hawk's-beard vs wild flower

hawk's-beard and wild flower both are nouns.

Word	Noun	Adjective	Verb	Adverb
hawk's-beard	Yes	No	No	No
wild flower	Yes	No	No	No

As nouns, wild flower is a hypernym of hawk's-beard; that is, wild flower is a word with a broader meaning than hawk's-beard:

hawk's-beard: any of various plants of the genus Crepis having loose heads of yellow flowers on top of a long branched leafy stem; Northern Hemisphere
wild flower: wild or uncultivated flowering plant

Other hypernyms of hawk's-beard include wildflower.

hawk's-beard (noun)	wild flower (noun)
any of various plants of the genus Crepis having loose heads of yellow flowers on top of a long branched leafy stem; Northern Hemisphere	wild or uncultivated flowering plant