sweet bells vs shrub

sweet bells and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweet bells	Yes	No	No	No
shrub	Yes	No	No	No

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

sweet bells: bushy deciduous shrub of the eastern United States with long racemes of pinkish flowers
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of sweet bells include bush.

sweet bells (noun)	shrub (noun)
bushy deciduous shrub of the eastern United States with long racemes of pinkish flowers	a low woody perennial plant usually having several major stems