obedient plant vs physostegia

obedient plant and physostegia both are nouns.

Word	Noun	Adjective	Verb	Adverb
obedient plant	Yes	No	No	No
physostegia	Yes	No	No	No

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

obedient plant: North American plant having a spike of two-lipped pink or white flowers
physostegia: any of various plants of the genus Physostegia having sessile linear to oblong leaves and showy white or rose or lavender flowers

obedient plant (noun)	physostegia (noun)
North American plant having a spike of two-lipped pink or white flowers	any of various plants of the genus Physostegia having sessile linear to oblong leaves and showy white or rose or lavender flowers