Erica arborea vs erica

Erica arborea and erica both are nouns.

Word	Noun	Adjective	Verb	Adverb
Erica arborea	Yes	No	No	No
erica	Yes	No	No	No

As nouns, erica is a hypernym of Erica arborea; that is, erica 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
erica: any plant of the genus Erica

Other hypernyms of Erica arborea include true heath.

Erica arborea (noun)	erica (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