shrubby penstemon vs lowbush penstemon

shrubby penstemon and lowbush penstemon both are nouns.

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

As nouns, shrubby penstemon and lowbush penstemon are synonyms defined as:

shrubby penstemon and lowbush penstemon: low bushy plant with large showy pale lavender or blue-violet flowers in narrow clusters at ends of stems

Other synonyms of shrubby penstemon include Penstemon fruticosus.

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