flannel bush vs shrub

flannel bush and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
flannel bush	Yes	No	No	No
shrub	Yes	No	No	No

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

flannel bush: any of several handsome evergreen shrubs of California and northern Mexico having downy lobed leaves and showy yellow flowers
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of flannel bush include bush.

flannel bush (noun)	shrub (noun)
any of several handsome evergreen shrubs of California and northern Mexico having downy lobed leaves and showy yellow flowers	a low woody perennial plant usually having several major stems