silver-leaved poplar vs poplar

silver-leaved poplar and poplar both are nouns.

Word	Noun	Adjective	Verb	Adverb
silver-leaved poplar	Yes	No	No	No
poplar	Yes	No	No	No

As nouns, poplar is a hypernym of silver-leaved poplar; that is, poplar is a word with a broader meaning than silver-leaved poplar:

silver-leaved poplar: a poplar that is widely cultivated in the United States; has white bark and leaves with whitish undersurfaces
poplar: any of numerous trees of north temperate regions having light soft wood and flowers borne in catkins

Other hypernyms of silver-leaved poplar include poplar tree.

silver-leaved poplar (noun)	poplar (noun)
a poplar that is widely cultivated in the United States; has white bark and leaves with whitish undersurfaces	any of numerous trees of north temperate regions having light soft wood and flowers borne in catkins
	soft light-colored non-durable wood of the poplar