hoary golden bush vs shrub

hoary golden bush and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
hoary golden bush	Yes	No	No	No
shrub	Yes	No	No	No

As nouns, shrub is a hypernym of hoary golden bush; that is, shrub is a word with a broader meaning than hoary golden bush:

hoary golden bush: western American shrubs having white felted foliage and yellow flowers that become red-purple
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of hoary golden bush include bush.

hoary golden bush (noun)	shrub (noun)
western American shrubs having white felted foliage and yellow flowers that become red-purple	a low woody perennial plant usually having several major stems