hellebore vs poisonous plant

hellebore and poisonous plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
hellebore	Yes	No	No	No
poisonous plant	Yes	No	No	No

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

hellebore: any plant of the Eurasian genus Helleborus
poisonous plant: a plant that when touched or ingested in sufficient quantity can be harmful or fatal to an organism

hellebore (noun)	poisonous plant (noun)
any plant of the Eurasian genus Helleborus	a plant that when touched or ingested in sufficient quantity can be harmful or fatal to an organism
perennial herbs of the lily family having thick toxic rhizomes