wild rice vs genus Zizania

wild rice and genus Zizania both are nouns.

Word	Noun	Adjective	Verb	Adverb
wild rice	Yes	No	No	No
genus Zizania	Yes	No	No	No

wild rice (noun)	genus Zizania (noun)
grains of aquatic grass of North America	wild rice
perennial aquatic grass of North America bearing grain used for food