witch hazel plant vs shrub

witch hazel plant and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
witch hazel plant	Yes	No	No	No
shrub	Yes	No	No	No

As nouns, shrub is a hypernym of witch hazel plant; that is, shrub is a word with a broader meaning than witch hazel plant:

witch hazel plant: any of several shrubs or trees of the genus Hamamelis; bark yields an astringent lotion
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of witch hazel plant include bush.

witch hazel plant (noun)	shrub (noun)
any of several shrubs or trees of the genus Hamamelis; bark yields an astringent lotion	a low woody perennial plant usually having several major stems