silky willow vs willow tree

silky willow and willow tree both are nouns.

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

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

silky willow: North American willow with greyish silky pubescent leaves that usually blacken in drying
willow tree: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of silky willow include willow.

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

silky willow: small shrubby tree of western North America (Alaska to Oregon)
willow tree: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of silky willow include willow.

silky willow (noun)	willow tree (noun)
North American willow with greyish silky pubescent leaves that usually blacken in drying	any of numerous deciduous trees and shrubs of the genus Salix
small shrubby tree of western North America (Alaska to Oregon)