rock penstemon vs wild flower

rock penstemon and wild flower both are nouns.

Word	Noun	Adjective	Verb	Adverb
rock penstemon	Yes	No	No	No
wild flower	Yes	No	No	No

As nouns, wild flower is a hypernym of rock penstemon; that is, wild flower is a word with a broader meaning than rock penstemon:

rock penstemon: one of the West's most beautiful wildflowers; large brilliant pink or rose flowers in many racemes above thick mats of stems and leaves; ledges and cliffs from Washington to California
wild flower: wild or uncultivated flowering plant

Other hypernyms of rock penstemon include wildflower.

rock penstemon (noun)	wild flower (noun)
one of the West's most beautiful wildflowers; large brilliant pink or rose flowers in many racemes above thick mats of stems and leaves; ledges and cliffs from Washington to California	wild or uncultivated flowering plant