Prunus subcordata vs plum tree

Prunus subcordata and plum tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Prunus subcordata	Yes	No	No	No
plum tree	Yes	No	No	No

As nouns, plum tree is a hypernym of Prunus subcordata; that is, plum tree is a word with a broader meaning than Prunus subcordata:

Prunus subcordata: shrub of the Pacific coast of the United States bearing small red insipid fruit
plum tree: any of several trees producing edible oval fruit having a smooth skin and a single hard stone

Other hypernyms of Prunus subcordata include plum.

Prunus subcordata (noun)	plum tree (noun)
shrub of the Pacific coast of the United States bearing small red insipid fruit	any of several trees producing edible oval fruit having a smooth skin and a single hard stone