cascade penstemon vs Penstemon

cascade penstemon and Penstemon both are nouns.

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

cascade penstemon (noun)	Penstemon (noun)
whorls of deep blue to dark purple flowers at tips of erect leafy stems; moist places from British Columbia to Oregon	large genus of subshrubs or herbs having showy blue or purple or red or yellow or white flowers; mostly western North America