genus Echium vs plant genus

genus Echium and plant genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
genus Echium	Yes	No	No	No
plant genus	Yes	No	No	No

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

genus Echium: a genus of bristly herbs and shrubs of the family Boraginaceae
plant genus: a genus of plants

genus Echium (noun)	plant genus (noun)
a genus of bristly herbs and shrubs of the family Boraginaceae	a genus of plants