blueberry vs blueberry bush

blueberry and blueberry bush both are nouns.

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

As nouns, blueberry and blueberry bush are synonyms defined as:

blueberry and blueberry bush: any of numerous shrubs of the genus Vaccinium bearing blueberries

blueberry (noun)	blueberry bush (noun)
sweet edible dark-blue berries of either low-growing or high-growing blueberry plants	any of numerous shrubs of the genus Vaccinium bearing blueberries
any of numerous shrubs of the genus Vaccinium bearing blueberries