Salix discolor vs willow tree

Salix discolor and willow tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Salix discolor	Yes	No	No	No
willow tree	Yes	No	No	No

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

Salix discolor: small willow of eastern North America having greyish leaves and silky catkins that come before the leaves
willow tree: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of Salix discolor include willow.

Salix discolor (noun)	willow tree (noun)
small willow of eastern North America having greyish leaves and silky catkins that come before the leaves	any of numerous deciduous trees and shrubs of the genus Salix