Christmas bells vs flower

Christmas bells and flower both are nouns.

Word	Noun	Adjective	Verb	Adverb
Christmas bells	Yes	No	No	No
flower	Yes	No	Yes	No

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

Christmas bells: any of several plants of the genus Blandfordia having large orange or crimson flowers
flower: a plant cultivated for its blooms or blossoms

Christmas bells (noun)	flower (noun)
any of several plants of the genus Blandfordia having large orange or crimson flowers	a plant cultivated for its blooms or blossoms
	reproductive organ of angiosperm plants especially one having showy or colorful parts
	the period of greatest prosperity or productivity

Christmas bells (verb)	flower (verb)
	produce or yield flowers