west coast hemlock vs western hemlock

west coast hemlock and western hemlock both are nouns.

Word	Noun	Adjective	Verb	Adverb
west coast hemlock	Yes	No	No	No
western hemlock	Yes	No	No	No

As nouns, west coast hemlock and western hemlock are synonyms defined as:

west coast hemlock and western hemlock: tall evergreen of western North America; commercially important timber tree

Other synonyms of west coast hemlock include Pacific hemlock, Tsuga heterophylla.

west coast hemlock (noun)	western hemlock (noun)
tall evergreen of western North America; commercially important timber tree	tall evergreen of western North America; commercially important timber tree