Canada plum vs plum tree

Canada plum and plum tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Canada plum	Yes	No	No	No
plum tree	Yes	No	No	No

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

Canada plum: small tree native to northeastern North America having oblong orange-red fruit
plum tree: any of several trees producing edible oval fruit having a smooth skin and a single hard stone

Other hypernyms of Canada plum include plum.

Canada plum (noun)	plum tree (noun)
small tree native to northeastern North America having oblong orange-red fruit	any of several trees producing edible oval fruit having a smooth skin and a single hard stone