marsh bellflower vs bellflower

marsh bellflower and bellflower both are nouns.

Word	Noun	Adjective	Verb	Adverb
marsh bellflower	Yes	No	No	No
bellflower	Yes	No	No	No

As nouns, bellflower is a hypernym of marsh bellflower; that is, bellflower is a word with a broader meaning than marsh bellflower:

marsh bellflower: bellflower common in marshes of eastern North America having lanceolate linear leaves and small whitish flowers
bellflower: any of various plants of the genus Campanula having blue or white bell-shaped flowers

Other hypernyms of marsh bellflower include campanula.

marsh bellflower (noun)	bellflower (noun)
bellflower common in marshes of eastern North America having lanceolate linear leaves and small whitish flowers	any of various plants of the genus Campanula having blue or white bell-shaped flowers