poplar vs flowering tree

poplar and flowering tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
poplar	Yes	No	No	No
flowering tree	Yes	No	No	No

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

poplar: any of numerous trees of north temperate regions having light soft wood and flowers borne in catkins
flowering tree: any tree having seeds and ovules contained in the ovary

Other hypernyms of poplar include angiospermous tree.

poplar (noun)	flowering tree (noun)
any of numerous trees of north temperate regions having light soft wood and flowers borne in catkins	any tree having seeds and ovules contained in the ovary
soft light-colored non-durable wood of the poplar