creeping willow vs willow tree

creeping willow and willow tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
creeping willow	Yes	No	No	No
willow tree	Yes	No	No	No

As nouns, willow tree is a hypernym of creeping willow; that is, willow tree is a word with a broader meaning than creeping willow:

creeping willow: small trailing bush of Europe and Asia having straggling branches with silky green leaves of which several varieties are cultivated
willow tree: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of creeping willow include willow.

creeping willow (noun)	willow tree (noun)
small trailing bush of Europe and Asia having straggling branches with silky green leaves of which several varieties are cultivated	any of numerous deciduous trees and shrubs of the genus Salix