silver grass vs genus Festuca

silver grass and genus Festuca both are nouns.

Word	Noun	Adjective	Verb	Adverb
silver grass	Yes	No	No	No
genus Festuca	Yes	No	No	No

silver grass (noun)	genus Festuca (noun)
of Australia and New Zealand	a genus of tufted perennial grasses of the family Gramineae