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