alkali grass vs zigadene

alkali grass and zigadene both are nouns.

Word	Noun	Adjective	Verb	Adverb
alkali grass	Yes	No	No	No
zigadene	Yes	No	No	No

As nouns, zigadene is a hypernym of alkali grass; that is, zigadene is a word with a broader meaning than alkali grass:

alkali grass: plant of western North America having grasslike leaves and greenish-white flowers
zigadene: any of various plants of the genus Zigadenus having glaucous leaves and terminal racemes of mostly white flowers; all are poisonous

Other hypernyms of alkali grass include death camas.

alkali grass (noun)	zigadene (noun)
plant of western North America having grasslike leaves and greenish-white flowers	any of various plants of the genus Zigadenus having glaucous leaves and terminal racemes of mostly white flowers; all are poisonous