pepper root vs bittercress

pepper root and bittercress both are nouns.

Word	Noun	Adjective	Verb	Adverb
pepper root	Yes	No	No	No
bittercress	Yes	No	No	No

As nouns, bittercress is a hypernym of pepper root; that is, bittercress is a word with a broader meaning than pepper root:

pepper root: North American herb with pungent scaly or toothed roots
bittercress: any of various herbs of the genus Cardamine, having usually pinnate leaves and racemes of white, pink or purple flowers; cosmopolitan except Antarctic

Other hypernyms of pepper root include bitter cress.

pepper root (noun)	bittercress (noun)
North American herb with pungent scaly or toothed roots	any of various herbs of the genus Cardamine, having usually pinnate leaves and racemes of white, pink or purple flowers; cosmopolitan except Antarctic