purple pea vs shrub

purple pea and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
purple pea	Yes	No	No	No
shrub	Yes	No	No	No

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

purple pea: any of several attractive evergreen shrubs of Australia grown for their glossy deep green foliage and flowers in rich blues and intense violets
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of purple pea include bush.

purple pea (noun)	shrub (noun)
any of several attractive evergreen shrubs of Australia grown for their glossy deep green foliage and flowers in rich blues and intense violets	a low woody perennial plant usually having several major stems