Australian heath vs shrub

Australian heath and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
Australian heath	Yes	No	No	No
shrub	Yes	No	No	No

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

Australian heath: any heathlike plant of the family Epacridaceae; most are of the Australian region
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of Australian heath include bush.

Australian heath (noun)	shrub (noun)
any heathlike plant of the family Epacridaceae; most are of the Australian region	a low woody perennial plant usually having several major stems