Erica arborea vs true heath

Erica arborea and true heath both are nouns.

Word	Noun	Adjective	Verb	Adverb
Erica arborea	Yes	No	No	No
true heath	Yes	No	No	No

As nouns, true heath is a hypernym of Erica arborea; that is, true heath is a word with a broader meaning than Erica arborea:

Erica arborea: evergreen treelike Mediterranean shrub having fragrant white flowers in large terminal panicles and hard woody roots used to make tobacco pipes
true heath: any plant of the genus Erica

Other hypernyms of Erica arborea include erica.

Erica arborea (noun)	true heath (noun)
evergreen treelike Mediterranean shrub having fragrant white flowers in large terminal panicles and hard woody roots used to make tobacco pipes	any plant of the genus Erica