huckleberry vs blueberry bush

huckleberry and blueberry bush both are nouns.

Word	Noun	Adjective	Verb	Adverb
huckleberry	Yes	No	No	No
blueberry bush	Yes	No	No	No

As nouns, blueberry bush is a hypernym of huckleberry; that is, blueberry bush is a word with a broader meaning than huckleberry:

huckleberry: any of various dark-fruited as distinguished from blue-fruited blueberries
blueberry bush: any of numerous shrubs of the genus Vaccinium bearing blueberries

Other hypernyms of huckleberry include blueberry.

huckleberry (noun)	blueberry bush (noun)
blue-black berry similar to blueberries and bilberries of the eastern United States	any of numerous shrubs of the genus Vaccinium bearing blueberries
any of several shrubs of the genus Gaylussacia bearing small berries resembling blueberries
any of various dark-fruited as distinguished from blue-fruited blueberries