shrubby penstemon vs wildflower

shrubby penstemon and wildflower both are nouns.

Word	Noun	Adjective	Verb	Adverb
shrubby penstemon	Yes	No	No	No
wildflower	Yes	No	No	No

As nouns, wildflower is a hypernym of shrubby penstemon; that is, wildflower is a word with a broader meaning than shrubby penstemon:

shrubby penstemon: low bushy plant with large showy pale lavender or blue-violet flowers in narrow clusters at ends of stems
wildflower: wild or uncultivated flowering plant

Other hypernyms of shrubby penstemon include wild flower.

shrubby penstemon (noun)	wildflower (noun)
low bushy plant with large showy pale lavender or blue-violet flowers in narrow clusters at ends of stems	wild or uncultivated flowering plant