cascade penstemon vs Penstemon serrulatus

cascade penstemon and Penstemon serrulatus both are nouns.

Word	Noun	Adjective	Verb	Adverb
cascade penstemon	Yes	No	No	No
Penstemon serrulatus	Yes	No	No	No

As nouns, cascade penstemon and Penstemon serrulatus are synonyms defined as:

cascade penstemon and Penstemon serrulatus: whorls of deep blue to dark purple flowers at tips of erect leafy stems; moist places from British Columbia to Oregon

cascade penstemon (noun)	Penstemon serrulatus (noun)
whorls of deep blue to dark purple flowers at tips of erect leafy stems; moist places from British Columbia to Oregon	whorls of deep blue to dark purple flowers at tips of erect leafy stems; moist places from British Columbia to Oregon