hawk's-beard vs wildflower

hawk's-beard and wildflower both are nouns.

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

As nouns, wildflower is a hypernym of hawk's-beard; that is, wildflower 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
wildflower: wild or uncultivated flowering plant

Other hypernyms of hawk's-beard include wild flower.

hawk's-beard (noun)	wildflower (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