peach bells vs bellflower

peach bells and bellflower both are nouns.

Word	Noun	Adjective	Verb	Adverb
peach bells	Yes	No	No	No
bellflower	Yes	No	No	No

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

peach bells: perennial European bellflower with racemose white or blue flowers
bellflower: any of various plants of the genus Campanula having blue or white bell-shaped flowers

Other hypernyms of peach bells include campanula.

peach bells (noun)	bellflower (noun)
perennial European bellflower with racemose white or blue flowers	any of various plants of the genus Campanula having blue or white bell-shaped flowers