redwood penstemon vs shrub

redwood penstemon and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
redwood penstemon	Yes	No	No	No
shrub	Yes	No	No	No

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

redwood 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 redwood penstemon include bush.

redwood 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