red osier dogwood vs dogwood

red osier dogwood and dogwood both are nouns.

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

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

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

Other hypernyms of red osier dogwood include cornel, dogwood tree.

red osier dogwood (noun)	dogwood (noun)
common North American shrub with reddish purple twigs and white flowers	a tree of shrub of the genus Cornus often having showy bracts resembling flowers
	hard tough wood of any dogwood of the genus Cornus; resembles boxwood