• 01.083 and hear the pine-trees
• 01.123 and the pine-trees on the Mountain creaking
• 03.012 and the smell of the pine-trees made him drowsy,
• 06.060 out of his pine-tree.

This word is found as a single word, as a hyphenated word, and as a two-word word in OED.  It is only found hyphenated in The Hobbit.

“pine tree, n.” OED Online, Oxford University Press, June 2017, http://www.oed.com/view/Entry/144123. Accessed 19 September 2017.