bearberry willow vs willow tree

bearberry willow and willow tree both are nouns.

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

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

bearberry willow: dwarf prostrate mat-forming shrub of Arctic and alpine regions of North America and Greenland having deep green elliptic leaves that taper toward the base
willow tree: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of bearberry willow include willow.

bearberry willow (noun)	willow tree (noun)
dwarf prostrate mat-forming shrub of Arctic and alpine regions of North America and Greenland having deep green elliptic leaves that taper toward the base	any of numerous deciduous trees and shrubs of the genus Salix