alyssum vs cruciferous plant

alyssum and cruciferous plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
alyssum	Yes	No	No	No
cruciferous plant	Yes	No	No	No

As nouns, cruciferous plant is a hypernym of alyssum; that is, cruciferous plant is a word with a broader meaning than alyssum:

alyssum: any garden plant of the genus Alyssum having clusters of small yellow or white flowers
cruciferous plant: any of various plants of the family Cruciferae

Other hypernyms of alyssum include crucifer.

alyssum (noun)	cruciferous plant (noun)
any garden plant of the genus Alyssum having clusters of small yellow or white flowers	any of various plants of the family Cruciferae