brown hickory vs hickory tree

brown hickory and hickory tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
brown hickory	Yes	No	No	No
hickory tree	Yes	No	No	No

As nouns, hickory tree is a hypernym of brown hickory; that is, hickory tree is a word with a broader meaning than brown hickory:

Other hypernyms of brown hickory include hickory.

brown hickory (noun)	hickory tree (noun)
an American hickory tree having bitter nuts	American hardwood tree bearing edible nuts