grassy death camas vs zigadene

grassy death camas and zigadene both are nouns.

Word	Noun	Adjective	Verb	Adverb
grassy death camas	Yes	No	No	No
zigadene	Yes	No	No	No

As nouns, zigadene is a hypernym of grassy death camas; that is, zigadene is a word with a broader meaning than grassy death camas:

grassy death camas: plant of western North America to Mexico; poisonous especially to grazing animals
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 grassy death camas include death camas.

grassy death camas (noun)	zigadene (noun)
plant of western North America to Mexico; poisonous especially to grazing animals	any of various plants of the genus Zigadenus having glaucous leaves and terminal racemes of mostly white flowers; all are poisonous