whortleberry vs blueberry bush

whortleberry and blueberry bush both are nouns.

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

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

whortleberry: erect European blueberry having solitary flowers and blue-black berries
blueberry bush: any of numerous shrubs of the genus Vaccinium bearing blueberries

Other hypernyms of whortleberry include blueberry.

whortleberry (noun)	blueberry bush (noun)
blue-black berries similar to American blueberries	any of numerous shrubs of the genus Vaccinium bearing blueberries
erect European blueberry having solitary flowers and blue-black berries