red osier vs dogwood tree

red osier and dogwood tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
red osier	Yes	No	No	No
dogwood tree	Yes	No	No	No

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

red osier: common North American shrub with reddish purple twigs and white flowers
dogwood tree: a tree of shrub of the genus Cornus often having showy bracts resembling flowers

Other hypernyms of red osier include cornel, dogwood.

red osier (noun)	dogwood tree (noun)
Eurasian osier having reddish or purple twigs and bark rich in tannin	a tree of shrub of the genus Cornus often having showy bracts resembling flowers
common North American shrub with reddish purple twigs and white flowers