was threatened by a machine-loving enemy. Mirkwood had fallen under the domination of a Power that hated all living things but was restored to beauty and became Greenwood the Great before the end of the story.

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It would be unfair to compare the Forestry Commission with Sauron because as you observe it is capable of repentence; but nothing it has done that is stupid compares with the destruction, torture and murder of trees perpetuated by private individuals amd minor official bodies. The savage sound of the electric saw is never silent wherever trees are still found growing.

Yours faithfully,

J.R.R. Tolkien
(from The Letters of J.R.R. Tolkien, edited by Humphrey Carpenter, Houghton Mifflin, 1981, pages 419-420)