western larch vs Oregon larch

western larch and Oregon larch both are nouns.

Word	Noun	Adjective	Verb	Adverb
western larch	Yes	No	No	No
Oregon larch	Yes	No	No	No

As nouns, western larch and Oregon larch are synonyms defined as:

western larch and Oregon larch: tall larch of western North America have pale green sharply pointed leaves and oblong cones; an important timber tree

Other synonyms of western larch include Larix occidentalis, western tamarack.

western larch (noun)	Oregon larch (noun)
tall larch of western North America have pale green sharply pointed leaves and oblong cones; an important timber tree	tall larch of western North America have pale green sharply pointed leaves and oblong cones; an important timber tree