Cornus obliqua vs dogwood tree

Cornus obliqua and dogwood tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cornus obliqua	Yes	No	No	No
dogwood tree	Yes	No	No	No

As nouns, dogwood tree is a hypernym of Cornus obliqua; that is, dogwood tree is a word with a broader meaning than Cornus obliqua:

Cornus obliqua: shrub of eastern North America closely resembling silky cornel
dogwood tree: a tree of shrub of the genus Cornus often having showy bracts resembling flowers

Other hypernyms of Cornus obliqua include cornel, dogwood.

Cornus obliqua (noun)	dogwood tree (noun)
shrub of eastern North America closely resembling silky cornel	a tree of shrub of the genus Cornus often having showy bracts resembling flowers