onion plant vs alliaceous plant

onion plant and alliaceous plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
onion plant	Yes	No	No	No
alliaceous plant	Yes	No	No	No

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

onion plant: bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb
alliaceous plant: bulbous plants having a characteristic pungent onion odor

onion plant (noun)	alliaceous plant (noun)
bulbous plant having hollow leaves cultivated worldwide for its rounded edible bulb	bulbous plants having a characteristic pungent onion odor