downy birch vs Betula pubescens

downy birch and Betula pubescens both are nouns.

Word	Noun	Adjective	Verb	Adverb
downy birch	Yes	No	No	No
Betula pubescens	Yes	No	No	No

As nouns, downy birch and Betula pubescens are synonyms defined as:

downy birch and Betula pubescens: European birch with dull white to pale brown bark and somewhat drooping hairy branches

Other synonyms of downy birch include white birch.

downy birch (noun)	Betula pubescens (noun)
European birch with dull white to pale brown bark and somewhat drooping hairy branches	European birch with dull white to pale brown bark and somewhat drooping hairy branches