red shrubby penstemon vs shrub

red shrubby penstemon and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
red shrubby penstemon	Yes	No	No	No
shrub	Yes	No	No	No

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

red shrubby penstemon: low branching dark green shrub with bunches of brick-red flowers at ends of branches; coastal ranges and foothills of northern California
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of red shrubby penstemon include bush.

red shrubby penstemon (noun)	shrub (noun)
low branching dark green shrub with bunches of brick-red flowers at ends of branches; coastal ranges and foothills of northern California	a low woody perennial plant usually having several major stems