white poplar vs white aspen

white poplar and white aspen both are nouns.

Word	Noun	Adjective	Verb	Adverb
white poplar	Yes	No	No	No
white aspen	Yes	No	No	No

As nouns, white poplar and white aspen are synonyms defined as:

white poplar and white aspen: a poplar that is widely cultivated in the United States; has white bark and leaves with whitish undersurfaces

Other synonyms of white poplar include abele, aspen poplar, Populus alba, silver-leaved poplar.

white poplar (noun)	white aspen (noun)
a poplar that is widely cultivated in the United States; has white bark and leaves with whitish undersurfaces	a poplar that is widely cultivated in the United States; has white bark and leaves with whitish undersurfaces
light easily worked wood of a tulip tree; used for furniture and veneer