yellow ironweed vs crown-beard

yellow ironweed and crown-beard both are nouns.

Word	Noun	Adjective	Verb	Adverb
yellow ironweed	Yes	No	No	No
crown-beard	Yes	No	No	No

As nouns, crown-beard is a hypernym of yellow ironweed; that is, crown-beard is a word with a broader meaning than yellow ironweed:

yellow ironweed: perennial herb with showy yellow flowers; the eastern United States
crown-beard: any plant of the genus Verbesina having clustered white or yellow flower heads

Other hypernyms of yellow ironweed include crown beard, crownbeard.

yellow ironweed (noun)	crown-beard (noun)
perennial herb with showy yellow flowers; the eastern United States	any plant of the genus Verbesina having clustered white or yellow flower heads